What is Genetics? Objectives: 1. Explain the history of genetics. 2. Explain how genetics works. 1

Genetics is the study of heredity. Heredity is the passing of traits from parent to offspring. Your eye color, hair color, shape of your nose, etc...

Traits A trait is a characteristic that you receive from your parents Traits A trait is a characteristic that you receive from your parents. For example: brown hair, blue eyes Alleles Different forms of a gene. Dominant alleles- traits that cover up or masks other traits Recessive alleles- traits that are masked and seem to disappear

What controls our traits? Genes are found on our chromosomes. Genes are made up of DNA. Human body cells have 23 PAIRS of chromosomes…our sex cells have only 23 (total). Why?

Gregor Mendel - Father of Genetics Lived in 1800’s in Eastern Europe Was taught about plants by Father Became a monk Famous experiment with plants. Died without ever knowing his work would become famous

Dominant and Recessive Factors Dominant traits appear to dominate or cover up other traits. Recessive traits appear to disappear…but do they?

Alleles Homozygous Heterozygous Two alleles for a trait that are exactly the same. Example: TT or tt Heterozygous Two alleles for a trait that are different. Written as Tt

Genotypes The inherited combination of alleles Represented by letters Ex. The letter P might stand for purple flowers in peas

Phenotypes Are physical traits that show as a result of a particular genotype. Examples Red is the phenotype for red flowering plants Brown hair Blue eyes Tall Short

Species Trait Individual Trait Traits that are carried by all members of a species. Example: The ability to walk upright in humans. Individual Trait Traits that make the individual different from others of the same species. Example: color of eyes, hair color, body build

Incomplete Dominance Can you explain how colors in flowers, for example, are blended? (For example, red and white alleles make pink flowers) When both alleles are expressed in offspring, the condition is called incomplete dominance…in other words, no allele is dominant. Read pages 243. Draw within a Punnett Square Mendel’s experiments with red and white flowers.

Multiple Alleles Many traits have more than 2 alleles that control them. Blood is an example of a multiple allele. Blood has 3 alleles. 3 major blood types: A B O

Punnett Squares y y Yy Y Yy Yy Yy Y *A tool used to predict results in genetics. *Uses your knowledge of dominant and recessive alleles. y y Yy Y Yy Yy Yy Y

Punnett Squares Shows genetic makeup or genotype of an organism. A capital letter (G) stands for a dominant allele. A small letter (g) stands for a recessive allele. Every cell in body has 2 alleles for a trait.

Practice using Punnett Squares Now let’s practice using Punnett squares!