Warm-upComplete these crosses. Give the possible genotypic

results and phenotypic results. 1.Free ear lobes are dominant to attached ear lobes

in humans. If a recessive male marries a homozygous dominant female, what will be the phenotypic and genotypic ratios of their offspring?

2.Give the phenotypic and genotypic ratios of the possible offspring produced, when a heterozygous brown-eyed man marries a heterozygous brown-eyed woman. Brown eyes are dominant over blue eyes which are recessive.

Agenda

• Warm-up• Notes• Practice Worksheets• Whiteboards• Clean-Up• Cool-down

Announcements

• Quiz Tuesday Punnett Squares.

Genetics Part II

each trait is inherited independent of other traits

(chance)

Independent Assortment

in meiosis two alleles separate so that each gamete (sex cell)

receives only one form of the gene from each parent

Segregation

Mendel’s Principles of Inheritance• Inherited traits are transmitted by genes which

occur in alternate forms called alleles• Principle of Dominance - when 2 forms of the

same gene are present the dominant allele is expressed

• Principle of Segregation - in meiosis two alleles separate so that each gamete receives only one form of the gene

• Principle of Independent Assortment - each trait is inherited independent of other traits (chance)

If we saw an organism that had round seeds (round is dominant), how could we

figure out what its genotype is?

TEST CROSS!

A cross between an unknown and a

homozygous recessive

Test Cross

Example of a Test Cross

Unknown

When a combination of the dominant and recessive

creates a new phenotype. RR = red

rr = white Rr = pink

Incomplete Dominance

• Incomplete Dominance-When an intermediate between the dominant and recessive is expressed

Incomplete Dominance

RR Rr rr

Incomplete Dominance Cross

Incomplete Dominance Cross

• Polygenic traits are traits that are influenced by several genes. Examples include human height and skin color, which are both influenced by dozens of genes.

• As a result of polygenic traits, a lot of intermediate conditions exist.

• Genes with 3 or more alleles have multiple alleles. An example of multiple alleles is blood (IA, IB, IO)

Polygenic Trait

Blood Type

• The four Blood types are: A, B, AB, and O that come from the three alleles IA, IB, IO

• A and B are codominant, and they are also dominant to O.

• Type A = IAIA or IAIO, Type B = IBIB or IBIO, Type AB = IA IB, and Type O = IOIO

• Codominance-neither allele is dominant, but both are expressed at the same time

IT’S A MUST

• When a combination of the dominant and recessive allele make a new intermediate trait...

• Incomplete dominance

• Situation where neither allele is dominant, but both are expressed at the same time

• codominance

• What is a cross between an unknown and a homozygous recessive?

• Test cross

• What are the possible genotypes of Type A blood?

• IAIA or IAIO

• Draw the punnett square of the cross between a male with Type AB blood and a female with Type O blood.

• What is the genotypic and phenotypic ratio of the cross?

• 2 IAIO: 2 IBIO

• 2 type A blood : 2 type B blood

• Draw the cross and give the genotypic and phenotypic ratios of the cross of a red flower and a pink flower.

• Red- hom. dom• Pink- het.• White- hom. rec.

You found a tall pea plant. Explain how you would determine the genotype of this plant.

*Hint in pea plants, short height is recessive.

a.What are the possible genotypes of the plant?b. Draw Punnett squares for your possible crosses.c. You have 24 offspring, 24 tall and 0 short plants.

What was the genotype of the plant?

• Clean up this room!!

• That means…•No paper or trash on the floor•Chairs tucked under the desks•Desks straight

• THANK YOU!!

Cool-Down

1- Give an example of a phenotype and a genotype.

2- What is the difference between homozygous and heterozygous?

3- Perform a cross with RR x rr? What % of offspring would express the dominant trait?