Ch. 12 Genetics

A. Gregor Mendel (1822-1884) – The father of Genetics Mendel discovered the basic principles of heredity by breeding garden peas in carefully planned experiments.

Mendel defined different types of hybridization 1. P generation – parental; true breeding parents 2. F1 generation – 1st generation of offspring 3. F2 generation – 2nd generation of offspring

Trait Dominant Expression Recessive Expression Form of ripe seed (R) Smooth Wrinkled Color of seed albumen (Y) Yellow Green Color of flower (P) Purple White Form of ripe pods (I) Inflated Constricted

Principles of genetics  Traits are handed down from one generation to the next  Traits are controlled by genes  Genes are inherited in pairs, one from each parent

Some genes are dominant some are recessive Dominant genes can mask recessive genes when one of each is inherited Some genes are not dominant or recessive but blend when inherited together

B. Genetic Vocabulary 1. Chromosomes: hereditary units of an organism 2. Allele – One gene of gene pair for a trait. for example: In the gene pair Bb for hair, color both B & b are alleles 3. Homozygous – pair of identical alleles for a character BB = Brown

4. Heterozygous – having 2 different alleles for a character. 5. Haploid = contains one copy of each chromosome (meiosis) 6. Diploid = contains two copies of each chromosome (mitosis) Bb = Brown

7. Genotype – an organism’s genetic makeup. BB or Bb 8. Phenotype – an organism’s outward appearance. 9. Mutations: changes in genetic material Brown eyes

10. Karyotype: an enlarged photograph of the chromosomes in an organism

11. Multiple alleles - when more than 2 alleles control a trait 11. Multiple alleles - when more than 2 alleles control a trait. Example human blood. A dominant, B dominant, O recessive

12. Sex linked traits - gene for a trait is carried on one of the sex chromosomes. example color blindness, hemophilia XX- Female XY - Male 13. Meiosis - production of gametes (sperm or egg cells) which contain half the normal number of chromosomes

C. Ways to determine inherited traits - Predicting traits Punnett square – a square used to show all the possible combinations of gametes. A homozygous brown–eyed mother mates with a blue – eyed father. What ratio of brown–eyed to blue–eyed children will they have? Brown eyes is the dominant trait

phenotypic ratio is: B B b genotypic ratio is: B b Bb Bb B BB Bb Bb Bb B- brown eyes b- blue eyes BB x bb B B b genotypic ratio is: phenotypic ratio is: B b Bb Bb B BB Bb Bb Bb Bb bb b 100 % Bb 100 % Brown

2. Determining parental genotypes Pedigree Test – Test in which you look at the offspring of parents to determine the genotypes of the parents. The squares are for males and the circles are for females. If the symbol has been darkened it says the person carries the trait.