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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 . 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

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

  2. Introduction • Is the following sentence true or false? Mendel’s work on inheritance was published after Darwin’s lifetime. • FALSE

  3. 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.

  4. How Common Is Genetic Variation All organisms have additional __________that is “invisible” because it involves small differences in biochemical processes. genetic variation

  5. Variation and Gene Pools • A group of individuals of the same species that interbreed is a(an) ____. • population

  6. GENE VARIATION • All of the genes in a population are called a(an)____. • gene pool

  7. GENE VARIATION • Is the following sentence true or false? • A gene pool typically contains just one allele for each inheritable trait. • false

  8. 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

  9. GENE VARIATION

  10. Evolution of Populations Sources of Genetic Variation • What is a mutation? • It is any change in a sequence of DNA.

  11. 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.

  12. GENE VARIATION • Circle the letter of each choice that is true about mutations. • They do not always change an amino acid

  13. 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

  14. 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.

  15. 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

  16. GENE VARIATION • Is the following sentence true or false? • Most traits are controlled by a single gene. • false

  17. 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

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