DNA, Mutations, Chromosomes, and Reproduction Review

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

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

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

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

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

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?

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

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

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

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