Sources of Inherited Variation Mutations & Sexual Reproduction

Something to Ponder… Why do you think knowledge of chromosomes and genes are important in understanding Evolution? Why do you think knowledge of chromosomes and genes are important in understanding Evolution?

MUTATIONS DNA is found in the chromosomes of a cell. DNA is found in the chromosomes of a cell. DNA is composed of long sequences that form a code, which when translated by the cell, gives an organism specific inherited traits. DNA is composed of long sequences that form a code, which when translated by the cell, gives an organism specific inherited traits. Genes are segments of DNA that code for specific traits. Each gene has a specific DNA sequence. Genes are segments of DNA that code for specific traits. Each gene has a specific DNA sequence.

MUTATIONS…continued Though DNA typically remains the same throughout life, sometimes changes will occur. Though DNA typically remains the same throughout life, sometimes changes will occur. MUTATIONS are random changes in the DNA itself, and they provide a continuous supply of new genetic information. MUTATIONS are random changes in the DNA itself, and they provide a continuous supply of new genetic information.

How Do Mutations Happen? Environmental factors such as chemicals or radiation. Environmental factors such as chemicals or radiation. Errors that arise when cells use or make copies of the DNA molecules. Errors that arise when cells use or make copies of the DNA molecules. Many types of mutations… Many types of mutations… Some involve the loss or duplication of entire sections of DNA. Some involve the loss or duplication of entire sections of DNA. Some involve simple changes to the DNA sequence. Some involve simple changes to the DNA sequence.

Mutations are relatively rare in individuals, roughly about one new mutation per sex cell. Mutations are relatively rare in individuals, roughly about one new mutation per sex cell. In large populations reproducing over many generations, however, the number of mutations is substantial. In large populations reproducing over many generations, however, the number of mutations is substantial.

Types of Mutations Neutral Mutation – a mutation that has no effect on the organism. Neutral Mutation – a mutation that has no effect on the organism. Harmful Mutation – a mutation that reduces and organism’s fitness. Harmful Mutation – a mutation that reduces and organism’s fitness. Beneficial Mutation – a mutation that enhances an organism’s fitness. Beneficial Mutation – a mutation that enhances an organism’s fitness. Fitness – an organism’s reproductive success Fitness – an organism’s reproductive success **most mutations are neutral or harmful **most mutations are neutral or harmful

Sexual Reproduction & Variability READ PAGES 154 & 155 READ PAGES 154 & Why is there a greater amount of inherited variability in sexually reproducing organisms compared to asexually reproducing organisms? 1. Why is there a greater amount of inherited variability in sexually reproducing organisms compared to asexually reproducing organisms? 2. Why are sexually-reproducing species so variable? Describe, in detail, three reasons. 2. Why are sexually-reproducing species so variable? Describe, in detail, three reasons. 3. Connect Darwin’s Theory of Evolution with Genetic Mechanisms 3. Connect Darwin’s Theory of Evolution with Genetic Mechanisms