Supplemental Instruction 11/9/2017 BIoL 211 Exam 4 review Supplemental Instruction 11/9/2017

4 evolutionary processes Mutations Natural Selection Genetic Drift Gene Flow

Mutations Change in DNA base sequence. The mechanism by which new alleles arise. Most mutations have harmful or neutral effects on the individual. Non-harmful alleles have evolutionary potential, increasing the likelihood that population survives environmental change. A large population of M. tuberculosis bacteria in a patient’s lungs makes him sick. A few of the bacteria cells happen to have a point mutation in the rpoB gene. Drug therapy begins killing most M. tuberculosis. Patient seems cured and so the drug therapy is ended. However, even though the population of these cells is drastically reduced, now most of the remaining cells are resistant to the drug.

Natural selection Occurs in a population when individuals with a favorable heritable phenotype (adaptation) produce more surviving offspring than individuals without this adaptation. Ex. Ground finch Small seeds were abundant before a drought. Birds average beak size was relatively small. After the drought, there were not much small seeds produced. The bird population declined due to starvation, but the birds with deep beaks that feed on large seeds were more likely to survive. Eventually beak depth had increased in the ground finches.

Genetic drift Change in allele frequencies due to chance. Founder effect – results when a new population is formed by a few individuals Genetic bottleneck - results when population size is dramatically reduced The loss of alleles increases extinction risk due to reduced evolutionary potential and increased likelihood of inbreeding depression. American bison were once very prevalent in North America but were hunted close to extinction in the late 1800s. Though the population is recovering, the rapid decrease in population size has led to a population with very little genetic variability.

Gene Flow Occurs when individuals immigrate or emigrate to a new population. The population may gain or lose alleles. Can also be thought of as allele flow. Potential consequences include increased genetic similarities to other population, increased genetic diversity through addition of alleles, or reduced genetic diversity through loss of alleles. Two populations of badgers are separated by a wide river. Originally, all individuals of population 1 had one allele for paw size (allele P.) All individuals of population 2 had a different allele for a different paw size (allele p.) Some badgers from population 1 migrated and swam to the other side of the river to join population 2. Genetic diversity increased among population 2 because the frequency of allele a was no longer 100%.

define Allele: Fitness: Adaptation: Inbreeding depression: Contains instructions for producing heritable phenotype. Number of offspring produced by an individual relative to other members of the population. Increases fitness. Low average fitness in a population due to high frequency of individuals that are homozygous for a harmful (defective) allele.

define Gene: Heredity: Evolution: Speciation: DNA segment containing instructions for producing a heritable trait. Transmission of genetic information from one generation to the next. The change in frequency of alleles in a population over time. Formation of multiple species from 1 ancestral species.

Virus reproduction Lysogeny Virus inserts genome into host genome, and remains dormant (latency) as host cell divides, increasing the number of infected cells. Ex: HIV The virus can activate replicative growth at a later time. Replicative Growth Viral genome uses host cell’s biosynthetic material to produce viral proteins which then bud or lyse from host cell.

Questions How do viruses cause illness? Virus A stores its genetic material as RNA. Virus B stores its genetic material as DNA. Which virus does more damage? Why? When virus uses host cell’s biosynthetic machinery to reproduce, it makes the person weak. The virus damages or destroys the host cells during reproduction. Virus A. Viruses that store their genetic material as RNA have a high mutation rate, which means they have repeatedly evolved resistance to drugs. Ex. Flu and HIV are caused by viruses with RNA-based genomes.

questions What do you know about mitosis? Produces somatic cells. What do you know about meiosis? Produces somatic cells. 2 daughter cells are produced. Each daughter cell is a genetic copy of the parent cell (unless a mutation occurs.) Produces male sperm and female egg gametes in eukaryotes 4 daughter cells are produced Daughter cells have 1/2 as many chromosomes as parent cell Daughter cells are genetically different from parent cell

mitosis Chromosomes replicate and move to the center of the nucleus, the nuclear membrane dissolves, replicated chromosomes separate from each other and are pulled to opposite poles of the cell, cytokinesis occurs.

meiosis Chromosomes replicate, the nuclear membrane dissolves, crossing over occurs, one copy of each homologous chromosomes is pulled to opposite poles of the cell, cytokinesis occurs, replicated chromosomes separate and each copy is pulled to opposite poles of the cell, cytokinesis occurs.

3 ways meiosis contributes to genetic diversity Independent assortment Crossing over Fertilization Occurs when one of each homologous chromosome is randomly pulled to an opposite pole prior to cytokinesis in meiosis. Segments of homologous chromosomes are exchanged during meiosis, which results in linked genes being distributed to different gametes. Joining of male sperm cell and female egg cell.

Good luck on test! Covers Viruses, Meiosis and Mitosis, Heredity, and Evolution. 45 MC questions Open from Monday (11/13) to Friday (11/17) No Exam Review for non-cumulative final. Answer Key Policy