DNA, Mutations, Chromosomes, and Reproduction Review

1. DNA, Mutations, Chromosomes, and Reproduction Review

2. DNA: The Genetic Code • Genes • main function is to control the production of proteins in an organism’s cells. • Proteins help to determine the size, shape, color, and many other traits of an organism

3. DNA Structure • DNA structure • 4 Nitrogen bases: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C). • Form the rungs of the DNA “ladder” • Adenine always binds with Thymine • Guanine always Binds Cytosine • RNA • Thymine is replaced by Uracil • So Adenine binds with Uracil

4. Genes • A section of DNA • Contains the information to code for one specific protein • Made up of a series of bases in a row

5. Making Proteins • During protein synthesis, the cell uses information from a gene on a chromosome to produce a specific protein

6. Mutations • Any change in a gene or chromosome • Can cause a cell to produce an incorrect protein during protein synthesis • The trait or phenotype may be different • Body cell mutations will not be passed on to offspring • If the mutation is in a sex cell, the mutation can be passed on to an offspring and affect the offspring’s phenotype

7. Question • If a cat gets hit by a car and loses a leg, does this mean it will have kittens that are also missing a leg?

8. Effects of Mutations • Introduce changes in an organism • Can be a source of genetic variety • Some are harmful, some are helpful, others are neither helpful nor harmful • A mutation is harmful if it reduces the organism’s chance for survival and reproduction

9. Chromosome Theory of Inheritance • Sutton discovered that sex cells contain half the number of chromosomes as body cells. • One set of alleles comes from the male parent; the second set comes from the female parent • Chromosome theory of inheritance • Genes are carried from parents to their offspring on chromosomes

10. Mitosis • Mitosis (asexual reproduction) • No change in genetic variability • No genetic loss from meiosis or recombination • Good in stable environments…ones that are NOT always changing • Occurs in body cells • Results in 2 cells • Results in cells with the same # of chromosomes as the original parent cell

11. Meiosis • Sexual Reproduction • Rearranging the genome creates variability • Almost 50% of genetic material is lost during recombination • Good in variable environments…ones that are always changing • Occurs only in sex cells • Results in 4 cells • Results in cells with half the chromosome # as the parent cell