BIOL 1107 Learning

Introduction (Ch. 1)

Required

  1. What are the characteristics of life? There are 5 unifying themes of life:

    • Organization

      • The hierarchy of life unfolds as follows: biosphere > ecosystem > community > population > organism > organ system > organ > tissue > cell > organelle > molecule > atom. With each step up, new properties emerge (emergent properties) as a result of interactions among components at the lower levels.

      • Structure and function are correlated at all levels of biological organization. The cell is the lowest level that can perform all activities required for life. Cells are either prokaryotic or eukaryotic. Eukaryotic cells have a DNA-containing nucleus and other membrane-enclosed organelles. Prokaryotic cells lack such organelles.

    • Information

      • Genetic information is encoded in the nucleotide sequences of DNA. It is DNA that transmits heritable information from parents to offspring. DNA sequences (called genes) program a cell’s protein production by being transcribed into mRNA and then translated into specific proteins, a process called gene expression. Gene expression also produces RNAs that are not translated into proteins but serve other important functions.

    • Energy and Matter

      • Energy flows through an ecosystem. Producers convert energy from sunlight to chemical energy, which is used by organisms to do work and is eventually lost from the ecosystem as heat. Chemicals cycle between organisms and the environment.

    • Interactions

      • Organisms interact continuously with physical factors. Plants take up nutrients from the soil and chemicals from the air and use energy from the sun. Interactions among plants, animals, and other organisms affect the participants in varying ways.

    • Evolution

      • Evolution, the process of change that has transformed life on Earth, accounts for the unity and diversity of life. It also explains evolutionary adaptation—the match of organisms to their environments.

      • Biologists classify species according to a system of broader and broader groups. Domain Bacteria and domain Archaea consist of prokaryotes. Domain Eukarya, the eukaryotes, includes various groups of protists as well as plants, fungi, and animals.

      • Darwin proposed natural selection as the mechanism for evolutionary adaptation of populations to their environments. Natural selection is the evolutionary process that occurs when a population is exposed to environmental factors that consistently cause individuals with certain heritable traits to have greater reproductive success than do individuals with other heritable traits.

      • Each species is one twig of a branching tree of life extending back in time through more and more remote ancestral species. All of life is connected through its long evolutionary history.

  2. Scientific inquiry/forming and testing hypotheses

    • In scientific inquiry, scientists make observations (collect data) and use inductive reasoning to draw a general conclusion, which can be developed into a testable hypothesis. Deductive reasoning makes predictions that can be used to test hypotheses.

    • Controlled experiments are designed to demonstrate the effect of one variable by testing control groups and experimental groups differing in only that one variable.

    • A scientific theory is broad in scope, generates new hypotheses, and is supported by a large body of evidence.

    • Observations and experiments must be repeatable, and hypotheses must be testable. Technology is a method or device that applies scientific knowledge for some specific purpose that affects society as well as for scientific research. Diversity among scientists promotes progress in science.

Optional

None

Unit 1: Chemistry and Cells

The Chemical Context of Life (Ch. 2)

Required

  1. Elements cannot be broken down chemically to other substances. A compound contains two or more different elements in a fixed ratio. Oxygen, carbon, hydrogen, and nitrogen make up approximately 96% of living matter.

  2. An atom, the smallest unit of an element, has the following components: protons, neutrons, electrons

  3. An electrically neutral atom has equal numbers of electrons and protons; the number of protons determines the atomic number.

  4. In an atom, electrons occupy specific electron shells; the electrons in a shell have a characteristic energy level. Electron distribution in shells determines the chemical behavior of an atom. An atom that has an incomplete outer shell, the valence shell, is reactive.

  5. Chemical bonds form when atoms interact and complete their valence shells. Covalent bonds form when pairs of electrons are shared. Also single bond and double bond.

  6. Molecules consist of two or more covalently bonded atoms. The attraction of an atom for the electrons of a covalent bond is its electronegativity. Electrons of a polar covalent bond are pulled closer to the more electronegative atom, such as the oxygen in H2O.

  7. An ion forms when an atom or molecule gains or loses an electron and becomes charged. An ionic bond is the attraction between two oppositely charged ions, such as Na+ and Cl-.

  8. Chemical reactions change reactants into products while conserving matter. All chemical reactions are theoretically reversible. Chemical equilibrium is reached when the forward and reverse reaction rates are equal.

  9. Weak interactions reinforce the shapes of large molecules and help molecules adhere to each other. A hydrogen bond is an attraction between a hydrogen atom carrying a partial positive charge and an electronegative atom carrying a partial negative charge.

  10. Molecular shape is usually the basis for the recognition of one biological molecule by another.

  11. Chemical reactions change reactants into products while conserving matter. All chemical reactions are theoretically reversible. Chemical equilibrium is reached when the forward and reverse reaction rates are equal.

  12. A hydrogen bond forms when a partially negatively charged region on the oxygen of one water molecule is attracted to the partially positively charged hydrogen of a nearby water molecule. Hydrogen bonding between water molecules is the basis for water’s properties.

    • Hydrogen bonding keeps water molecules close to each other, giving water cohesion. Hydrogen bonding is also responsible for water’s surface tension.

    • Water has a high specific heat: Heat is absorbed when hydrogen bonds break and is released when hydrogen bonds form. This helps keep temperatures relatively steady, within limits that permit life. Evaporative cooling is based on water’s high heat of vaporization. The evaporative loss of the most energetic water molecules cools a surface.

    • Ice floats because it is less dense than liquid water. This property allows life to exist under the frozen surfaces of lakes and seas.

    • Water is an unusually versatile solvent because its polar molecules are attracted to ions and polar substances that can form hydrogen bonds. Hydrophilic substances have an affinity for water; hydrophobic substances do not.

  • A water molecule can transfer an H+ to another water molecule to form H3O+ (represented simply by H+ and OH-). Acids donate H+ in aqueous solutions, while Bases donate OH- or accept H+ in aqueous solutions. The concentration of H+ is expressed as pH.

Carbon and the Molecular Diversity of Life (Ch. 3)

Required

  1. Carbon, with a valence of 4, can bond to various other atoms, including O, H, and N. Carbon can also bond to other carbon atoms, forming the carbon skeletons of organic compounds. These skeletons vary in length and shape. Hydrocarbons consist of carbon and hydrogen.

  2. Chemical groups attached to the carbon skeletons of organic molecules participate in chemical reactions (functional groups) or contribute to function by affecting molecular shape.

  3. ATP (adenosine triphosphate) can react with water or other molecules, resulting in the release of energy that can be used by the cell.

  4. Large carbohydrates (polysaccharides), proteins, and nucleic acids are polymers, chains of monomers. Components of lipids vary. Many monomers form larger molecules by dehydration reactions, in which water molecules are released. Polymers can disassemble by the reverse process, hydrolysis. An immense variety of polymers can be built from a small set of monomers.

    1. Carbohydrates serve as fuel and building material

    2. Lipids are a diverse group of hydrophobic molecules

    3. Proteins include a diversity of structures, resulting in a wide range of functions

    4. Nucleic acids store, transmit, and help express hereditary information

A Tour of the Cell (Ch. 4)

Required

  1. Improvements in microscopy that affect the parameters of magnification, resolution, and contrast have catalyzed progress in the study of cell structure. Light microscopy (LM) and electron microscopy (EM), as well as other types, remain important tools.

  2. All cells are bounded by a plasma membrane.

  3. Prokaryotic cells lack nuclei and other membrane-enclosed organelles, while eukaryotic cells have internal membranes that compartmentalize cellular functions.

  4. Plant and animal cells have most of the same organelles: a nucleus, endoplasmic reticulum, Golgi apparatus, and mitochondria. Chloroplasts are present only in cells of photosynthetic eukaryotes.

  5. The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by ribosomes.

  6. The endomembrane system regulates protein traffic and performs metabolic functions.

  7. Mitochondria and chloroplasts change energy from one form to another.

  8. The cytoskeleton functions in structural support for the cell and in motility and signal transmission.

  9. Microtubules shape the cell, guide organelle movement, and separate chromosomes in dividing cells. Microfilaments are thin rods that function in muscle contraction, amoeboid movement, cytoplasmic streaming, and support of microvilli. Intermediate filaments support cell shape and fix organelles in place.

  10. Plant cell walls are made of cellulose fibers embedded in other polysaccharides and proteins.

  11. Cell junctions connect neighboring cells in plants and animals. Plants have plasmodesmata that pass through adjoining cell walls. Animal cells have tight junctions, desmosomes, and gap junctions.

  12. Many components work together in a functioning cell.

Membrane Transport and Cell Signaling (Ch. 5)

Required

  1. In the fluid mosaic model, amphipathic proteins are embedded in the phospholipid bilayer.

  2. Phospholipids and some proteins move sideways within the membrane. The unsaturated hydrocarbon tails of some phospholipids keep membranes fluid at lower temperatures, while cholesterol helps membranes resist changes in fluidity caused by temperature changes.

  3. Membrane proteins function in transport, enzymatic activity, attachment to the cytoskeleton and extracellular matrix, cell-cell recognition, intercellular joining, and signal transduction.

  4. A cell must exchange molecules and ions with its surroundings, a process controlled by the selective permeability of the plasma membrane. Hydrophobic molecules are soluble in lipids and pass through membranes rapidly, whereas polar molecules and ions usually need specific transport proteins.

  5. Diffusion is the spontaneous movement of a substance down its concentration gradient. Water diffuses out of a cell (osmosis) if the solution outside has a higher solute concentration (hypertonic); water enters if the solution has a lower solute concentration (hypotonic). If the concentrations are equal (isotonic), no net osmosis occurs.

  6. In facilitated diffusion, a transport protein speeds water or solute movement down its concentration gradient across a membrane. Ion channels facilitate the diffusion of ions across a membrane. Carrier proteins can undergo changes in shape that translocate bound solutes across the membrane.

  7. Specific membrane proteins use energy, usually in the form of ATP, to do the work of active transport.

  8. Ions can have both a concentration (chemical) gradient and an electrical gradient (voltage). These gradients combine in the electrochemical gradient, which determines the net direction of ionic diffusion.

  9. Cotransport of two solutes occurs when a membrane protein enables the “downhill” diffusion of one solute to drive the “uphill” transport of the other.

  10. Three main types of endocytosis are phagocytosis, pinocytosis, and receptor-mediated endocytosis.

Introduction to Metabolism (Ch. 6)

Required

  1. Metabolism is the collection of chemical reactions that occur in an organism. Enzymes catalyze reactions in intersecting metabolic pathways, which may be catabolic (breaking down molecules, releasing energy) or anabolic (building molecules, consuming energy). Bioenergetics is the study of the flow of energy through living organisms.

  2. Energy is the capacity to cause change; some forms of energy do work by moving matter. Kinetic energy is associated with motion and includes thermal energy, associated with the random motion of atoms or molecules. Heat is thermal energy in transfer from one object to another. Potential energy is related to the location or structure of matter and includes chemical energy possessed by a molecule due to its structure.

  3. A living system’s free energy is energy that can do work under cellular conditions. Organisms live at the expense of free energy. The change in free energy (ΔG) during a biological process tells us if the process is spontaneous. In an exergonic (spontaneous) chemical reaction, the products have less free energy than the reactants (-ΔG). Endergonic (nonspontaneous) reactions require an input of energy (+ΔG). The addition of starting materials and the removal of end products prevent metabolism from reaching equilibrium.

  4. ATP is the cell’s energy shuttle. Hydrolysis of its terminal phosphate yields ADP and Pi and releases free energy.

  5. Through energy coupling, the exergonic process of ATP hydrolysis drives endergonic reactions by transfer of a phosphate group to specific reactants, forming a phosphorylated intermediate that is more reactive. Catabolic pathways drive regeneration of ATP from ADP + Pi.

  6. In a chemical reaction, the energy necessary to break the bonds of the reactants is the activation energy. Enzymes lower the activation energy barrier.

  7. Each type of enzyme has a unique active site that binds one or more substrate(s), the reactant(s) on which it acts. It then changes shape, binding the substrate(s) more tightly (induced fit).

  8. The active site can lower activation energy barrier by orienting substrates correctly, straining their bonds, providing a favorable microenvironment, or even covalently bonding with the substrate.

  9. Each enzyme has optimal conditions (temperature and pH).

Cellular Respiration and Fermentation (Ch. 7)

Required

  1. Cells break down glucose and other organic fuels to yield chemical energy in the form of ATP. Cellular respiration is a more complete breakdown of glucose. In aerobic respiration, oxygen is used as a reactant; in anaerobic respiration, other substances are used in place of oxygen.

  2. The cell taps the energy stored in food molecules through redox reactions, in which one substance partially or totally shifts electrons to another. Oxidation is the loss of electrons from one substance, while reduction is the addition of electrons to the other.

  3. During aerobic respiration, glucose is oxidized to CO2, and O2 is reduced to H2O. Electrons lose potential energy during their transfer from glucose or other organic compounds to oxygen. Electrons are usually passed first to NAD+, reducing it to NADH, and then from NADH to an electron transport chain, which conducts them to O2 in energy-releasing steps. The energy is used to make ATP.

  4. Aerobic respiration occurs in three stages: (1) glycolysis, (2) pyruvate oxidation and the citric acid cycle, and (3) oxidative phosphorylation (electron transport and chemiosmosis).

  5. Glycolysis (“splitting of sugar”) is a series of reactions that breaks down glucose into two pyruvate molecules, which may go on to enter the citric acid cycle, and nets 2 ATP and 2 NADH per glucose molecule.

  6. In eukaryotic cells, pyruvate enters the mitochondrion and is oxidized to acetyl CoA, which is further oxidized in the citric acid cycle.

  7. NADH and FADH2 transfer electrons to the electron transport chain. Electrons move down the chain, losing energy in several energy-releasing steps. Finally, electrons are passed to O2, reducing it to H2O.

  8. Along the electron transport chain, electron transfer causes protein complexes to move H+ from the mitochondrial matrix (in eukaryotes) to the intermembrane space, storing energy as a proton-motive force (H+ gradient). As H+ diffuses back into the matrix through ATP synthase, its passage drives the phosphorylation of ADP, an energy-coupling mechanism called chemiosmosis.

  9. About 34% of the energy stored in a glucose molecule is transferred to ATP during cellular respiration, producing a maximum of about 32 ATP.

  10. Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration. Many carbohydrates can enter glycolysis, most often after conversion to glucose. Amino acids of proteins must be deaminated before being oxidized. The fatty acids of fats undergo beta oxidation to two-carbon fragments and then enter the citric acid cycle as acetyl CoA. Anabolic pathways can use small molecules from food directly or build other substances using intermediates of glycolysis or the citric acid cycle.

Photosynthesis (Ch. 8)

Required

  1. In eukaryotes that are autotrophs, photosynthesis occurs in chloroplasts, organelles containing thylakoids. Stacks of thylakoids form grana.

  2. Photosynthesis is summarized as 6 CO2 + 12 H2O + light energy 🡪 C6H12O6 + 6 O2 + 6 H2O

  3. Chloroplasts split water into hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules. Photosynthesis is a redox process: H2O is oxidized, and CO2 is reduced.

  4. The light reactions in the thylakoid membranes split water, releasing O2, producing ATP, and forming NADPH. The Calvin cycle in the stroma forms sugars from CO2, using ATP for energy and NADPH for reducing power.

  5. Light is a form of electromagnetic energy. The colors we see as visible light include those wavelengths that drive photosynthesis. A pigment absorbs light of specific wavelengths; chlorophyll a is the main photosynthetic pigment in plants. Other accessory pigments absorb different wavelengths of light and pass the energy on to chlorophyll a.

  6. A pigment goes from a ground state to an excited state when a photon of light boosts one of the pigment’s electrons to a higher-energy electron shell. Electrons from isolated pigments tend to fall back to the ground state, giving off heat and/or light.

  7. A photosystem is composed of a reaction-center complex surrounded by light-harvesting complexes that funnel the energy of photons to the reaction-center complex. When a special pair of reaction-center chlorophyll a molecules absorbs energy, one of its electrons is boosted to a higher energy level and transferred to the primary electron acceptor. Photosystem II contains P680 chlorophyll a molecules in the reaction center complex; photosystem I contains P700 molecules.

  8. Linear electron flow during the light reactions uses both photosystems and produces NADPH, ATP, and oxygen.

  9. During chemiosmosis in both mitochondria and chloroplasts, electron transport chains generate an H+ gradient across a membrane. ATP synthase uses this proton-motive force to synthesize ATP.

  10. The Calvin cycle occurs in the stroma, using electrons from NADPH and energy from ATP. One molecule of G3P exits the cycle per three CO2 molecules fixed and is converted to glucose and other organic molecules.

  11. Organic compounds produced by photosynthesis provide the energy and building material for Earth’s ecosystems.

The Molecular Basis of Inheritance (Ch. 13)

Required

  1. DNA is the genetic material. Experiments with bacteria and phages provided the first strong evidence that the genetic material is DNA.

  2. Watson and Crick deduced that DNA is a double helix and built a structural model. Two antiparallel sugar-phosphate chains wind around the outside of the molecule; the nitrogenous bases project into the interior, where they hydrogen-bond in specific pairs: A with T, G with C.

  3. Many proteins work together in DNA replication and repair, including DNA polymerase, primase, and helicase (process of replication).

  4. The Meselson-Stahl experiment showed that DNA replication is semiconservative: The parental molecule unwinds, and each strand then serves as a template for the synthesis of a new strand according to base-pairing rules.

  5. A chromosome consists of a DNA molecule packed together with proteins

The Cell Cycle (Ch. 9)

Required

  1. The genetic material (DNA) of a cell—its genome—is partitioned among chromosomes. Each eukaryotic chromosome consists of one DNA molecule associated with many proteins. Together, the complex of DNA and associated proteins is called chromatin. The chromatin of a chromosome exists in different states of condensation at different times. In animals, gametes have one set of chromosomes, and somatic cells have two sets.

  2. Cells replicate their genetic material before they divide, each daughter cell receiving a copy of the DNA. Prior to cell division, chromosomes are duplicated. Each one then consists of two identical sister chromatids joined along their lengths by sister chromatid cohesion and held most tightly together at a constricted region at the centromeres. When this cohesion is broken, the chromatids separate during cell division, becoming the chromosomes of the daughter cells. Eukaryotic cell division consists of mitosis (division of the nucleus) and cytokinesis (division of the cytoplasm).

  3. Between divisions, a cell is in interphase: the G1, S, and G2 phases. The cell grows throughout interphase, with DNA being replicated only during the synthesis (S) phase. Mitosis and

Cytokinesis make up the mitotic (M) phase of the cell cycle. The mitotic spindle, made up of microtubules, controls chromosome movement during mitosis. In animal cells, it arises from the

  1. centrosomes and includes spindle microtubules and asters. Some spindle microtubules attach to the kinetochores of chromosomes and move the chromosomes to the metaphase plate. After sister chromatids separate, motor proteins move them along kinetochore microtubules toward opposite ends of the cell. The cell elongates when motor proteins push nonkinetochore microtubules from opposite poles away from each other.

  2. Mitosis is usually followed by cytokinesis. Animal cells carry out cytokinesis by cleavage, and plant cells form a cell plate.

  3. During binary fission in bacteria, the chromosome replicates and the daughter chromosomes actively move apart. Some of the proteins involved in bacterial binary fission are related to eukaryotic actin and tubulin. Since prokaryotes preceded eukaryotes by more than a billion years, it is likely that mitosis evolved from prokaryotic cell division.

Unit 2: Genetics

Meiosis and Sexual Life Cycles (Ch. 10)

Required

  1. Offspring acquire genes from parents by inheriting chromosomes. Each gene in an organism’s DNA exists at a specific locus on a certain chromosome.

  2. In asexual reproduction, a single parent produces genetically identical offspring by mitosis. Sexual reproduction combines genes from two parents, leading to genetically diverse offspring.

  3. Normal human somatic cells are diploid. They have 46 chromosomes made up of two sets of 23 chromosomes, one set from each parent. Human diploid cells have 22 homologous pairs of homologs that are autosomes and one pair of sex chromosomes; the latter helps determine whether the person is female (XX) or male (XY).

  4. In humans, ovaries and testes produce haploid gametes by meiosis, each gamete containing a single set of 23 chromosomes (n=23). During fertilization, an egg and sperm unite, forming a diploid (n=46) single-celled zygote, which develops into a multicellular organism by mitosis.

  5. Sexual life cycles differ in the timing of meiosis relative to fertilization and in the point(s) of the cycle at which a multicellular organism is produced by mitosis.

  6. Meiosis I and meiosis II produce four haploid daughter cells. The number of chromosome sets is reduced from two (diploid) to one (haploid) during meiosis I.

  7. Meiosis is distinguished from mitosis by three events of meiosis I, prophase I, metaphase I, and anaphase I.

  8. Meiosis II separates the sister chromatids.

  9. Sister chromatid cohesion and crossing over allow chiasmata to hold homologs together until anaphase I. Cohesins are cleaved along the arms at anaphase I, allowing homologs to separate, and at the centromeres in anaphase II, releasing sister chromatids.

  10. Three events in sexual reproduction contribute to genetic variation in a population: independent assortment of chromosomes during meiosis I, crossing over during meiosis I, and random fertilization of egg cells by sperm. During crossing over, DNA of nonsister chromatids in a homologous pair is broken and rejoined.

  11. Genetic variation is the raw material for evolution by natural selection. Mutations are the original source of this variation; recombination of variant genes generates additional diversity.

Optional

  1. None

Gene Expression: From Gene to Protein (Ch. 14)

Required

  1. Genes specify proteins via transcription and translation.

  2. During gene expression, the information encoded in genes is used to make specific polypeptide chains (enzymes and other proteins) or RNA molecules.

  3. Transcription is the synthesis of RNA complementary to a template strand of DNA. Translation is the synthesis of a polypeptide whose amino acid sequence is specified by the nucleotide sequence in messenger RNA (mRNA).

  4. Genetic information is encoded as a sequence of nonoverlapping nucleotide triplets, or codons. A codon in mRNA either is translated into an amino acid (61 of the 64 codons) or serves as a stop signal (3 codons). Codons must be read in the correct reading frame.

  5. RNA synthesis is catalyzed by RNA polymerase, which links together RNA nucleotides complementary to a DNA template strand. Transcription follows the same base-pairing rules as DNA replication, except that in RNA, uracil (U) substitutes for thymine (T).

  6. The three stages of transcription are initiation, elongation, and termination. A promoter, often including a TATA box in eukaryotes, establishes where RNA synthesis is initiated. Transcription factors help eukaryotic RNA polymerase recognize promoter sequences, forming a transcription initiation complex. Termination differs in bacteria and eukaryotes.

  7. Eukaryotic cells modify RNA after transcription. Eukaryotic pre-mRNAs undergo RNA processing, which includes RNA splicing, the addition of a modified nucleotide 5′ cap to the 5′ end, and the addition of a poly-A tail to the 3′ end. The processed mRNA includes an untranslated region (5′ UTR or 3′ UTR) at each end of the coding segment.

  8. Most eukaryotic genes are split into segments: They have introns interspersed among the exons (regions included in the mRNA). In RNA splicing, introns are removed and exons joined. RNA splicing is typically carried out by spliceosomes, but in some cases, RNA alone catalyzes its own splicing. The properties of RNA allow some RNAs (called ribozymes) to act as catalysts. The presence of introns allows for alternative RNA splicing.

  9. Translation. A cell translates an mRNA message into protein using transfer RNAs (tRNAs). After being bound to a specific amino acid by an aminoacyl-tRNA synthetase, a tRNA lines up via its anticodon at the complementary codon on mRNA. A ribosome, made up of ribosomal RNAs (rRNAs) and proteins, facilitates this coupling with binding sites for mRNA and tRNA.

  10. Ribosomes coordinate the three stages of translation: initiation, elongation, and termination. The formation of peptide bonds between amino acids is catalyzed by rRNAs as tRNAs move through the A and P sites and exit through the E site.

  11. Small-scale mutations include point mutations, changes in one DNA nucleotide pair, which may lead to production of nonfunctional proteins. Nucleotide-pair substitutions can cause missense or nonsense mutations. Nucleotide-pair insertions or deletions may produce frameshift mutations.

Mendel and the Gene Idea (Ch. 11)

Required

  1. Gregor Mendel formulated a theory of inheritance based on experiments with garden peas, proposing that parents pass on to their offspring discrete genes that retain their identity through generations. This theory includes two “laws.”

  2. Many genetic disorders are inherited as simple dominant or recessive traits. Most affected (homozygous recessive) individuals are children of phenotypically normal, heterozygous carriers.

  3. The sickle-cell allele has probably persisted for evolutionary reasons: Homozygotes have sickle-cell disease, but heterozygotes have an advantage because one copy of the sickle-cell allele reduces both the frequency and severity of malaria attacks.

The Chromosomal Basis of Inheritance (Ch. 12)

Required

  1. Sex-linked genes exhibit unique patterns of inheritance. Sex is often chromosomally based. Humans and other mammals have an X-Y system in which sex is largely determined by whether a Y chromosome is present.

  2. The sex chromosomes carry sex-linked genes, virtually all of which are on the X chromosome (X-linked). Any male who inherits a recessive X-linked allele (from his mother) will express the trait, such as color blindness.

  3. Aneuploidy, an abnormal chromosome number, results from nondisjunction during meiosis. When a normal gamete unites with one containing two copies or no copies of a particular chromosome, the resulting zygote and its descendant cells either have one extra copy of that chromosome (trisomy, 2n+1) or are missing a copy (monosomy, 2n-1). Polyploidy (extra sets of chromosomes) can result from nondisjunction of all chromosomes.

Genomes and their Evolution (Ch. 18)

Required

  1. Genomes of bacteria, archaea, and eukarya vary in size, number of genes, and gene density.

  2. Duplication, rearrangement, and mutation of DNA contribute to genome evolution. Errors in cell division can lead to extra copies of all or part of entire chromosome sets, which may then diverge if one set accumulates sequence changes. Polyploidy occurs more often in plants than animals and contributes to speciation.

  3. Comparing genome sequences provides clues to evolution and development. Comparisons of genomes from widely divergent and closely related species provide valuable information about ancient and more recent evolutionary history, respectively. Analysis of single nucleotide polymorphisms (SNPs) and copy-number variants (CNVs) within a species can also shed light on the evolution of that species.

Viruses (Ch. 17)

Required

  1. A virus consists of a nucleic acid surrounded by a protein coat. A virus is a small nucleic acid genome enclosed in a protein capsid and sometimes a membranous viral envelope containing viral proteins that help the virus enter a cell. Viruses replicate only in host cells.

  2. Phages (viruses that infect bacteria) can replicate by two alternative mechanisms: the lytic cycle, resulting in the lysis (and death) of the host cell and the release of new phages, and the lysogenic cycle, in which the host cell survives and the bacterial genome is incorporated into the host chromosome and replicated with it.