Honors Biology - Genetics

Genetics

The branch of Biology that is concerned with how characteristics are transmitted from parent to offspring.

Heredity

Deals with the passing on of characteristics from parents to offspring.

Traits

Consist of two genes.

Example of Traits

Eye and hair color

Gene

A segment of DNA that codes for a trait

Allele

A single gene

What plant did Mendel use and why?

Pea plants because they could self or cross pollinate. The also grow quickly so he could study multiple generations at the same time.

1st contrasting trait

Flower color (Purple and White)

2nd contrasting trait

Height

3rd contrasting trait

Color of the pea (Green or Yellow)

4th contrasting trait

Texture of the pea (smooth or wrinkled)

5th contrasting trait

Color of the pod (Green or Yellow)

6th contrasting trait

Texture of the pod (inflated or constructed)

7th contrasting trait

Flower position (axial or terminal)

Why did Mendel allow the plants to self pollinate?

So that they were pure for each trait.

Mendel’s Experiment - P1

A pure tall X A pure short

P1 Generation

Original Parents

Offspring of P1 Generation in Mendel’s Experiment

All tall

Mendel’s Experiment - F1 Generation

All tall plants

Results of the crossing of two F1 plants

¾ tall and ¼ short

Mendel’s Experiment- F2 Generation

¾ tall plants and ¼ short plants

Dominant Gene

Represented by a capital letter

Dominant Trait

If dominant gene is present, the dominant trait will show.

Recessive Gene

Represented by a lowercase letter

Recessive Trait

Two recessive genes must be present for a recessive trait to show.

Homozygous Trait

Contains 2 genes that are the same

Heterozygous

Contains two genes that are different

Phenotype

Physical characteristics a genotype produces

Examples of Phenotypes

Brown hair and blue eyes

Genotype

The actual allele combination of traits

Example of Genotype

BBttaakkGg

Law of Dominance

If a dominant gene is present, the dominant trait will show.

Law of Segregation

During Gamete formation, gene pairs for every trait will separate.

Gamete

Sex Cells (Sperm and Egg Cells)

Law of Independent Assortment

Gene pairs for every trait will separate independently from one another.

Probability

The chance that something will or will not happen.

Product Rule

The probability of more than one thing happening at the same time.

Punnett Squares

Used to determine the probability of the phenotypes and genotypes of offspring.

Monohybrid Cross

Crosses that involve one trait.

Phenotype Ratio

The number of offspring that will have the same physical trait.

Genotype Ratio

Number of allele combinations that are the same.

Dihybrid Cross

Involves 2 different traits

Incomplete Dominance

Neither gene is dominant or recessive.