Mastering Biology HW Chapter 14

True or false? The same phenotype can be produced by more than one genotype.

True

Now that you have determined the most likely genotypes that correspond to each phenotype, you will predict the results of a different mating. Suppose one parent is wild-type and the other is apterous. Using a Punnett square, set up this cross and predict the ratio of phenotypes. What phenotypic ratio do you predict?

1:1

The result of the following cross indicates that the genotype of the female parent is _____.

RR

In the video, the paternal parent carries the allele for purple flowers, and the maternal parent carries the allele for white flowers. What would happen if the maternal parent carried the purple allele, and the paternal parent carried the white allele?

The F1 hybrid pea plants would still produce purple flowers.

You continue your analysis by crossing the forked and twist lines. Your results are as follows: Which of the following statements best explains the outcome of this cross?

The forked mutation and the twist mutation are codominant alleles of the same locus. Submit

If Jane and John want to have another child, they plan to see a genetic counselor to find out when it would be best to test for galactosemia. A newborn with galactosemia must be put on a lactose- and galactose-free diet as soon as possible after birth. Even on this diet, affected individuals may still suffer from learning disabilities, ovarian failure (in young women), late-onset cataracts, and early death. Which of the following tests would be most useful for Jane and John to have?

newborn screening (either assaying for the GALT enzyme or measuring excess galactose in the newborn's blood)

A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)?

ttpp

In pea plants, the purple allele is sufficient for making purple flowers, even if one of the homologous chromosomes carries the white allele. Which of the following statements are true in this case?

-The white allele is the recessive allele. -The purple allele is the dominant allele. -One purple allele results in enough purple pigment for the flowers to be purple.

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the genotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

0 homozygous black (BB): 1 heterozygote (black) (Bb): 1 homozygous orange (bb)

If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?

None

The result of the following cross indicates that genotypically the offspring _____.

are all Rr

The result of the following cross indicates the orange eyes are _____ black eyes.

recessive to

The result of the following cross indicates that the genotype of the male parent is _____.

rr

In the following cross the genotype of the female parent is BbGg. What is the genotype of the male parent? [Hint: B = black eyes, b = orange eyes, G = green skin, g = white skin]

BBGg

How would you determine whether the curl allele is dominant or recessive?

Matings of the original mutant cat with true-breeding noncurl cats will produce both curl and noncurl F1F1 offspring if the curl allele is dominant, but only noncurl offspring if the curl allele is recessive.

Jane and John are considering having another child. Given the pedigree you constructed and the mode of inheritance for galactosemia, what is the risk that their next child will have the disorder?

1/4 (because they are both heterozygotes)

In a situation in which genes assort independently, what is the ratio of the gametes produced by an AaBB individual?

1 AB : 1 aB

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the phenotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

1 black : 1 orange

Black eyes are dominant to orange eyes, and green skin is dominant to white skin. A male MendAlien with black eyes and green skin, has a parent with orange eyes and white skin. A female MendAlien with orange eyes and white skin. If these male and female MendAliens were to mate, the predicted phenotypic ratio of their offspring would be _____.

1 black eyes, green skin : 1 black eyes, white skin : 1 orange eyes, green skin : 1 orange eyes, white skin

An individual heterozygous for eye color, skin color, and number of eyes mates with an individual who is homozygous recessive for all three characters; what would be the expected phenotypic ratio of their offspring? [Hint: B = black eyes, b = orange eyes; G = green skin, g = white skin; C = two eyes, c = one eye]

1 black eyes, green skin, two eyes : 1 black eyes, green skin, one eye : 1 black eyes, white skin, two eyes : 1 black eyes, white skin, one eye : 1 orange eyes, green skin, two eyes : 1 orange eyes, green skin, one eye : 1 orange eyes, white skin, two eyes : 1 orange eyes, white skin, one eye

One character in peas that Mendel studied was yellow versus green seeds. A cross between a homozygous yellow line (YY) and a homozygous green line (yy) will result in F1 plants that are heterozygous (Yy) for this trait and produce yellow seeds. When an F1 plant undergoes meiosis, what gamete types will it produce, and in what proportions?

1/2Y 1/2y

Suppose you mate two mice with the genotypes AYaBb x AYaBb . Considering only the live-born offspring, what would be the expected frequency of mice with yellow fur? (For help getting started, see Hint 1.) Express your answer as a fraction using the slash symbol and no spaces (for example, 1/16).

2/3

Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?

25

In mice, agouti fur is a dominant trait resulting in individual hairs having a light band of pigment on an otherwise dark hair shaft. A mouse with agouti fur is shown here, along with a mouse with solid color fur, which is the recessive phenotype (A = agouti; a = solid color). What would be the expected frequency of agouti brown offspring in the litter?

3/16

Albinism is a recessive condition in which homozygous individuals have decreased production of melanin in their skin, eyes, and hair. Individuals who are homozygous dominant or heterozygous exhibit normal melanin production. Suppose two people are heterozygous at this gene locus. They decide to have children and want to know what the chances are of their children having albinism. Using a Punnett square, set up this cross and predict the ratio of phenotypes. What phenotypic ratio do you predict?

3:1

In a cross between two mice that are heterozygous for agouti, black, color, and piebaldism, what is the probability that offspring will have solid black fur along with large patches of white fur? (Hint: Consider each gene separately; then use the multiplication rule. For more help getting started, see Hint 1.) Express your answer as a fraction using the slash symbol and no spaces (for example, 3/16).

9/256

A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____.

both parents are heterozygous for both genes

Which of these is a testcross?

A? x aa

What is the difference between heterozygous and homozygous individuals?

All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.

Now that you have determined which traits are dominant and recessive, you will use that information to determine the genotypes of the parents in a specific mating. Typically, alleles are identified using single letters, with uppercase letters representing the dominant allele and lowercase letters representing the recessive allele. You will use A� as the wild-type wing allele and a� as the apterous wing allele. 1. Reset the simulation and select wild-type for both parents. 2. Run the simulation five times so that you get a larger data set. (Do not reset the simulation in between runs.) What are the genotypes of each parent?

Both the male and female are Aa

How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?

Cross the green-pod plant with a yellow-pod plant

True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.

False

A BbGg x bbgg cross yields a phenotypic ratio of approximately 5 black eyes, green skin : 5 orange eyes, white skin : 1 black eyes, white skin : 1 orange eyes, green skin. Which of the following best explains these results?

Mendel's law of independent assortment is being violated.

That each gamete contains a single allele of the eye color gene is an illustration of _____.

Mendel's law of segregation only

The observed distribution of alleles into gametes is an illustration of _____.

Mendel's laws of segregation and independent assortment

You know that alleles are alternative versions of a gene. What makes alleles different from each other?

They have different sequences of DNA nucleotides.

To determine which allele is dominant, it is necessary to perform multiple matings of the two parents. 1. Reset the simulation and make sure wild-type is selected for both parents. 2. Run the simulation five times so that you get a larger data set. (Do not reset the simulation in between runs.) 3. Record the data in a table, or take a screenshot of the data table in the simulation. 4. Reset the simulation and select apterous for both parents. 5. Run the simulation five times so that you get a larger data set. (Do not reset the simulation in between runs.) 6. Compare the data from the apterous ×× apterous cross to the data from the wild-type ×× wild-type cross. Which trait is dominant and how do you know?

Wild-type wings are dominant because wild-type parents can produce apterous offspring, but apterous parents can't produce wild-type offspring

Because the inheritance pattern for albinism is the same as for Drosophila wings, you can use the simulation to test predictions about the human albinism trait. 1. Reset the simulation to its default settings. The wild-type flies are equivalent to the parents who are heterozygous for albinism. 2. Run the simulation five times without resetting between runs. Was your prediction of a 3:1 phenotypic ratio confirmed?

Yes, the ratio of unaffected to albino offspring was approximately 3:1 across all five runs.

Now test your prediction using the simulation. 1. Reset the simulation and select wild-type for one parent and apterous for the other parent. 2. Run the simulation five times. (Do not reset the simulation in between runs.) Was your prediction of a 1:1 phenotypic ratio confirmed?

Yes, the ratio of wild-type to apterous offspring was approximately 1:1 across all five runs.

How could you be sure they are true-breeding?

You know that cats are true-breeding when curl ×× curl matings produce only curl offspring.

How would you obtain true-breeding curl cats?

You would obtain some true-breeding offspring homozygous for the curl allele from matings between the F1F1 cats resulting from the original curl ×× noncurl crosses no matter whether the curl trait is dominant or recessive.

Look over the pedigree you constructed in Part A. Based on the inheritance pattern, which mode of inheritance must be the cause of galactosemia?

autosomal recessive

In order to determine the genotype of a MendAlien with black eyes and green skin, you would cross this individual with a(n) _____ individual.

bbgg

What is the genotype of the parent with orange eyes and white skin? (Note: orange eyes are recessive.)

bbgg

A cross between two individuals that are heterozygous for eye and skin color would be an example of a _____ cross.

dihybrid

When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.

gametes, progeny

Suppose that the botanist carried out the test cross described in Parts A and B and determined that the original green-pod plant was heterozygous (Gg). Which of Mendel's findings does her test cross illustrate?

law of segregation

During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur? State your answer as meiosis I or meiosis II followed by a comma and the name of the phase (for example, if your answer is meiosis II and metaphase, enter meiosis II, metaphase).

meiosis I, anaphase