Chapter 18: Animal Diversity
18.1 What is an animal?
• Animals are eukaryotic, multicellular heterotrophs
– That ingest their food
• Animal development
– May include a blastula, gastrula, and lar val stage
18.2 The ancestor of animals was probably a colonial, flagellated protist
• Cells in these protists
– Gradually became more specialized and layered
18.3 Animals can be characterized by basic features of their “body plan”
• Animal body plans
– May vary in symmetr y
– Vary in body cavity
– Development as either protostomes or deuterostomes
18.4 The body plans of animals can be used to build phylogenetic trees
• One hypothesis of animal phylogeny
– Is based on morphological comparisons
18.5 Sponges have a relatively simple, porous body
• Sponges, phylum Porifera
– Are the simplest animals and have no true tissues
• Flagellated choanocytes
– Filter food from the water passing through the porous body
18.6 Cnidarians are radial animals with tentacles and stinging cells
• Cnidarians, phylum Cnidaria
– Have true tissues and radial symmetry
• Their two body forms are
– Polyps, such as hydra
– Medusae, the jellies
• They have a gastrovascular cavity
– And cnidocytes on tentacles that sting prey
18.7 Flatworms are the simplest bilateral animals
• Flatworms, phylum Platyhelminthes
– Are bilateral animals with no body cavity
• A planarian has a gastrovascular cavity
– And a simple nervous system
• Flukes and tapeworms
– Are parasitic flatworms with complex life cycles
18.8 Nematodes have a pseudocoelom and a complete digestive tract
• Nematodes, phylum Nematoda
– Have a pseudocoelom and a complete digestive tract
• Many nematodes are free-living
– And others are plant or animal parasites
18.9 Diverse molluscs are variations on a common body plan
• All molluscs have a muscular foot and a mantle
– Which may secrete a shell that encloses the visceral mass
• Many mollusks
–
Gastropods
•
Feed with a rasping radula
Gastropods are the largest group of molluscs
– And include the snails and slugs
Bivalves
•
The bivalves have shells divided into two halves
– And include clams, oysters, mussels, and scallops
Cephalopods
• Cephalopods are adapted to be agile predators
– And include squids and octopuses
18.10 Annelids are segmented worms
• The segmented bodies of phylum Annelida
– Give them added mobility for swimming and burrowing
Ear thworms and Their Relatives
• Ear thworms
– Eat their way through soil
– Have a closed circulatory system
Polychaetes
• The polychaetes
– Form the largest group of annelids
– Search for prey on the seafloor or live in tubes and filter food par
ticles
Leeches
• Most leeches
– Are free-living carnivores, but some suck blood
18.11 Ar thropods are segmented animals with jointed appendages and an exoskeleton
• The diversity and success of ar thropods
– Are largely related to their segmentation, exoskeleton, and jointed
appendages
Chelicerates
• Chelicerates include
– Horseshoe crabs
– Arachnids, such as spiders, scorpions, mites, and ticks
Millipedes and Centipedes
• Millipedes and centipedes
– Are identified by the number of jointed legs per body segment
Crustaceans
• The crustaceans
– Are nearly all aquatic
– Include crabs, shrimps, and barnacles
18.12 Insects are the most diverse group of organisms
• Insects have a three-par t body consisting of
– Head, thorax, and abdomen
– Three sets of legs
– Wings (most, but not all insects)
• Many insects undergo
– Incomplete or complete metamorphosis
18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for
movement
• Echinoderms, phylum Echinodermata
– Includes organisms such as sea stars and sea urchins
– Are radially symmetrical as adults
• The water vascular system
– Has suction cup–like tube feet used for respiration and locomotion
18.14 Our own phylum, Chordata, is distinguished by four features
• Chordates, phylum Chordata have
– A dorsal hollow ner ve cord
– A stiff notochord
– Pharyngeal slits
– A muscular post-anal tail
• The simplest chordates are tunicates and lancelets
– Marine inver tebrates that use their pharyngeal slits for suspension
feeding
• Most chordates are ver tebrates
– With a head and a backbone made of vertebrae
18.16 Lampreys are ver tebrates that lack hinged jaws
• Lampreys lack hinged jaws and paired fins
• Most ver tebrates have hinged jaws
• Which may have evolved from skeletal suppor ts of the gill slits
18.17 Jawed ver tebrates with gills and paired fins include sharks, ray-finned fishes, and
lobe-fins
• Three lineages of jawed ver tebrates with gills and paired fins
– Are commonly called fishes
Chondrichthyans
• Chondrichthyans
– Have a flexible skeleton made of car tilage
– Include sharks and rays
Ray-finned Fishes
• The ray-finned fishes have
– A skeleton reinforced with a hard matrix of calcium phosphate
– Operculi that move water over the gills
– A buoyant swim bladder
Lobe-fins
• The lobe-fin fishes
– Have muscular fins suppor ted by bones
18.18 Amphibians were the first
tetrapods—ver tebrates with two pairs of limbs
• Amphibians
– Were the first tetrapods with limbs allowing movement on land
– Include frogs, toads, salamanders, and caecilians
• Most amphibian embr yos and lar vae
– Still must develop in water
18.19 Reptiles are amniotes—tetrapods with a terrestrially adapted egg
• Terrestrial adaptations of reptiles include
– Waterproof scales
– A shelled, amniotic egg
• Living reptiles other than birds
– Are ectothermic
• Dinosaurs, the most diverse reptiles to inhabit land
– Included some of the largest animals ever to inhabit land
– May have been endothermic, producing their own body heat
18.20 Birds are feathered reptiles with adaptations for flight
• Birds evolved from
– A lineage of small, two-legged dinosaurs called theropods
• Birds are reptiles that have
– Wings, feathers, endothermic metabolism, and many other
adaptations related to flight
• Flight ability is typical of birds
– But there are a few flightless species
18.21 Mammals are amniotes that have hair and produce milk
• Mammals are endothermic amniotes with
– Hair, which insulates their bodies
– Mammary glands, which produce milk
• Monotremes lay eggs
• The embryos of marsupials and eutherians
– Are nur tured by the placenta within the uterus
• Marsupial offspring
– Complete development attached to the mother’s nipple, usually
inside a pouch
• Eutherians, placental mammals
– Complete development before bir th
18.23 Humans threaten animal diversity by introducing non-native species
• Introduced species
– Are threatening Australia’s native animals
Chapter 21: Animal Nutrition
21.1 Animals ingest their food in a variety of ways
• Animal diets are highly varied, and include
– Herbivores, plant-eaters
– Carnivores, meat-eaters
– Omnivores, eating both plants and other animals
• Animal feeding mechanisms include
– Suspension, substrate, fluid, and bulk feeding
21.2 Overview: Food processing occurs in four stages
• In chemical digestion
– Polymers in food are broken down to monomers
21.3 Digestion occurs in specialized compartments
• Food is digested in compartments
– Which house hydrolytic enzymes
• Sponges digest their food
– Entirely in food vacuoles
• In cnidarians and flatworms
– The digestive compartment is a gastrovascular cavity with a single
opening, the mouth
• Most animals have an alimentary canal
– Running from mouth to anus, with specialized regions
21.4 The human digestive system consists of an alimentary canal and accessory glands
• The rhythmic muscle contractions of peristalsis
– Squeeze food toward the stomach along the alimentary canal
• The pyloric sphincter
– Regulates the passage of food from the stomach to the small
intestine
21.5 Digestion begins in the oral cavity
• The teeth break up food, saliva moistens it
– And salivary enzymes begin the hydrolysis of starch
• The tongue pushes the bolus of food into the pharynx
21.6 The food and breathing passages both open into the pharynx
• The swallowing reflex
– Moves food from the pharynx into the esophagus, while keeping it
out of the trachea
21.7 The Heimlich maneuver can save lives
• The Heimlich maneuver
– Can dislodge food from the pharynx or trachea during choking
21.8 The esophagus squeezes food along to the stomach by peristalsis
• Peristalsis in the esophagus
– Moves food into the stomach
21.9 The stomach stores food and breaks it down with acid and enzymes
• Pepsin in the gastric juice
– Begins the hydrolysis of protein
– Mixes with food to produce acid chyme
21.10 Bacterial infections can cause ulcers
•
Bacterial infections in the stomach and duodenum
– Are associated with ulcers
21.11 The small intestine is the major organ of chemical digestion and nutrient absorption
• Alkaline pancreatic juice neutralizes the acid chyme
– And its enzymes digest food polymers
• Bile, made in the liver and stored in the gall bladder
– Emulsifies fat for attack by pancreatic enzymes
• Enzymes from cells of the intestine
– Complete the digestion of many nutrients
• Folds of the intestinal lining, and tiny, fingerlike villi
– Increase the absorptive surface
• Nutrients pass across the epithelium and into the blood
– Which flows to the liver where nutrients are processed and stored
21.12 The large intestine reclaims water and compacts the feces
• The large intestine, or colon
– Reabsorbs water from undigested material
• Feces are stored in the rectum
21.13 Adaptations of vertebrate digestive systems reflect diet
• Dietary adaptations of herbivores include
– Longer alimentary canals
– Cellulose-digesting microbes housed in special chambers
• Alimentary canals of herbivores
– Are usually longer than those found in carnivores
• Ruminants such as cows
– Process food with the aid of microbes in four chambers
21.14 Overview: A healthful diet satisfies three needs
• A healthy diet provides
– Fuel for an organism’s activities
– Raw materials for biosynthesis
– Essential nutrients
21.15 Chemical energy powers the body
• Once nutrients are inside cells
– They can be oxidized by cellular metabolism to generate energy in
the form of ATP
• The basal metabolic rate (BMR)
– Is the energy a resting animal requires each day
• Excess energy
– Is stored as glycogen or fat
• More energy is required for an active life
21.16 An animal’s diet must supply essential nutrients
• Essential nutrients
– Are those that an animal must obtain from its diet
21.17 Vegetarians must be sure to obtain all eight essential amino acids
• The eight essential amino acids can be obtained from animal protein
– Or from the proper combination of plant foods
21.18 A healthy diet includes 13 vitamins
•
Vitamins and minerals
– Are essential in the human diet
• Most of these vitamins function as coenzymes
21.19 Essential minerals are required for many body functions
• Minerals are inorganic nutrients
– That play a variety of roles
21.20 Do you need to take vitamin and mineral supplements?
• Supplements
– Ensure a sufficient quantity of vitamins and nutrients
• Megadoses may be dangerous
21.21 What do food labels tell us?
• Food labels
– Provide important nutritional information
21.22 Obesity is a human health problem
• Adipose (fat) cells produce leptin
– A hormone that influences appetite
• Research on mice
– Has shown that a defect in the gene for leptin may cause obesity
• Obesity in humans
– Is usually caused by lack of exercise and abundance of fattening
foods
– May partly stem from an evolutionary advantage of fat hoarding
21.23 What are the health risks and benefits of fad diets?
• Weight loss diets
– May help individuals lose weight, but may have health risks
21.24 Diet can influence cardiovascular disease and cancer
• A healthy diet
– May reduce the risk of cardiovascular disease and cancer
Chapter 22: Gas Exchange
• The process of gas exchange, often called respiration
– Is the interchange of O2 and CO2 between an organism and its
environment
22.1 Overview: Gas exchange involves breathing, transport of gases, and exchange of
gases with tissue cells
• The three phases of gas exchange
• Gas exchange
• Provides O2 for cellular respiration and removes its waste product,
CO2
22.2 Animals exchange O2 and CO2 across moist body surfaces
• Respiratory surfaces
– Must be thin and moist for diffusion of O2 and CO2 to occur
• Some animals, like the earthworm
– Use their entire skin as a gas-exchange organ
• In most animals
– Specialized body parts provide large respiratory surfaces for gas
exchange
22.3 Gills are adapted for gas exchange in aquatic environments
• Gills are extensions of the body
– That absorb O2 dissolved in water
• In a fish, gas exchange
– Is enhanced by ventilation and the countercurrent flow of water
and blood
22.4 The tracheal system of insects provides direct exchange between the air and body
cells
• Land animals
– Exchange gases by breathing air
• Tracheal systems in insects
– Transport O2 directly to body cells through a network of finely
branched tubes
22.5 Terrestrial vertebrates have lungs
• In mammals, air inhaled through the nostrils
– Passes through the pharynx and larynx into the trachea, bronchi,
and bronchioles
• The bronchioles end in clusters of tiny sacs called alveoli
– Where gas exchange occurs
22.6 Smoking is a deadly assaults on our respiratory system
• Mucus and cilia in the respiratory passages
– Protect the lungs
– Can be destroyed by smoking
• Smoking
– Causes lung cancer, heart disease, and emphysema
22.7 Breathing ventilates the lungs
• Breathing
– Is the alternation of inhalation and exhalation
•
The contraction of rib muscles and the diaphragm
– Expands the chest cavity and reduces air pressure in the alveoli
(negative pressure breathing)
• Vital capacity is the maximum volume of air we can inhale and exhale
– But our lungs still hold a residual volume
• Air flows in one direction
– Through the more efficient lungs of birds
22.9 Breathing is automatically controlled
• Breathing control centers in the brain
– Keep breathing in tune with body needs, sensing and responding to
the CO2 level in the blood
• A drop in blood pH
– Triggers an increase in the rate and depth of breathing
22.9 Blood transports respiratory gases
• The heart pumps oxygen-poor blood to the lungs
– Where it picks up O2 and drops off CO2
• Then the heart pumps the oxygen-rich blood to body cells
– Where it drops off O2 and picks up CO2
• Gases diffuse down partial-pressure gradients
– In the lungs and the tissues
22.10 Hemoglobin carries O2 and helps transport CO2 and buffer the blood
• Hemoglobin in red blood cells
– Transports oxygen, helps buffer the blood and carries some CO2
• Most CO2 in the blood
– Is transported as bicarbonate ions in the plasma
22.11 The human fetus exchanges gases with the mother’s bloodstream
• A human fetus
– Exchanges gases with maternal blood in the placenta
• Fetal hemoglobin
– Enhances oxygen transfer from maternal blood
• At birth, increasing CO2 in the fetal blood
– Stimulates the breathing control centers to initiate breathing
Chapter 23: Circulation
23.1 The circulatory system connects with all body tissues
• In many animals, microscopic blood vessels called capillaries
– Form an intricate network among the tissue
• Capillaries
– Are the sites of exchange between blood and interstitial fluid
23.2 Several types of internal transport have evolved in animals
• In cnidarians and flatworms
– The gastrovascular cavity functions in both digestion and internal
transport
• In the open circulatory systems of arthropods and many molluscs
– A heart pumps blood through open-ended vessels to bathe tissue
cells directly
• In closed circulatory systems
– A heart pumps blood through arteries to capillaries
– Veins return blood to the heart
23.3 Vertebrate cardiovascular systems reflect evolution
• The two-chambered heart of a fish pumps blood in a single circuit
– From gill capillaries to systemic capillaries and back to the heart
• Land vertebrates have double circulation
– With separate pulmonary and systemic circuits
• Amphibians and reptiles
– Have three-chambered hearts
• Birds and mammals
– Have four-chambered hearts
23.4 The human heart and cardiovascular system are typical of mammals
• The mammalian heart
– Has two thin-walled atria that pump blood into the ventricles
– Has thick-walled ventricles that pump blood to all other body
organs
Blood flow through the human cardiovascular system
23.5 The structure of blood vessels fits their functions
• A single layer of epithelial cells
– Forms the walls capillaries
• Arteries and veins
– Have smooth muscle and connective tissue
23.6 The heart contracts and relaxes rhythmically
• During diastole
– Blood flows from the veins into the heart chambers
• During systole
– Contractions of the atria push blood into the ventricles
– Stronger contractions of the ventricles propel blood into the large
arteries
• Cardiac output
– Is the amount of blood/minute pumped into the systemic circuit
• Heart valves
– Prevent the backflow of blood
23.7 The pacemaker sets the tempo of the heartbeat
• The pacemaker (SA node) generates electrical signals
– That trigger contraction of the atria
• The AV node
– Relays these signals to the ventricles
• An electrocardiogram (ECG)
– Records the electrical changes in the heart
• Heart rate
– Adjusts to body needs
23.8 What is a heart attack?
• A heart attack is damage to cardiac muscle
– Usually resulting from a blocked coronary artery
• In atherosclerosis
– Plaques develop in the inner walls of arteries and can block blood
flow
23.9 Blood exerts pressure on vessel walls
• Blood pressure
– Is the force blood exerts on vessel walls
– Depends on cardiac output and the resistance of vessels
• Pressure is highest in the arteries
– And lowest in the veins
• Muscle contractions and one-way valves
– Keep blood moving through the veins to the heart
23.10 Measuring blood pressure can reveal cardiovascular problems
• Blood pressure
– Is measured as systolic and diastolic pressures
• Hypertension
– Is a serious cardiovascular problem
23.11 Smooth muscle controls the distribution of blood
• Constriction of arterioles and precapillary sphincters
– Controls blood flow through capillary beds
23.12 Capillaries allow the transfer of substances through their walls
• The transfer of materials between the blood and interstitial fluid occurs
– By diffusion
– By pressure flow through clefts between epithelial cells
• Blood pressure forces fluid out of the capillary at the arterial end
– And osmotic pressure draws fluid at the venous end
23.13 Blood consists of red and white blood cells suspended in plasma
• Plasma is about 90% water
– And contains various inorganic ions, proteins, nutrients, wastes,
gases, and hormones
• Red blood cells (erythrocytes)
– Transport O2 bound to hemoglobin
• White blood cells (leukocytes)
–
Function both inside and outside the circulatory system to fight
infections and cancer
23.14 Too few or too many red blood cells can be unhealthy
• Anemia
– Is an abnormally low amount of hemoglobin or red blood cells
• The hormone erythropoietin
– Regulates red blood cell production
• Some athletes
– Artificially increase their red blood cell production, a dangerous
practice
23.15 Blood clots plug leaks when blood vessels are injured
• When a blood vessel is damaged
– Platelets help trigger the conversion of fibrinogen to fibrin,
forming a clot that plugs the leak
23.16 Stem cells offer a potential cure for blood cell diseases
• Stem cells divide in bone marrow
– To produce all blood cells
– And may be used to treat some blood disorders
Chapter 24: The Immune System
24.1 Innate defenses against infection include the skin and mucous membranes,
phagocytic cells, and antimicrobial proteins
• Innate immunity
– Is present and effective long before exposure to pathogens
• Microbes that breach the body’s external defenses
– Are engulfed and destroyed by macrophages
• Interferons are proteins produced by virus-infected cells
– That help other cells resist viruses
24.2 The inflammatory response mobilizes nonspecific defense forces
• Tissue damage triggers the inflammatory response
• The inflammatory response
• Can disinfect tissues and limit further infection
24.3 The lymphatic system becomes a crucial battleground during infection
• The lymphatic system
– Is a network of lymphatic vessels and organs
• The vessels collect fluid from body tissues
– And return it as lymph to the blood
• Lymph organs such as the spleen and lymph nodes
– Are packed with white blood cells that fight infections
24.4 The immune response counters specific invaders
• Our immune system
– Responds to foreign molecules called antigens
• The immune system reacts to antigens
– And “remembers” an invader
• We can temporarily acquire passive immunity
– By receiving “premade” antibodies
• Infection or vaccination
– Triggers active immunity
24.5 Lymphocytes mount a dual defense
• Two kinds of lymphocytes carry out the immune response
– B cells secrete antibodies that attack antigens
– T cells attack cells infected with pathogens
• Millions of kinds of B cells and T cells, each with different membrane
receptors
– Wait in the lymphatic system, where they may respond to invaders
24.6 Antigens have specific regions where antibodies bind to them
• Antigenic determinants
– Are the specific regions on an antigen to which antibodies bind
24.7 Clonal selection musters defensive forces against specific antigens
• When an antigen enters the body
– It activates only a small subset of lymphocytes with
complementary receptors
• The selected lymphocyte cells multiply into clones of short-lived effector
cells
–
Specialized for defending against the antigen that triggered the
response
The Steps of Clonal Selection
• In the primary immune response, clonal selection
– Produces effector cells and memory cells that may confer lifelong
immunity
• In the secondary immune response
– Memory cells are activated by a second exposure to the same
antigen, which initiates a faster and more massive response
Primary vs. Secondary Immune Response
• The primary immune response
– Is slower than the secondary immune response
24.8 Antibodies are the weapons of humoral immunity
• Antibody molecules
– Are secreted by plasma (effector) B cells
• An antibody molecule
– Has antigen-binding sites specific to the antigenic determinants
that elicited its secretion
24.9 Antibodies mark antigens for elimination
• Antibodies promote antigen elimination
– Through several mechanisms
24.10 Monoclonal antibodies are powerful tools in the lab and clinic
• Monoclonal antibodies
– Are produced by fusing B cells specific for a single antigenic
determinant with easy to grow tumor cells
• These molecules
– Are useful in research, diagnosis, and treatment of certain cancers
24.11 Helper T cells stimulate humoral and cell-mediated immunity
• Helper T cells and cytotoxic T cells
– Are the main effectors of cell-mediated immunity
• Helper T cells
– Also stimulate the humoral responses
• In cell-mediated immunity, an antigen-presenting cell
– Displays a foreign antigen and one of the body’s own self proteins
to a helper T cell
• The helper T cell’s receptors
– Recognize the self-nonself complexes and the interaction activates
the helper T cells
• The helper T cell
– Can then activate cytotoxic T cells and B cells
24.12 HIV destroys helper T cells, compromising the body’s defenses
• The AIDS virus attacks helper T Cells
– Opening the way for opportunistic infection
24.13 Cytotoxic T cells destroy infected body cells
• Cytotoxic T cells
– Bind to infected body cells and destroy them
24.14 Cytotoxic T cells may help prevent cancer
• Cytotoxic T cells may attack cancer cells
– Which have abnormal surface molecules
24.15 The immune system depends on our molecular fingerprints
• The immune system
– Normally reacts only against nonself substances, not against self
– May reject transplanted organs because these cells lack the unique
“fingerprint” of the recipient’s self proteins
24.16 Malfunction or failure of the immune system causes disease
• In autoimmune diseases
– The system turns against the body’s own molecules
• In immunodeficiency diseases
– Immune components are lacking, and frequent infections recur
• Physical and emotional stress
– May weaken the immune system
24.17 Allergies are overreactions to certain environmental antigens
• Allergies
– Are abnormal sensitivities to antigens (allergens) in the
surroundings
Chapter 10: The molecular Biology of the Gene
10.1 Experiments showed that DNA is the genetic material
• The Hershey-Chase experiment showed that certain viruses reprogram
host cells
– To produce more viruses by injecting their DNA
10.2 DNA and RNA are polymers of nucleotides
• DNA is a nucleic acid
– Made of long chains of nucleotide monomers
• DNA has four kinds of nitrogenous bases
– A, T, C, and G
• RNA is also a nucleic acid
– But has a slightly different sugar
– And has U instead of T
10.3 DNA is a double-stranded helix
• James Watson and Francis Crick
– Worked out the three-dimensional structure of DNA, based on
work by Rosalind Franklin
• The structure of DNA
– Consists of two polynucleotide strands wrapped around each other
in a double helix
• Hydrogen bonds between bases
– Hold the strands together
• Each base pairs with a complementary partner
– A with T, and G with C
10.4 DNA replication depends on specific base pairing
•
DNA replication
– Starts with the separation of DNA strands
• Then enzymes use each strand as a template
– To assemble new nucleotides into complementary strands
• DNA replication is a complex process
– Due in part to the fact that some of the helical DNA molecule must
untwist
10.5 DNA replication: A closer look
• DNA replication
– Begins at specific sites on the double helix
• Each strand of the double helix
– Is oriented in the opposite direction
• Using the enzyme DNA polymerase
– The cell synthesizes one daughter strand as a continuous piece
• The other strand is synthesized as a series of short pieces
– Which are then connected by the enzyme DNA ligase
• 10.6 The DNA genotype is expressed as proteins, which provide the molecular
basis for phenotypic traits
• The information constituting an organism’s genotype
• Is carried in its sequence of its DNA bases
• A particular gene, a linear sequence of many nucleotides
• Specifies a polypeptide
• The DNA of the gene is transcribed into RNA
– Which is translated into the polypeptide
• Studies of inherited metabolic disorders in mold
– First suggested that phenotype is expressed through proteins
10.7 Genetic information written in codons is translated into amino acid sequences
• The “words” of the DNA “language”
– Are triplets of bases called codons
• The codons in a gene
– Specify the amino acid sequence of a polypeptide
10.8 The genetic code is the Rosetta stone of life
• Nearly all organisms
– Use exactly the same genetic code
10.9 Transcription produces genetic messages in the form of RNA
• In the nucleus, the DNA helix unzips
– And RNA nucleotides line up along one strand of the DNA,
following the base pairing rules
• As the single-stranded messenger RNA (mRNA) peels away from the
gene
– The DNA strands rejoin
10.10 Eukaryotic RNA is processed before leaving the nucleus
• Noncoding segments called introns are spliced out
– And a cap and a tail are added to the ends
10.11 Transfer RNA molecules serve as interpreters during translation
• Translation
– Takes place in the cytoplasm
• A ribosome attaches to the mRNA
– And translates its message into a specific polypeptide aided by
transfer RNAs (tRNAs)
• Each tRNA molecule
– Is a folded molecule bearing a base triplet called an anticodon on
one end
• A specific amino acid
– Is attached to the other end
10.12 Ribosomes build polypeptides
• A ribosome consists of two subunits
– Each made up of proteins and a kind of RNA called ribosomal
RNA
• The subunits of a ribosome
– Hold the tRNA and mRNA close together during translation
10.13 An initiation codon marks the start of an mRNA message
• mRNA, a specific tRNA, and the ribosome subunits
– Assemble during initiation
10.14 Elongation adds amino acids to the polypeptide chain until a stop codon terminates
translation
• Once initiation is complete
– Amino acids are added one by one to the first amino acid
• Each addition of an amino acid
– Occurs in a three-step elongation process
• The mRNA moves a codon at a time
– And a tRNA with a complementary anticodon pairs with each
codon, adding its amino acid to the peptide chain
• Elongation continues
– Until a stop codon reaches the ribosome’s A site, terminating
translation
10.15 Review: The flow of genetic information in the cell is DNARNAprotein
• The sequence of codons in DNA, via the sequence of codons
– Spells out the primary structure of a polypeptide
10.16 Mutations can change the meaning of genes
• Mutations are changes in the DNA base sequence
– Caused by errors in DNA replication or recombination, or by
mutagens
• Substituting, inserting, or deleting nucleotides alters a gene
– With varying effects on the organism
10.17 Viral DNA may become part of the host chromosome
• Viruses
– Can be regarded as genes packaged in protein
• When phage DNA enters a lytic cycle inside a bacterium
– It is replicated, transcribed, and translated
• The new viral DNA and protein molecules
– Then assemble into new phages, which burst from the host cell
•
In the lysogenic cycle
– Phage DNA inserts into the host chromosome and is passed on to
generations of daughter cells
• Much later
– It may initiate phage production
10.18 Many viruses cause disease in animals
• Many viruses cause disease
– When they invade animal or plant cells
• Many, such as flu viruses
– Have RNA, rather than DNA, as their genetic material
• Some animal viruses
– Steal a bit of host cell membrane as a protective envelope
– Can remain latent in the host’s body for long periods
10.19 Plant viruses are serious agricultural pests
• Most plant viruses
– Have RNA genomes
– Enter their hosts via wounds in the plant’s outer layers
10.20 Emerging viruses threaten human health
10.21 The AIDS virus makes DNA on an RNA template
• HIV, the AIDS virus
– Is a retrovirus
• Inside a cell, HIV uses its RNA as a template for making DNA
– To insert into a host chromosome
10.22 Bacteria can transfer DNA in three ways
• Bacteria can transfer genes from cell to cell by one of three processes
– Transformation, transduction, or conjugation
• Once new DNA gets into a bacterial cell
– Part of it may then integrate into the recipient’s chromosome
10.23 Bacterial plasmids can serve as carriers for gene transfer
• Plasmids
– Are small circular DNA molecules separate from the bacterial
chromosome
• Plasmids can serve as carriers
– For the transfer of genes