2022 EOC Review Day 9 - Genetics

2022 EOC Review Day 9 - Genetics

​This review is self-paced, but we will go through it together in class.

​

Please make sure you finish the questions at the end of the review and the handout.

​

The handout counts as your subjective final. The review will count towards minor grades.​

105. Define

​

• Dominant - allele that overrides another allele. Written as a capital letter (A, T, Y, etc)

• Recessive - allele that gets overridden by another allele. Written as a lower case letter (a, t, y, etc).

• Homozygous - two of the same allele (Example: AA, aa)

• ​Heterozygous - two different alleles (Example: Aa, Tt)

• Genotype - allele combination that codes for a particular trait (Example: TT - tall; tt - short; Bb - brown eyes)

• Phenotype - physical characteristics determined by the genotype (Example: tall, short, brown hair, blue eyes)

106. a. Monohybrid Cross

Two heterozygous tall plants are crossed. If tall is dominant over short, what are the expected phenotypic results?

(Show your work!)​

Monohybrid Cross

Phenotypes:

75% TALL  (TT, Tt),  25 % SHORT (tt)

 

Multiple Choice

106b. If one homozygous short plant is crossed with a heterozygous tall plant, what percentage of the offspring will be short?

• 0% short, 100% tall

• 25% short, 75% tall

• 50% short, 50% tall

• 75% short, 25% tall

Incomplete Dominance

Sometimes a dominant allele is not completely dominant.

​

In that case, there is a mixing between the two traits.

​

RR: red flower

WW: white flower

RW: pink flower​

108. Incomplete Dominance

When Red and white flowers are crossed, pink flowers are produced. What is expected when two pink flowers cross?

​

RR: red flower

WW: white flower

RW: pink flower​

Multiple Choice

108. When Red and white flowers are crossed, pink flowers are produced. What is expected when two pink flowers cross?

• 25% red; 50% pink; 25% white

• 50% red; 50% pink

• 100% pink

• 50% red; 50% white

Codominance

When two different alleles are equally dominant, they BOTH get expressed.

​

This happens sometimes in cattle.

​

It also happens with bloodtypes.

Codominance

Mr. Jones has blood type I^A i and Mrs. Jones has blood type I^B i.

​

What is the probability that they will have a child with blood type ii?

Multiple Choice

109. What is the possibility for a man who is heterozygous for blood type A crossed with a woman with type AB blood to have a child with type A blood?

• 0%

• 25%

• 50%

• 75%

110. Is it possible for a man with type A blood and woman with type B blood to have a child with type O blood?

​

I^A i x I^B i​

Multiple Choice

If a man who is heterozygous for type A blood has a child with a woman who is heterozygous for type B blood, what are the chances their child will have type O blood?

• 0%

• 25%

• 50%

• 75%

111. Pedigrees

Square = male

Circle = female

​

Shaded = has the trait

Unshaded = does not have the trait​

​

Is this pedigree showing a dominant or recessive trait?

​

​

111. Pedigrees

Is this pedigree showing a dominant or recessive trait?

​

Remember that recessive traits have a tendency to skip generations. ​

​

If the trait does not skip generations, it is probably dominant.​

​

​

Multiple Choice

Is this pedigree showing a dominant or recessive trait?

• Recessive because the trait skips generations.

• Dominant because every generation has someone affected.

• Recessive because every generation has someone affected.

• Dominant because the trait skips generations.

Multiple Choice

112. What is most likely the genotype of individual II-1?

• AA

• Aa

• aa

• AAA

Multiple Choice

112. What is most likely the genotype of individual II-3?

• AA

• Aa

• aa

• AAA

Dihybrid Cross

To cross two traits, use the FOIL method:

​

First

Outer

Inner

Last

Dihybrid Cross

R: red eyes

r: black eyes

​

D: dark fur

d: light fur

Dihybrid Cross

Show a cross between:

​

RRdd x RrDD

​

Red eyes are dominant to black eyes and dark fur is dominant to light fur.

Multiple Choice

What percentage of offspring will be RRDd?

• 0%

• 25%

• 50%

• 100%

Multiple Choice

What percentage of offspring will have red eyes and dark fur?

• 0%

• (25%)

• (50%)

• (100%)

Multiple Choice

• F

• G

• H

• J

Multiple Choice

• F

• G

• H

• J

Sex-linked Traits

• Sex linked traits are carried on the sex chromosomes (X or Y). Males have XY, females have XX.

• Males will more commonly express the phenotype because they only have one X chromosome.

• Females will express the phenotype only if she inherits 2 copies because she has 2 X chromosomes. 

• Females can be carriers if the trait is recessive.

B - normal vision

b - colorblind

Color blindness is a sex-linked recessive trait. A woman with normal color vision is married to a man who is color blind.

​

What would be the phenotypic ratio of their offspring?

Multiple Choice

Color blindness is a sex-linked recessive trait. A mother with normal color vision and a color-blind father have a color-blind daughter.

Which of the following statements is correct?

• All of their daughters will be color blind.

• The mother is a carrier of the color blindness gene.

• All of their sons will have normal color vision.

• All of their sons will be color blind.