BELLRINGER

1. What is your definition of genes?2. What would you like to learn about

genetics?3. Name one of your new years

resolution and how you will obtain that goal. (make your goal: SMART – Specific, Measurable, Attainable, Reasonable, Timely)

Genetics

What is Genetics

Genetics is the scientific study of heredity.

Heredity is what makes each species unique.

History

Gregor Mendel

Austrian Monk Famous for his work with pea plants He is known as the father of

genetics Fertilization: during sexual

reproduction where male and female reproductive cells join.

Mendel

Mendel’s Work

Mendel used true-breeding plants which means if they were left to breed with themselves they would produce offspring identical to themselves.

He preventing self-pollination by cutting away the pollen-bearing male parts of a plant and dusting those pollen to another plan, a process called cross-pollination.

Mendel studied 7 different traits in pea plants. A trait is a specific characteristic that varies

from one individual to another.

More on Mendel’s Work

Hybrids are offspring from parents with different traits.

Genes are the chemical factors that determine a trait.

The different forms of a gene are called alleles.

The Principle of Dominance

The principle of dominance states that some alleles are dominant and others are recessive.

Dominant alleles are always expressed.

Recessive alleles are only expressed if both alleles are recessive.

Segregation & Independent Assortment

The separation of alleles during meiosis to form gamates (sex cells).

The Law of Independent Assortment states that genes for different traits can segregate independently during the formation of gamates.

Laws of Inheritance

Probability & Genetics

Probability is the likelihood that an event will happen.

The principle of probability can be used to predict the outcomes of genetic crosses.

Probability

Punnett Squares

Diagram used to predict genetic crosses.

Individuals with identical alleles are called homozygous

Individuals with different alleles are called heterozygous

Phenotype – physical characteristic Genotype – genetic makeup

How to use Punnett Squares

Choose a letter to represent the alleles in the cross.

Write the genotypes of the parents. Determine the possible gametes

(reproductive cells) that the parent can produce.

Enter the possible gamete at the top and side of the Punnett square.

More Punnett Squares

Complete the Punnett square by writing the alleles from the gametes in the appropriate boxes.

Determine the phenotypes of the offspring.

Using the results of step E and F write down the genotypic and phenotypic ratios.

Naked Punnett Square

Punnett Squares Monohybrid & Dihybrid Crosses

Punnett Squares

Mendel’s Principles

The inheritance of biological characteristics are determined by genes.

For two or more forms of a gene, dominance and recessive forms may exist.

Most sexually reproductive organisms have two sets of genes that separate during gamete formation.

Alleles segregate independently, known as independent assortment.

Beyond Dominant and Recessive

Incomplete Dominance – One allele is not completely dominant over the other. White flower crosses with a red = pink flower.

Codominance – Both alleles contribute to the phenotype. Red cow X White Cow = Roan Cow.

Multiple Alleles – More than two alleles control the phenotype. Coat color of rabbits.

Polygenic traits – Several genes control the trait. Skin color in humans.

Examples

Complete The Following Punnett Squares

Round: RRWrinkled: r

R R

r

r

Round RYellow: Y

Wrinkled: rGreen: y

RY Ry rY ry

RY

Ry

rY

ry

Tall: TShort: t

T T

T

t

Complete the following Punnett Squares. Then, write the genotype and phenotype for each of the offspring

Quick Lab on Page 268Get your book and turn to page 268. Read the directions. I will pass out the graph paper and the colored pencils. Displayed here are the telephone numbers. Pick whichever you want.