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Genes and Variation. 16-1 This section describes the main sources of heritable variation in a population. It also explains how phenotypes are expressed. . Introduction . Is the following sentence true or false? Mendel’s work on inheritance was published after Darwin’s lifetime. FALSE.

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genes and variation
Genes and Variation

16-1 This section describes the main sources of heritable variation in a population. It also explains how phenotypes are expressed.

introduction
Introduction
  • Is the following sentence true or false?

Mendel’s work on inheritance was published after Darwin’s lifetime.

  • FALSE
darwin s origin of species
DARWIN’s ORIGIN of SPECIES
  • Which two important factors was Darwin unable to explain without an understanding of heredity?
  • He was unable to explain the source of variation and how heritable traits were passed from one generation to the next.
how common is genetic variation
How Common Is Genetic Variation

All organisms have additional __________that is “invisible” because it involves small differences in biochemical processes.

genetic variation

variation and gene pools
Variation and Gene Pools
  • A group of individuals of the same species that interbreed is a(an) ____.
  • population
gene variation
GENE VARIATION
  • All of the genes in a population are called a(an)____.
  • gene pool
gene variation1
GENE VARIATION
  • Is the following sentence true or false?
  • A gene pool typically contains just one allele for each inheritable trait.
  • false
gene variation2
GENE VARIATION
  • The number of times that an allele occurs in a gene pool compared with the number of times other alleles for the same gene occur is called the _______of the allele.
  • relative frequency
evolution of populations
Evolution of Populations

Sources of Genetic Variation

  • What is a mutation?
  • It is any change in a sequence of DNA.
gene variation4
GENE VARIATION
  • Why do mutations occur?
  • They occur because of mistakes in the replication of DNA or as a result of radiation or chemicals in the environment.
gene variation5
GENE VARIATION
  • Circle the letter of each choice that is true about mutations.
    • They do not always change an amino acid
gene variation6
GENE VARIATION
  • Is the following sentence true or false?
  • Most heritable differences are due to gene shuffling that occurs during the production of gametes.
  • TRUE
gene variation7
GENE VARIATION
  • Circle the letter of each choice that is true about sexual reproduction.
  • It is a major source of variation in many populations.
  • It can produce many different phenotypes.
  • It can produce many different genetic combinations.
gene variation8
GENE VARIATION
  • Single-Gene and Polygenic Traits
  • Is the following sentence true or false?
  • The number of phenotypes produced for a given trait depends on how many genes control the trait.
  • TRUE
gene variation9
GENE VARIATION
  • Is the following sentence true or false?
  • Most traits are controlled by a single gene.
  • false
genetic variation
GENETIC VARIATION

Label the two graphs to show which one represents a single-gene trait and which one represents a polygenic trait.

Polygenic Trait Single-Gene Trait