What is Genetics?

Objectives: 1. Explain the history of genetics.2. Explain how genetics works.

Genetics is the study of heredity.

Heredity is the passing of traits from parent to offspring.

TraitsA 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

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

Traits that are carried by all members of a species.

Example: The ability to walk upright in humans.

Traits that make the individual different from othersof the same species.

Example: color of eyes, hair color, body build

Incomplete DominanceCan 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.

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

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!