Chapter 4: Genetics in Wildlife

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Chapter 4 Genetics in Wildlife

• February 13, 2007

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Some basics of genetics

• (1) are segments of hereditary material that are
  positioned on chromosomes within cells
• Chromosomes, which consist of strands of DNA, are
  structures that carry genes are found in the
  nuclei of cells

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Some basics of genetics

• Most cells in our body carry two of each
  chromosome 1 came from our mother, 1 from our
  father
• Humans have a total of 46 chromosomes, or 23
  pairs (23 x 2 46). One set of 23 came from
  mother the other set came from father

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This is a karyotype basically a map of ones
chromosomes
Once again, notice that we get 2 copies of each
chromosome one from each parent
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Gametes

• (2) are otherwise known as sperm and egg cells
• Gametes carry only ONE copy of each chromosome
  (rather than TWO copies like other cells). That
  way, when a sperm and an egg combine, they bring
  to the embryo the two copies of chromosomes one
  from each parent

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Review

• To review thus far
• 1. Chromosomes are strands of DNA that carry
  genes
• 2. Genes are segments of hereditary material
• 3. We inherit one set of chromosomes from each of
  our parents
• 4. Gametes carry just one copy of each chromosome

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Alleles

• Alleles are (3) of genes
• Example We all carry the gene for eye color
  however, some of us carry the blue eye allele, or
  the brown eye allele, etc.
• It is incorrect to say you carry the gene for
  blue eyes rather, you carry the allele for blue
  eyes

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Alleles

• Some alleles are (4) over others and will be
  expressed by the individual who carries them
  (e.g., brown hair)
• Some alleles are (5) to others and will be masked
  and not expressed by the individual who carries
  them (e.g., someone could be a carrier for
  hemophilia)

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What are species?

• Lets set aside discussion of alleles for now
• A species is a naturally occurring group of
  organisms that can successfully (6) and produce
  (7) offspring

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Speciation

• Populations of species can have their gene pools
  segregated by isolating mechanisms
• Such isolation can ultimately lead to (8), which
  is the process of species formation

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Isolating mechanisms

• 1. Pre-mating isolating mechanisms
• Sexual/behavioral differences, physiological
  differences, anatomical differences, mating
  time differences
• 2. Post-mating isolating mechanisms
• Natural developmental abortion hybrid sterility

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All of this discussion leads to

• Natural Selection Evolution

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Evolution

• The most basic definition of evolution is change
  over time
• In biology, it specifically refers to the change
  in the frequency of (9) over time within a
  population
• According to the theory of evolution,
  populations, not individuals, evolve
• We are stuck with the alleles were born with we
  cant evolve or change them

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The theory of evolution

• In science, a theory is defined as a hypothesis
  for which there is such a substantial amount of
  supporting evidence that it is regarded as fact
  by scientists
• Example Apples fall from trees, that is a fact.
  Why they fall is explained by the theory of
  gravitation. Electricity is also based upon
  scientific theory, but none of us dispute its
  reality

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How does evolution happen?

• There are 5 main mechanisms by which evolution
  can occur in a population
• 1. Genetic drift
• 2. Gene flow
• 3. Mutation
• 4. Non-random mating
• 5. NATURAL SELECTION

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Natural Selection

• Discovered by Charles Darwin in the 19th
  century after his trip to the Galapagos Islands
  aboard the H.M.S. Beagle
• Had been studying to qualify as a clergyman
  before setting off at age 22

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Natural Selection

• Based upon his observations, Darwin came up with
  4 postulates that make up his theory
• 1. Within any population there is variation
• 2. Some of that variation is hereditary
• 3. More offspring are produced than can survive
  each generation
• 4. Those offspring that survive do so in part
  because they have the best alleles they are
  naturally selected

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Is there evidence for evolution natural
selection?

• YES
• Lets examine the bone structure of the forelimbs
  of several different kinds of mammal

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The exact same bones are present in all three
organisms, even though the limbs are used for
markedly different purposes
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Another example
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Still more evidence

• Fossil record
• Geographic distribution of related species
  (closely related species tend to live near one
  another)
• Recorded genetic changes that we have been able
  to measure
• Artificial selection
• Remember, evolution only means a change in
  allele frequencies over time

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Why the debate?

• Evolution vs. Creationism/Intelligent Design
  (ID), Science vs. Religion, etc.
• The real debate is about whether non-science
  should be passed off as being science
• Lets revisit the scientific method from Week 1

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More on genetics

• Wildlife biologists want to consider a few other
  issues regarding genetics
• 1. Inbreeding
• 2. Founder effect
• 3. Outbreeding

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Inbreeding

• Can occur when populations are (10)
• May result in a loss of genetic (11)
• Inbreeding is most common in (12) situations such
  as labs, farms, zoos, etc.
• Nature has ways of minimizing the likelihood of
  inbreeding

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Founder Effect

• This is the result of a few individuals
  colonizing or founding a new area
• This ultimately leads to inbreeding, the effects
  of which can never be undone

Original popn
Possible founder groups
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Outbreeding

• In some ways, the extreme opposite of inbreeding
• This occurs when organisms mate with their most
  (13) relatives
• Adaptations for their specific environments may
  be lost, which is problematic results in lower
  (14) of the offspring