Chapter 23 (2)

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DesLee26
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Chapter 23 (2)
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2011-03-07 21:11:56
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Section Two
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AP Biology
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  1. The individuals in a pop must differ genetically for evolution to occur. But the presence of __ does not guarantee that a population will evolve.
    genetic variation
  2. A __ is a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring. Different __ of a single species may be isolated geographically from one another, thus exchanging genetic material only rarely. Such isolation is common for island or lake species. But not all populations are isolated,nor must populatins have sharp boundaries.
    • population
    • populations
  3. Still, members of a _- typically breed with one another and thus on average are more closely related to each other than to members of other populations.
    population
  4. We can characterize a populatin's genetic makeup by describing its __, which consists of all the alleles for all the loci in all individuals of the population. If only one allele exists for a particular locus in a population, that allele is said to be __ in the __, and all individuals are homozygous for that allele. But if there are two or more alleles for a particular locus in a __, individuals may be either homo- or heterozygoes.
    • gene pool
    • fixed
    • gene pool
    • population
  5. Each allele has a __ in the population.
    - When studying a locus with two alleles, the convention is to use __ to represent the frequency of one allele and __ to represent the frequency of the other allele.
    • frequency (proportion)
    • p
    • q
  6. One way to assess whether __ or other factors are causing evolution at a particular locus is to determine what the genetic makeup of a population would be if it were not evolving at that locus. We can then compare that scenario with data from a real population. If there are no differences, we can conclude that the real population is not evolving. If there are differences, we can conclude that the real population is evolving- and then we can figure out why.
    natural selection
  7. The __ of a population that is not evolving can be described by the ___, derived in 1908. This principle states that the __ of alleles and genotypes in a population will remain constant from generation to generation, provided that only __ and __ are at work. Such a gene pool is said to be in __.
    • gene pool
    • Hardy- Weinberg principle
    • frequencies
    • Mendelian segregation
    • recombination of alleles
    • Hardy- Weinberg equilibrium
  8. By viewing reproduction as a random selection of alleles from the bin (the __), we are in effect assuming that mating occurs at random- that is, that all male-female matings are equally likely.
    gene pool
  9. The genotype frequencies in the next generation must add up to __. Thus, the equation for __ states that at a locus with two alleles, the three genotypes will appear in the following proportions.
    Equation:___
    • 1 (100%)
    • Hardy- Weinberg equilibrium
    • p2 +2pq+ q2
  10. For a locus with two alleles, only __ genotypes are possible. As a result, the sum of the frequencies of the thre genotypes must equal __ in any population- regardless of whether the population is in __.
    • three
    • 1 (100%)
    • Hardy- Weinberg equilibrium
  11. A population is in __ only if the genotype frequenes are such that the actual frequency of one homozygote is __, the other homozygote is __, and the heterozyogotes is __.
    o Finally, if a population is in __ and its members continue to mate randomly generation after generation, allele and genotype frequencies will remain constant.
    • Hardy-Weinberg equilibrium
    • p2
    • q2
    • 2pq
    • Hardy-Weinberg equilibrium
  12. the __ describes a hypothetical population that is not evolving. But in real populations, the allele and genotype frequencies often do change over time. Such changes can occur when at least one of five conditions of Hardy- Weiberg equilibrium is not met.
    Hardy- Weinberg principle
  13. What are the five conditions of Hardy-Weinberg equilibrium?
    1- __ by altering alleles or (in large scale changes) deleting or duplicaitng entire genes, these modify the gene pool
    2- __ if individuals mate preferentially within a subset of the population, such as their close relatives (inbreeding), random mixing of gametes does not occur, and genotype frequencies change.
    3- __ differences in hthe survival and reproductive success of individuals carrying diffferent genotypes can alter allele frequencines
    4- __ the smaller the pop, the more likely it is that allele frequencies will fluctuate by chance from one generation to the next (genetic drift)
    5- __ by moving alleles into or out of populations, gene flow can alter allele frequencies
    • 1. no mutations
    • 2. random mating
    • 3. no natural selection
    • 4. extremely large population size
    • 5. no gene flow
  14. Departure from any of these conditions usually results in evolutionary change, which, is common in natural populations. It is also common for natural populations to be in __ for specific genes. This apparent contradiction occurs because a population can be evolving at some loci, yet simultaneously be in __ at other loci. In addition, some populations evolve so slowly that changes in their allele and __ are difficult to distinguish from gthose predicted for a nonevolving population.
    • Hardy- Weinberg equilibrium x2
    • genotype frequencies
  15. The __ i often used to test whether evolution is occurring in a population. It also has medical applications. (PKU ex.- p. 474-75)
    The assumption of __ yields an approximation; the real number of carriers may differ. Still our calculations suggest that harmful recessive alleles at this and other loci can be concealed in a population because they are carried by healthy heterozygotes.
    • Hardy-Weinberg equation
    • Hardy-Weinberg equilibrium

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