Punnett Squares The Punnett square is a tool

Punnett Squares

• The Punnett square is a tool for understanding the patterns of heredity. • Show possible allele combinations • Shows the possible genotypes of offspring

Alleles and phenotypes

Image of genotype

Hybrid • Term used to describe a heterozygous organism • Ex: Tt

Co-dominance • Incomplete dominance • Occurs when each gene shows up independently(not recessive or dominate) • Ex: Chickens

Multiple Gene Inheritance • More than two genes control the trait • Ex) eye color, height, skin color

Traits • Qualities, features, things that distinguish one organism from another

Two types of traits • Inherited- come from our parents- carried on genes • Acquired- Developed over your lifetime (ability to swim)

Sex Linked Traits • Our gender (sex) is determined by sex chromosomes

• Female- XX 2”x” chromosomes • Male- XY 1”x” and 1”y” chromosome

• Genes on the X and Y chromosomes are called sex linked genes • Traits controlled by this are called sex linked traits

Examples • Hemophilia • Colorblindness

• There are certain traits that are only carried on the x chromosome • In a female a dominate trait on one “x” chromosome will mask the recessive trait

• In a male there is no matching trait so a recessive gene will produce the trait in the male who inherits is

Genetic Disorders

Genetic Disorders • Abnormal condition that a person inherits through genes of chromosomes • Caused by mutations or change in a persons DNA

Examples • Down syndrome • Sickle Cell Anemia • Cystic Fibrosis

• Down syndrome- caused by an extra chromosome (47 instead of 46)

• Sickle Cell- abnormal shaped blood cells. Shape makes them get stuck in blood vessels • Gives lack of oxygen /weakness

• Cystic Fibrosis- Produces thick mucus in lungs and intestines