GENETICS The study of Heredity!

Heredity- Deals with inherited traits Traits- Inherited characteristics (ex. Eye color) –Our DNA determines our traits (genes) Genetics- The study of heredity

Gregor Mendel 1 st person to study how traits were inherited He found that traits were passed from a parent to the offspring by studying a garden pea He was the 1 st to succeed in predicting traits Example: He crossed a tall pea plant with a short pea plant and found that all of the offspring were tall (TT x tt)

How are things inherited? When fertilization occurs, there are 2 traits given to the offspring –(1 from the mother and 1 from the father) Each parent contributes a trait –(1 trait is called an allele) –Ex. Dad may contribute a dark hair trait and the mother a light hair trait

2 kinds of traits: Dominant trait- strong trait- represented by a capital letter (ex. T) –The dominant trait will win out (show up) Recessive trait- weaker trait- represented by a lower case letter (ex. t)

During fertilization, alleles will randomly pair which will produce 4 different combinations called the Law of Segregation We use the punnett square to show the 4 different possible combinations that the offspring may get

Solving genetics problems Use the punnett square

Terms used in genetics problems: 1.Genotype- Shows the different gene combinations an offspring may have (example Bb) 2.Phenotype- The physical appearance of the offspring – ex. black hair 3.Homozygous allele- Both alleles are the same (ex. HH or hh) 4.Heterozygous allele- Both alleles are different (ex. Hh)

Terms contd. 5. Monohybrid cross- Cross of 1 trait (ex. Eye color) 6. Dihybrid cross- Cross of two traits (ex. eye color x hair color) We will be working with monohybrid crosses only!

Genetic problems—copy problems Must use punnett square and show letter of dominant/recessive 1. A homozygous dominant man with nonattached eyebrows crosses with a woman that has attached eyebrows. –What is the phenotype? Genotype? Percent attached eyebrow? 2. A woman that is heterozygous for dimples crosses with a man who is heterozygous for dimples. –What are the genotypes? Phenotypes? Ratio of dimples to no dimples? 3. A man who is heterozygous for freckles crosses with a woman who lacks freckles. –What are the phenotypes? Genotypes? Percent that do not have freckles? 4. A woman with a square face crosses with a man that is homozygous dominant for a round face. –What are the genotypes? Phenotypes? Ratio of round to square? 5. A woman who has heterozygous almond shaped eyes crosses with a man that is homozygous dominant for almond eyes (round is recessive) –What are the phenotypes? Genotypes? Percent of almond shaped?

A heterozygous man with normal joints marries a woman that is recessive for double joints. What are the genotypes? What are the phenotypes? What percent are double jointed?

Problems 1. A woman that is heterozygous for a big mouth crosses with a man that has a small mouth A. genotype? B. phenotype? C. ratio large to small

2. A homozygous dominant man for cleft chin crosses with a woman that lacks a cleft chin. A. phenotype B. genotype C. Percent non cleft

3. A homozygous dominant bushy eye browed crosses with a woman that is heterozygous bushy eyebrowed. A. genotypes? B. phenotypes? C. percent bushy?

drawing 1. Go to microsoft word Click on insert, then pictures, then autoshapes 2. When you have finished your drawing Save as: Shared drive (F), click on osborn, your period, file name should be your name Do not print!!!

Probability—likelihood of an event occuring Example: probability of inheriting a disease

pedigree