Science Fundamentals 2 - Life Science - Humans: Quickstudy Laminated Reference & Study Guide 1423249380, 9781423249382

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SCIENCE Life Science - Humans 2 WORLD’S #1 ACADEMIC OUTLINE

FUNDAMENTALS

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• The human body is a single organism made up of many systems: − Circulatory/ Cardiovascular − Digestive/Excretory

What Is the

Human Body?

− Endocrine − Immune/Lymphatic − Integumentary − Muscular − Nervous − Renal/Urinary

− Reproductive − Respiratory − Skeletal • Humans, like all living organisms: − Are made of cells

− Obtain food to make energy − Grow and develop − Reproduce − Respond and adapt to their environment

HIERARCHICAL ORGANIZATION Cells • • • • •

The building blocks of all life Microscopic Not all animal (human) cells look alike Structure mirrors cell function Cells have a specialized purpose in the human body

Tissues • Groupings of cells of the same type • Four primary types: 1. Connective: bind cells and organs together 2. Epithelial: cover the exterior of the body, internal cavities, and some glands 3. Muscle: provide movement 4. Nervous: send electrochemical signals throughout the body

Organs • Different types of tissues organized together to perform a complex function • An organ may have more than one function • Largest organ in the human body is the skin. The tissues work together to:

ORGANS

− Produce hormones; regulate temperature; retain fluids; sense heat, pain, pressure

Thyroid

GLANDS • Organs that secrete substances into the bloodstream or remove material from blood − Endocrine: release substances into the bloodstream EX: pituitary, thyroid, testes, ovaries − Exocrine: release substances to the exterior or into body cavities EX: sweat glands, mammary glands, liver, pancreas

Organ System

Brain Heart

Lungs Stomach Liver

Kidneys

Intestines

• Group of organs working together • Performs complex functions • May work with other systems to keep the body healthy • Necessary for survival (except for reproductive system) • 11 organ systems in the human body

Bladder

Did You Know? • Vestigial organs have no clear function and are remnants from ancestral evolution (e.g., wisdom teeth, appendix)

ORGAN SYSTEMS OF THE HUMAN BODY CIRCULATORY/CARDIOVASCULAR SYSTEM ESSENTIAL FUNCTIONS • • • •

Transports oxygen and nutrients throughout body Removes carbon dioxide and other wastes Allows blood to flow under a certain pressure Works with the lungs

PARTS • Heart • Blood (which is a tissue) • Blood vessels

− Red blood cells: carry oxygen and give blood its color − Platelets: help blood clot (along with red blood cells) − White blood cells: fight germs (as part of the immune system)

Heart

Aorta Superior vena cava

Pulmonary artery Pulmonary vein

Arterial system

• Takes blood from the heart to the body • Arteries, arterioles, capillaries • Aorta: main artery

Venous system

• Takes blood back to the heart • Veins and venules

HOW IT ALL WORKS TOGETHER Blood • Made of plasma, red blood cells, platelets, and white blood cells • Circulates electrolytes, oxygen, carbon dioxide, and amino acids throughout body • Classified according to type: A, B, AB, and O • Contains: − Plasma: carries chemicals, waste, and warmth around the body

Right atrium

Left atrium

Tricuspid valve

Mitral valve

Pulmonary valve Right ventricle

Aortic valve Left ventricle

Septum

• One of the strongest muscles in the human body • Made of two halves divided into four chambers: − Upper two chambers: atria − Lower two chambers: ventricles • Found in chest cavity, surrounded by the pericardium, a fluid-filled sac • Valves allow for flow of blood in only one direction • Arteries and veins connect the heart to other parts of the body 1

How the system works 1. Circulation of blood begins when heart is between beats 2. Blood moves from both atria to both ventricles 3. Left ventricle pumps blood, rich in oxygen, into the aorta 4. Oxygenated blood travels from main artery to smaller and smaller arteries and then into capillaries 5. Blood leaves oxygen and nutrients at the capillaries and picks up carbon dioxide and waste materials 6. Blood, now low in oxygen, moves into veins and travels to right atrium and into right ventricle 7. Right ventricle pumps the low-oxygen blood into the pulmonary artery, which also breaks into smaller and smaller arteries and capillaries 8. Capillaries surround pulmonary vesicles, which are small sacs at the end of an airway 9. Here, carbon dioxide is released into pulmonary vesicles, and fresh oxygen enters the blood 10. Exhaling releases the carbon dioxide into the air 11. Newly oxygenated blood travels through pulmonary veins to left atrium 12. Blood then flows into the left ventricle, and the cycle begins again

Did You Know? • The heart usually pumps about 1 gallon of blood per minute • When you exercise, it can pump 7 gallons a minute

DIGESTIVE SYSTEM ESSENTIAL FUNCTIONS • Digestion: breaks food down into small molecules • Absorption: moves those small molecules through intestine wall − Molecules enter into blood or lymph (fluid composed of white blood cells)

PARTS • Digestive tract or alimentary canal − Continuous tube with two openings: the mouth and anus − Includes: mouth, pharynx, esophagus, stomach, small intestine, large intestine • Accessory organs − Include teeth and tongue, salivary glands, liver, gallbladder, pancreas

HOW IT ALL WORKS TOGETHER Mouth • Mechanical digestion begins as teeth chew food into smaller pieces (mastication) • Some teeth grind food; others tear it • Tongue moves food around mouth • Salivary glands secrete enzymes that start chemical digestion

Pharynx

• Site of swallowing • Leads to esophagus

Epiglottis

• Flap in throat preventing food from entering trachea (windpipe)

Esophagus

• Connects pharynx and stomach • Smooth muscle contracts and relaxes to move food forward (peristalsis)

Stomach

• Holds food that passes from esophagus • Stores food before digestion • Secretes enzymes and hydrochloric acid (HCl) to aid in chemical digestion − Secretes nearly 2 liters of HCl each day • Regulates movement of food into small intestine • Site of chemical digestion, especially proteins • Food stays in stomach for 3–4 hours, partially digested, before moving to small intestine

ENDOCRINE SYSTEM ESSENTIAL FUNCTIONS

ENDOCRINE SYSTEM GLANDS

• Monitors hormones in the blood • Produces and releases hormones based on body needs • Maintains homeostasis in the body. The pituitary gland: − Senses when more or less hormones are needed − Directs the other glands to compensate

Gland(s)

PARTS

ovaries

adrenals

.

hypothalamus

Endocrine disruptors (chemicals found in pesticides, plastics, and some cosmetics) change the way hormones send messages

• Hormones • Glands

HOW IT ALL WORKS TOGETHER

pancreas

Hormones • Chemicals that carry messages through the blood to organs for different functions • Signals that tell the body what to do during: − Growth and development − Metabolism • They also regulate: − Blood pressure − Fertility − Mood − Sexual function − Sleep

Glands

• Controlled by the nervous system • Release hormones into the bloodstream

parathyroid pineal pituitary

testes thyroid

Largest solid organ Removes toxins from blood Regulates blood clotting Produces bile and moves it to gallbladder − Bile helps digest lipids in small intestine

Pancreas

• Produces enzymes that help with digestion • Sends out hormones that help regulate sugar in bloodstream

Large intestine (colon)

• Takes material not absorbed by small intestine (few nutrients; only water, undigested food, and cellulose) • Absorbs water for stool formation

Rectum

• Lowest part of large intestine • Holds stool until it is passed from the body out the anus

Did You Know? • Stretched out, the intestines are more than 25 feet long

one on top of each kidney

brain

lower abdomen of females abdomen, near stomach next to thyroid at front of neck brain base of brain

male scrotum front of neck

• Immune cells form in bone marrow

Antibiotics help the immune system fight infections caused by bacteria, not viruses

Tonsils & adenoids

Innate immune system

• Born with it; inherited • Made of skin, cornea, mucous membranes • Creates physical barriers to germs, particles, or cancerous cells

Thymus Axillary lymph nodes

Bone marrow

Adaptive immune system

• Develops with exposure to microbes or chemicals • The body makes special antibodies (proteins) that protect against specific threats • Developed by cells called B lymphocytes as a result of exposure to a threat Spleen • Includes organs such as: − Adenoids − Bone marrow − Lymph nodes − Spleen Inguinal − Tonsils lymph

Peyer’s patch

Gallbladder

• Stores and releases bile into duodenum

Location

IMMUNE & LYMPHATIC SYSTEMS

Liver • • • •

• release adrenaline, which increases breathing and heart rate and controls blood pressure, metabolism, and response to stress • controls endocrine system • gathers information from central nervous system (CNS) and directs other glands to produce or slow hormones • controls mood, hunger/thirst, sleep, sexual function • release estrogen, progesterone, and testosterone (sex hormones), which change the female body as it grows older • regulate menstrual periods and pregnancy • releases insulin, which controls blood sugar levels • plays a role in digestive system • controls calcium level (needed for kidneys, bones, heart, and CNS to work effectively) • releases melatonin (hormone that makes you feel sleepy) • makes hormones that control other glands • controls growth and development • release testosterone, which changes the male body as it grows older • impact production of sperm, muscle strength, and sex drive • controls metabolism

Did You Know? • Type 1 diabetes, a condition where the pancreas does not make enough insulin, is an endocrine disorder

Small intestine

• Coiled in abdomen • Lined with villi, which increase surface area, so absorption is quicker • Consists of three parts: duodenum, jejunum, ileum − Duodenum takes in 9 liters of fluid a day; site of digestion − Jejunum and ileum are involved in absorption of smallest food molecules • Chemical digestion in small intestine relies on the accessory organs: liver, pancreas, gallbladder

Primary Function(s)

nodes Appendix

ESSENTIAL FUNCTIONS • Kill germs; fight disease

IMMUNE SYSTEM

• Cells and organs that: − Destroy pathogens that may cause death or disease − Prevent or limit infection 2

Parts

• Skin: first line of defense against microbes − Produces proteins that fight microbes • Bone marrow: contains stem cells, which can develop into different types of cells • Bloodstream: carries immune cells (white blood cells) throughout the body − Blood tests monitor white blood cells— too many or too few indicates a possible problem

LYMPHATIC SYSTEM

IMMUNE & LYMPHATIC SYSTEM FUNCTIONS

• System of vessels, cells, and organs that: − Carries fluids to the bloodstream − Removes pathogens from blood − Works closely with the immune system; in healthy people, these two systems work almost as one

Mechanism and/or Method acidic juices in stomach antibodies digestive & respiratory membranes

Parts

• Lymph nodes: communicate information from white blood cells − Swollen lymph nodes may indicate an immune system response • Spleen: organ behind stomach − Important for processing bloodstream information − Not directly part of the lymphatic system but plays a significant role − White blood cells are concentrated around the spleen and will react if pathogens in blood are detected • Mucous membranes: first line of defense against pathogens

Primary Function(s) • kill bacteria in food • destroy antigens • remember antigens so the body becomes immune to future infections • trap foreign particles in food and air • secrete antibodies in the presence of an antigen (virus, bacteria, etc.) • trap foreign particles in air • keeps water, intruders, and foreign particles outside the body • destroy cell walls of bacteria

lymphocytes nose hair & respiratory cilia skin sweat, saliva & tears

Did You Know? • Allergies are the immune system’s inappropriate response to harmless substances

INTEGUMENTARY SYSTEM ESSENTIAL FUNCTIONS • Outer layer of the body; acts as a physical barrier • Protects against bacteria, injury, and sunlight • Helps maintain homeostasis by regulating body temperature • Cushions the body • Secretes sweat and other body waste • Synthesizes vitamin D

PARTS

• Skin, hair, nails, glands

HOW IT ALL WORKS TOGETHER Skin • Largest, heaviest organ in the body − On average, 2 mm thick − Weighs about 3 kg (6 pounds) − 1 inch of skin could have 19 million cells

• Three major layers: 1. Epidermis: top layer of visible skin A. Waterproof barrier B. Gives skin its color 2. Dermis: middle, thicker layer A. Contains sweat and oil glands and hair follicles 3. Hypodermis: fatty, lower layer A. Insulates the body

• Muscles attached to hair follicles and skin contract to make hair stand up and cause goosebumps • Follicles come in different shapes, which determine hair type: − Kidney-shaped follicles create curly hair − Round follicles create straight hair − Oval follicles create wavy hair

Nails

Hair • • • •

• Protect ends of toes and fingers • Made of keratin (a type of protein) • Parts: − Nail plate: part of nail you can see − Nail bed: skin under the plate − Cuticle: skin at base of nail plate − Matrix: root of the nail; responsible for growth − Lunula: whitish, moon-shaped part of visible nail

Helps keep heat in the body Eyelashes and eyebrows protect eyes Made of keratin Three parts: 1. Shaft: the part you see 2. Follicle: tube-like structure that keeps hair in the skin 3. Bulb: located under skin, causes hair to grow

MUSCULAR SYSTEM ESSENTIAL FUNCTIONS • Gives the body strength • Controls movement of the body and its parts • Produces body heat • Aids in: − Circulation, childbirth, digestion, respiration, stability and posture, urination, vision • Works in conjunction with skeletal system • Muscles covering bones determine body shape

Tendons

• Attach muscle to bone • Absorb some of the impact of muscle movement • Tough, inelastic

MUSCLE CLASSES Visceral • In hollow internal organs (blood vessels, gastrointestinal tract, bladder, uterus) • Controlled by autonomic nervous system and therefore involuntary

Cardiac

• Found in walls of the heart • Involuntary

Skeletal

• Attached to bones

• Cause movement of skeleton • Controlled by CNS • Voluntary

MUSCLE TYPES Striated • Skeletal/voluntary • Move bone, face, eyes • Arranged in bundles

Smooth

• Visceral, involuntary, nonstriated • No conscious control • Found in blood vessels as well as internal organs • Form sheets of fiber that wrap around vessels

Cardiac

• Look striated but behave as if smooth • Form wall of heart • Control contractions that form heartbeat

HOW IT ALL WORKS TOGETHER • Muscles contract and move bones to enable movement − Point of attachment to bone is the origin or beginning of the muscle

Glands • Sudoriferous: secrete sweat through the skin through pores or into hair follicles • Sebaceous: produce oil, particularly on the face • Ceruminous: in ears; produce earwax • Mammary: on the chest; produce milk in females after childbirth

Did You Know? • Skin cells constantly form and replace old cells • We shed 40 million dead skin cells each day (that’s 45 pounds of skin over a lifetime) • We shed a pint of sweat each day • An adult body has about 3 million sweat glands

NERVOUS SYSTEM

− When a muscle contracts, the bone attached at its origin stays stationary − The other bone, attached at the insertion, moves − Near the insertion location, a tendon attaches the muscle to the bone • Muscles move and act on commands from the brain − Receive messages from the brain for every movement − These messages begin as electrical and chemical signals that travel down the spinal cord • Muscles have cells that store energy called ATP, which is made from food and oxygen

Did You Know? • The body has more than 600 muscles that help you move • 200 muscles work together for you to take one step • Muscles make up nearly 40% of body weight • Muscles can only pull, not push, so they must work in pairs • The biggest muscle is the gluteus maximus in the buttocks • The most powerful muscle, the masseter, is in the jaw 3

ESSENTIAL FUNCTIONS • Receives internal and external stimuli • Sends signals and messages to central processing center (brain) • Interprets and reacts to stimuli

Responsible for: • • • • • • • • • • • • •

Aging Body temperature Brain growth and development Breathing/heartbeat Healing Hunger, thirst, digestion Movement, balance Perceptions Puberty, fertility, reproductive health Sensations (touch, hearing) Sleep Stress and reactions to stress Thought, learning, memory

PARTS Central nervous system (CNS) • Brain and spinal cord • Controls: − Body temperature, breathing, emotion, heart rate, hormones, movement, thought • Cannot regenerate cells • Spinal column and brain protected in a triplelayered membrane called the meninges

Peripheral nervous system (PNS)

• All the nerves outside of the CNS • Much of the PNS can regenerate (regrow cells), if needed

• Somatic: voluntary EX: blinking eyelids, avoiding slipping and falling on a patch of ice • Autonomic: involuntary EX: heartbeats

HOW IT ALL WORKS TOGETHER Brain • Contains tangled web of neurons − Responsible for thinking, behavior, learning, and memory − Estimated 100 billion neurons, connected to thousands more • Linked to entire body via nerves • Uses about 20% of the oxygen we breathe • Protected by skull • Has four main lobes: 1. Temporal: processes senses and gives them emotional meaning; long-term memory 2. Parietal: translates sensory information, such as touch, spatial relationships, navigation 3. Occipital: processes vision 4. Frontal: responsible for attention, shortterm memory, motivation, planning • Divided into hemispheres: − Left half: » Controls right half of the body » Linked to language and mathematical abilities − Right half: » Controls left half of the body » Linked to musical and artistic abilities

Spinal cord

• Carries information between the brain and the rest of the body • Connects with nerves of PNS • 31 spinal nerves connect the spinal cord to the brain stem

RENAL/URINARY SYSTEM

NEURONS Type connector motor sensory

SENSES Sense

Primary Function(s) passes information between neurons sends instructions from the brain to various muscles

ESSENTIAL FUNCTIONS

sends information about (or received from) the senses to the brain

• Produces, stores, and excretes urine • Helps maintain water balance (homeostasis) in the body • Balances electrolytes • Assists in production of red blood cells • Filters wastewater from the body and chemicals from blood

Associated with: How It Works

feeling/ touch

• skin

hearing/ sound

• ears

seeing/ sight

• eyes

smelling/ smell

• nose

tasting/ taste

• tongue • mouth

Nerves

• skin contains touch sensors to recognize and interpret heat, cold, pressure, and pain • signals sent to brain where sensation is actually felt • sounds enter the ears and funnel through the ear canal • sounds vibrate the eardrum • vibrations, detected by small bones, send electrical signals to brain • brain interprets signals to understand sounds • eyes recognize light and send signals to brain • brain interprets signals to understand images • nose has sensitive patch of cells to detect smells • 200 million cilia (small, hair-like appendages) interpret smells and send messages to brain • tongue covered in taste buds, which contain sensitive nerve endings • signals sent to brain to interpret taste

PARTS • Two kidneys − Contain nephrons, which filter waste from blood and balance water, ions, and molecules − Cannot be replaced or regenerated − One kidney has enough nephrons to filter the body’s blood, which is why a person can donate a kidney • Two ureters • One bladder: stores and releases urine − Can store 300–600 milliliters of urine before urination • Two sphincters: located under the bladder − Only relax during urination, to keep urine from leaking out • One urethra

HOW IT ALL WORKS TOGETHER • Renal artery brings blood to kidneys • Kidneys filter blood, removing extra water, salts, and other small molecules • Undesired products move from each kidney through a ureter to the bladder • Filtered blood passes out of the kidney and returns to the rest of the circulatory system through the renal vein • Urine is stored in the bladder until the nervous system releases it through the urethra and out of the body. This is urination (or micturition)

Did You Know? • About 100 billion neurons inhabit the human body • There are more nerve cells in the human brain than there Senses are stars in the Milky Way galaxy • Include sight, sound, smell, taste, and touch • Signals sent through neurons can travel up to 270 mph • The semicircular canals in the ear also help the body • The brain’s tools for detecting and keep its balance understanding the world • Carry messages between the brain and the rest of the body • Composed of nerve cells called neurons

Did You Know? • All blood in the body passes through the kidneys 400 times each day • The human bladder can stretch to hold about 4 quarts of urine

REPRODUCTIVE SYSTEM ESSENTIAL FUNCTIONS • Responsible for reproduction and creation of new life

PARTS • Gonads: ovaries and testes • Gametes: sperm and egg cells

FEMALE REPRODUCTIVE SYSTEM • Oogenesis: production of ovum (an egg) in the ovaries • Vagina: canal leading from outside the body to the cervix • Cervix: opening of the uterus • Uterus (womb): internal organ that houses and nurtures fertilized zygote − During pregnancy a placenta surrounds the growing embryo that attaches to the uterine wall • Fallopian tubes: transport eggs from ovaries to uterus • Ovaries: produce female gametes (eggs) and hormones; one on each side of the uterus

MALE REPRODUCTIVE SYSTEM

• Male sperm cells join with female egg cells and create single fertilized cell (zygote)

• Spermatogenesis: sperm production; begins in the testes • Penis: main organ for sexual intercourse − Urethra stretches the length of the penis and lets urine or sperm pass through a small opening • Testes (testicles): produce male gametes (sperm) and sex hormones • Scrotum: external pouch of skin that holds testes and provides the proper temperature for sperm development

See Mitosis & Meiosis section (page 6) for more information about cell division and fertilization

Zygote/Embryo

Zygote Egg Blastocyst Inner cell

HOW IT ALL WORKS TOGETHER Sex cells • Female sex cells (eggs) form in ovaries • Male sex cells (sperm) form in testes

4

2-cell stage

4-cell stage Morula

• Undergoes initial mitotic division in fallopian tubes • Moves to uterus after 6–8 days, where most development occurs • Multiplies rapidly to form embryo, an organism in early stages of development

• Becomes fetus after internal organs have developed (about 8 weeks)

Fetus

• Develops inside the uterus for about 40 weeks • Attached to the uterus by the umbilical cord • Receives blood flow and nutrients via arteries and vein in umbilical cord • Surrounded by amniotic sac and placenta • Nourished and has waste removed by placenta • Travels out of the vagina during childbirth

Did You Know? • About 500 million sperm mature every day in a male adult • The ovaries of a newborn female contain about 600,000 immature eggs • The average life span of a sperm cell is about 36 hours

RESPIRATORY SYSTEM ESSENTIAL FUNCTIONS • • • •

Takes fresh air into the body Absorbs oxygen from the air Removes waste gases Network of organs and tissues that helps you: − Breathe − Talk and smell • Warms and adjusts humidity of air as it enters the body • Protects airways from irritants

PARTS • Mouth • Nose • Sinuses

• • • • •

Pharynx (throat) Trachea, larynx Lungs Diaphragm Ribs

HOW IT ALL WORKS TOGETHER

5. Branches to smaller bronchioles before they end at alveoli 6. Fills alveoli, where oxygen is extracted 7. Diaphragm muscle aids inhalation (intake of air)

Carbon dioxide:

1. Passes from alveoli to blood vessels 2. Is sent to the heart by cells in blood vessels 3. Is pumped to the rest of the body by the heart 4. Interacts with food particles to provide cells with usable energy

Did You Know? • Moving air through the larynx also allows us to make noises like talking and singing • The surface area of the lungs is about 160 square meters (about the same size as a tennis court) • The body breathes in about 13 pints of air every minute

Oxygen:

Air: 1. Enters mouth or nostrils and travels down the trachea 2. Is cleaned of dust and dirt as it passes over cilia in the trachea 3. Enters lungs through bronchi 4. Branches throughout lungs via bronchial tree

1. Is released by cells as a waste product after creating energy 2. Travels back through blood vessels to the lungs 3. Follows a reverse course from oxygen and is breathed out

SKELETAL SYSTEM ESSENTIAL FUNCTIONS • Gives the body shape and structure • Provides framework for muscles, ligaments, and tendons • Protects body parts (e.g., the skull protects the brain and ribs protect lungs and other organs) • Produces blood cells in marrow • Stores minerals and nutrients (calcium and vitamin D)

PARTS Bones • Form skeleton • Composed primarily of calcium phosphate and calcium carbonate • Living, growing tissue made of collagen and calcium • Storage site for calcium • 206 bones in an adult human • Three layers of bone: 1. Periosteum: covers outside of bone A. Protection B. Tough membrane 2. Compact bone: beneath periosteum A. White, hard, and smooth B. Provides structure 3. Spongy bone: inner layer A. Small pores to hold marrow

Joints

• Major bones: − Carpals − Clavicle − Femur − Fibula − Humerus − Patella − Pelvis − Radius − Ribs − Scapula − Sternum − Skull (30 separate bones) − Tarsals − Tibia − Ulna − Vertebral column (33 vertebrae)

• Located where two or more bones come together • Lubricated by synovial fluid • Immovable joints: do not allow bones to move EX: bones in the skull • Partly movable joints: allow limited movement EX: rib cage • Movable joints: wide range of motion EX: elbows, shoulders, knees JOINT TYPES Type Found in: ball-andsocket cartilaginous gliding hinged

Cartilage

pivot

• Flexible material covering ends of bones where they meet − Prevents friction • Can wear away with time and conditions like arthritis, which can lead to pain and other problems

• shoulders • hips • vertebrae • wrist • fingers • elbows • knees • ankles • top of neck

Ligaments • • • •

Allows Bones to: move in nearly any direction

twist and bend slide over each other swing like a door hinge rotate against each other

Did You Know?

Attach bone to bone • Babies are born with Give stability to joints up to 270 bones Tough, inelastic Make up about 20% of a person’s weight

GENETICS WHAT IS GENETICS? • The study of heredity (genes and chromosomes), which determines inherited traits • Passage of traits from parents to offspring • Genetics focuses on the study of DNA molecules

DNA • Every cell contains chromosomes that contain DNA, the special code for the genes that determines nearly everything about our bodies • Through reproduction, each parent’s DNA gets passed on to children • Specific features are passed on, but generations are not identical • Chromosomes are packed

inside the cell nucleus • Humans have the same 46 chromosomes in each nucleus • Most cells are diploid, meaning they contain two sets of chromosomes − Each set contains 23 matching homologous pairs − Each set carries the code for 30,000–40,000 genes

Cy tosine

− Genes occur in the same order along both chromosomes of a pair − Therefore, genes also occur in pairs • Sex is determined by one set of 46 chromosomes − Sex chromosomes are classified as either X or Y, based on their appearance − Females have two X chromosomes (XX)

Guanine

Adenine

− Males have one X and one Y chromosome (XY) − Sex cells (gametes) are an exception » Female egg cells contain only one X chromosome » Male sperm cells contain either one X or one Y chromosome » Y chromosome has the genetic code to develop male offspring

ALLELES • Different versions of a DNA sequence • Appear through • Produce the variations that make mutations individuals unique • Humans inherit • Determine which traits a person will two alleles, one have from each parent 5

• If the alleles from each parent are: B B b b B b b B − Identical: offspring is homozygous for trait − Different: offspring is Homozygous Heterozygous heterozygous for trait

Alleles (continued) • During the 19th century, Gregor Mendel experimented with pea plants and discovered that traits were dominant or recessive − Recessive traits only manifest when a person has two recessive alleles • Phenotype: the actual appearance of an organism • Genotype: the genes that influence this appearance

PUNNETT SQUARES

• When a homozygous dominant parent (AA) and a homozygous recessive parent (aa) reproduce, the Punnett square shows that the offspring will all: − Have a heterozygous genotype (Aa) − Show the dominant phenotype • If two heterozygous parents (Aa) reproduce: − 25% of the offspring will be homozygous dominant (AA)

AA × aa Aa × Aa a a A a A Aa Aa A AA Aa A Aa Aa a Aa aa • Used by geneticists to predict genotypes and phenotypes

MITOSIS & MEIOSIS Essential Knowledge • Cells divide and reproduce one of two ways: 1. Mitosis: nucleus divides and number of chromosomes stays the same 2. Meiosis: nucleus divides and number of chromosomes is halved

MITOSIS

Interphase

Prophase

Metaphase

Cytokinesis

Telophase

Anaphase

Cell membrane Centrosomes Nucleolus Cytoplasm Chromosome Nucleus Nuclear membrane

MEIOSIS I Stage Daughter chromosomes

• DNA duplicated and divided between two new daughter cells • Chromosomes form two linked strands (chromatids) joined at a centromere • Occurs in a set of steps called the cell cycle

prophase I

Cell cycle

Activity

• chromosomes replicate to form chromatids • chromosomes pair with homologues • crossing over between matching pairs may occur (chromosomes share pieces and create new chromosomes with unique genetic pattern) • chromosome pairs line up in center of cell • homologous pairs separate and move apart • chromatids collect at opposite sides of cell • new nuclear membrane forms around each group • two daughter cells form; sister chromatids stay together

• Interphase: period of cell growth − Most cells spend about 90% of their time in this phase • Prophase: chromatin condenses into two distinct chromosomes − Each chromosome has two chromatids with a centromere − Spindles form in cytoplasm − Centrioles move to different ends of cell • Metaphase: nuclear membrane disappears − Chromatids line up in center of cell • Anaphase: paired chromosomes separate and move to opposite sides of cell − This “full” chromosome is called a “daughter” chromosome − Cell lengthens, as each pole of the cell has a complete set of chromosomes • Telophase: new nuclear membrane forms around each pole • Cytokinesis: division of cytoplasm − Begins before end of anaphase − Completed at end of telophase − Results in two identical diploid daughter cells, each having a full set of chromosomes

metaphase I

MEIOSIS

Did You Know? • When a fertilized egg splits, identical twins develop • When two eggs are fertilized by two sperm, fraternal twins develop

• Cells divide to form sex cells (gametes) with only 23 chromosomes (haploid cell) • Male sperm cells form in testes

anaphase I

telophase I

MEIOSIS II Stage Activity prophase II metaphase II anaphase II

telophase II prophase II– telophase II

• chromosomes move to metaphase II stage • they do not replicate • chromosomes line up • sister chromatids separate and begin to move to different ends of cell • cell stretches • new nucleus forms around daughter chromosomes • cytoplasm divides • two new cells form during cytokinesis • resembles ordinary mitosis

U.S. $6.95 Author: Jane Parks Gardner, MSc, MScEd

NOTE TO STUDENT: This guide is intended for informational purposes only. Due to its condensed format, this guide cannot cover every aspect of the subject; rather, it is intended for use in conjunction with coursework and assigned texts. Neither BarCharts, Inc., its writers, editors nor design staff, are in any way responsible or liable for the use or misuse of the information contained in this guide. All rights reserved. No part of this publication may be reproduced or transmitted in any form, or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without written permission from the publisher. Follow Made in the USA ©2023 BarCharts, Inc. 0523 BarCharts, Inc.

Did You Know? • All humans have 99.9 percent identical genes • The 0.1 percent difference creates all existing variety and diversity • A cytologist studies cells, and a geneticist studies genes and DNA

DNA, RNA & PROTEINS

• Female egg cells form in ovaries • Ensures the correct number of chromosomes will be given to each cell during sexual reproduction − Haploid gametes form a diploid cell (zygote) − Once fertilized, a human zygote has 46 chromosomes • Also results in genetic variation due to genetic recombination with homologous chromosomes • The original cell produces four daughter cells − These daughter cells each have only half the number of chromosomes • Two general phases: meiosis I and meiosis II

Daughter cells

− 50% will be heterozygous (Aa) − 25% will be homozygous recessive (aa)

DNA • Most DNA (deoxyribonucleic acid) is located inside the nucleus of a cell • Mitochondrial DNA (mtDNA) is found inside the mitochondria • Composed of millions of nucleotides − A nucleotide is composed of a sugar, a phosphate, and a chemical base • Resembles a twisted ladder with four chemical bases as rungs: 1. Adenine (A) 2. Cytosine (C) 3. Guanine (G) 4. Thymine (T) − Adenine and thymine always combine − Cytosine and guanine always combine • Shape is called a double helix • Can self-replicate − “Unzips” to form two separate strands with one half of each base pair − Free nucleotides attach to unzipped bases and form two new complete strands • Groups of three bases are known as a codon − Codons are analogous to a genetic “word” EX: ACG, TCA − There are 64 different codons that compose the genetic code

RNA • RNA (ribonucleic acid) assists in protein synthesis and translating the genetic code • DNA unzips to form singlestrand RNA • Free nucleotides pair with the unzipped bases − In RNA the chemical base thymine is replaced with uracil » Uracil acts the same as thymine » Adenine and uracil always combine • Messenger RNA (mRNA) carries the genetic code for a protein hundreds of titles at

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− Travels through nuclear membrane to cytoplasm − Attaches to ribosome, which decodes message and builds protein with amino acids • Transfer RNA (tRNA) carries amino acids to ribosome and mRNA − Contains bases to match codons on mRNA − Bases join, and amino acids are joined together with enzymes − Amino acids form a chain and produce a new protein

Proteins • Form part of nearly everything in the body • Direct the development of all types of cells and cellular activities • Made of 20 different types of amino acids − Each protein is composed of a specific order of amino acids − This order is determined by genes in DNA • Made in the cytoplasm of a cell − DNA is too big to permeate the nuclear membrane

Did You Know?

• The 46 chromosomes in each cell contain 6 feet of DNA • If the total DNA in one person was laid in a straight line, it would stretch to the Sun and back more than 30 times • Evolution is the naturally occurring change in inherited traits over generations − It progresses as a result of natural selection and mutation • Charles Darwin suggested that species changed to adapt to surroundings − He called this “survival of the fittest” • In 1944, Oswald Avery proved that DNA carried genetic instructions • In 1953, James Watson and Francis Crick discovered the double-helix construction