SI Worksheet #1 (Chapter 19,22,23)

BY 123

Meeting 12/1/2015

Chapter 19:

  1. What is the difference between an epidemic and a pandemic?

Anepidemicoccurs when a disease affects a greater number people than is usual for the locality or one that spreads to areas not usually associated with the disease. Apandemicis anepidemicof world-wide proportions.

  1. What are viroids?

An infectious entity affecting plants, smaller than a virus and consisting only of nucleic acid without a protein coat; consisting solely of short strands of circular, single-stranded RNA

  1. What are prions?

Disease-causing form of a normal protein. These mis-folded proteins do not multiply in the host organism that they infect. Instead, they affect the brain structure by acting as a template, inducing proteins with normal folding to convert to the abnormal prion form.

These newly formed mis-folded proteins, in turn, act as further templates for the conversion of more normal proteins, leading to an exponential accumulation of prions in the tissue of the central nervous system. These abnormally folded proteins form plaques which are thought to cause "entanglement" of neurofibrils and interfere with synapse function. The nerve cells are eventually damaged and lost, which causes tiny vacuoles to form in the brain. These give the brain a sponge-like appearance under the microscope, hence the term spongiform disease arose

Chapter 22:

  1. What are the three thing that Darwin was able to explain about life and organisms?

The unity of life, the diversity of life, and how organisms fit their environment

  1. What is a phylogenetic tree?

a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species or other entities

  1. What is homology?

the existence of shared ancestry between a pair ofstructures, or genes, in different species

  1. What are vestigial structures? Give an example.

genetically determinedstructuresor attributes that have apparently lost most or all of their ancestral function in a given species, but have been retained during the process of evolution. The appendix

  1. What is convergent evolution?

the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

  1. What is Pangea?

a hypothetical supercontinent that included all current land masses, believed to have been in existence before the continents broke apart during the Triassic and Jurassic Periods.

Chapter 23:

  1. What is meant by evolution happening in populations and not in individual organisms?

Evolution is a change in the gene pool of a population over time. A gene is a hereditary unit (the microscopic `atom') that can be passed on unaltered for many generations. The gene pool (also called the phenotype of a species) is the set of all genes in a species or population (the macroscopic `object').

  1. What is microevolution?

evolutionary change within a species or small group of organisms, especially over a short period.

  1. What are the three types of microevolution? Describe each.
  1. Gene flow (migration): Some beetles with brown genes immigrated from another population, or some beetles carrying green genes emigrated.
  2. Genetic drift: When the beetles reproduced, just by random luck more brown genes than green genes ended up in the offspring
  3. Natural selection: Beetles with brown genes escaped predation and survived to reproduce more frequently than beetles with green genes, so that more brown genes got into the next generation.
  4. Mutation: Some "green genes" randomly mutated to "brown genes" (although since any particular mutation is rare, this process alone cannot account for a big change in allele frequency over one generation)
  1. Discuss heritable v. non-heritable variation.

Heritable think Mendel’s traits. Non-heritable thinking muscle building

  1. How are new alleles formed?

Mutations introduce new alleles into a population

  1. Why does a mutation in a somatic cell not lead to new allelic formation?

Only mutations in gametes lead to new allelic formation because gametes are what are involved in fertilization and formation of the zygote which turns into the new organism carrying the genes and any mutations.

  1. What is natural selection?

the process whereby organisms better adapted to their environment tend to survive and produce more offspring.

  1. What are the two types of genetic drift? Describe each.
  1. Founder’s effect: the reduced genetic diversity that results when a population is descended from a small number of colonizing ancestors; think people that live on an island, a closed off fixed population that breeds within itself
  2. Bottleneck effect:when a population's size is reduced for at least one generation; think a natural disaster causes a population to suddenly decrease, decreasing the genetic variability in the gene pool
  1. What is gene flow?

the transfer of alleles orgenesfrom one population to another

  1. What are the assumptions of Hardy-Weinberg Equilibrium?

The population size is large.

Random mating is occurring.

No mutation takes place.

No genes are input from other sources (no immigration takes place)

No natural selection occurs.

  1. Hardy-Weinberg Problems:

1. If the frequency of two alleles in a gene pool is 90% A and 10% a, what is the frequency of individuals in the population with the genotype Aa?

0.18

p= 0.9 andq= 0.1. From this, you can calculate the heterozygotes: 2pq= 2 (0.9) (0.1) = 0.18.

2. If a population experiences no migration, is very large, has no mutations, has random mating, and there is no selection, which would you predict?

The makeup of the population's gene pool will remain virtually the same as long as these conditions hold.

3. In a population that is in Hardy-Weinberg equilibrium, the frequency of the homozygous recessive genotype is 0.09. What is the frequency of individuals that are homozygous for the dominant allele?

0.49

q2= 0.09, soq= 0.3.
p= 1 −q, sop= 1 − 0.3 = 0.7
AA=p2= 0.49

4. In humans, Rh-positive individuals have the Rh antigen on their red blood cells, while Rh-negative individuals do not. If the Rh-positive phenotype is produced by a dominant gene (A), and the Rh-negative phenotype is due to its recessive allele (a), what is the frequency of the Rh-positive allele if 84% of a population is Rh-positive?

0.60

q2= 0.16;q= 0.4
p= 1 −q, sop= 0.6 = 60%