CHAPTER CHAPTER 1111

Introduction to Genetics

Gregor Mendel

• Austrian monk who worked with true-breeding pea plants

• He cross-pollinated them

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Basics of What Mendel Learned

• Genes passed from parents to offspring

• Dominant allele that will show up• Recessive allele that will not show

up• Alleles separate independently

Allie Presher

Phenotypes vs. Genotypes

Examples of phenotypes:1. Tall pea plants2. Brown hair in humans

Examples of genotypes:1. TT homozygous

Tt heterozygoustt homozygous

2. BB

Bb

bb

Allie Presher

Punnett Squares

Punnett squares show the probability of possible outcomes of certain traits in organisms.

Angela Nguyen

Incomplete Dominance and Codominance

Angela Nguyen

Example of Incomplete Dominance:

Example of Codominance:

Polygenic Traits

• Controlled by two or more genes– Example:

Skin color in humans

Angela Nguyen

Meiosis

Allie + Angela

Linked Genes

• Genes that are on the same chromosome: they stay together– Example:

Black body and reduced bristles on fruit flies

Allie Presher