Chapter 7 Unit 5 Genetics

Essential Questions What are traits? What is the difference between self-pollination and cross-pollination? What were the steps of Mendel’s experiments? What is a recessive allele and dominant allele? Why do children look like their parents? How do you use a punnett square? What is the difference between a heterozygote and homozygote? What is the difference between a genotype and phenotype? What is a mutation and how do they cause disorders? How is a pedigree used in genetic counseling?

7-1 Genetics trait: a variation of a particular character Ex yellow or red flowers gene: a unit of inherited information

Gregor Mendel 19th century Austrian Monk First to apply an experimental approach to the question of inheritance genetics: the study of heredity Used pea plant breeding

Pollination pollination: the transfer of pollen from the male part to the female part of a plant (fertilization) cross-pollination: pollen from one plant pollinates another plant self-pollination: pollen from a plant pollinates itself

Mendel’s Experiment P generation= parental F1 generation = the hybrid Purple or white flowers Self-pollinate flowers to get “pure” flowers F1 generation = the hybrid offspring Cross-pollinated between white and purple All ended up purple F2 generation = offspring when F1 self- fertilize each other Purple flowers were self-pollinated Ended up with 75% purple, 25% white

Mendel’s Pea Plants

Mendel’s Hypotheses There are alternate forms of genes alleles: the alternate forms of genes Ex. Purple and white For each inherited character, an organism has 2 alleles for the gene controlling that character, one from each parent homozygous: 2 alleles are the same for that character heterozygous: the 2 alleles are different 3. dominant: only one allele appears to affect the trait recessive: the allele that does not appear to affect the trait Pp; P = dominant, p = recessive

7-2 Inheritance Punnett square: Diagram that shows all possible outcomes of a genetic cross

Phenotype and Genotype phenotype: an observable trait Hair color, height, tongue rolling The dominant trait shows up Bb and BB = dominant; brown bb = recessive; blond genotype: the genetic makeup (combination of alleles) 1/2 Bb; 1/2 bb = 2:2

Importance in the Environment Temperature can have an effect on animal coloring Ex siamese cats, rabbits Height can be affected by nutrition and exercise Ex. Dancers Nature vs Nurture

7-3 Genetic Disorders mutation: change in genes Can be harmful, helpful, or have no affect mutagens: physical or chemical agents that cause mutations Ex. High-energy radiation Most genetic disorders are caused by harmful recessive alleles

Pedigree pedigree: a family tree that records and traces the occurrence of a trait in a family squares = males ; circles = females colored shapes = individual with trait half-colored = carrier Genetic counselors: use pedigrees to predict chances of a disorder