Chapter 7Unit 5

Genetics

Essential Questions1. What are traits?

2. What is the difference between self-pollination and cross-pollination?

3. What were the steps of Mendel’s experiments?

4. What is a recessive allele and dominant allele?

5. Why do children look like their parents?

6. How do you use a punnett square?

7. What is the difference between a heterozygote and homozygote?

8. What is the difference between a genotype and phenotype?

9. What is a mutation and how do they cause disorders?

10. How is a pedigree used in genetic counseling?

7-1 Genetics

trait: a variation of a particular characterEx yellow or red flowers

gene: a unit of inherited information

Gregor Mendel19th 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 ExperimentP generation= parental

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 Hypotheses1. There are alternate forms of genes

alleles: the alternate forms of genes Ex. Purple and white

2. 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

1. Pp; P = dominant, p = recessive

Punnett square: Diagram that shows all possible outcomes of a genetic cross

7-2 Inheritance

Phenotype and Genotype phenotype: an observable trait

Hair color, height, tongue rollingThe dominant trait shows upBb 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 coloringEx siamese cats,

rabbits

Height can be affected by nutrition and exerciseEx. 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

Pedigreepedigree: a family

tree that records and traces the occurrence of a trait in a familysquares = males ;

circles = femalescolored shapes =

individual with traithalf-colored =

carrier

Genetic counselors: use pedigrees to predict chances of a disorder