Mastering Biology Chapter 14 Study Guide

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)

What is the probability that Charles and Elaine will have a baby with cystic fibrosis? Express your answer as a fraction using the slash symbol and no spaces (for example, 1/16).

1/6

Based on this incomplete information, calculate the probability that if this couple has a child, the child will have sickle-cell disease. Express your answer as a fraction using the slash symbol and no spaces (for example, 1/16).

1/9

What percentage of cross-eyed tigers will be white? Express your answer using the percent symbol and no spaces (for example, 10%).

100%

In maize (corn plants) a dominant allele I inhibits kernel color, while the recessive allele i permits color when homozygous. At a different locus, the dominant allele P causes purple kernel color, while the homozygous recessive genotype pp causes red kernels. If plants heterozygous at both loci are crossed, what will be the phenotypic ratio of the offspring? _____ colorless: _____ purple: _____ red

12:3:1

Part A: If two phenotypically normal tigers that are heterozygous at this locus are mated, what percentage of their offspring will be cross-eyed? Express your answer using the percent symbol and no spaces (for example, 10%).

25%

In mice, black fur (B) is dominant to white (b). At a different locus, a dominat allele (A) produces a band of yellow just below the tip of each hair in mice with black fur. This gives a frosted appearance known as agouti. Expression of the recessive allele (a) results in a solid coat color. If mice that are heterozygous at both loci are crossed, what is the expected phenotypic ratio of their offspring? _____ agouti: _____ black: _____ white

9:3:4

When a dominant allele coexists with a recessive allele in a heterozygote individual, how do they interact with each other?

They do not interact at all.

Various procedures can be used to detect genetic disorders before birth. Among the tests discussed in this chapter, which is the least invasive (list first), and which two allow the chromosomes of the fetus to be examined?

ultrasound imaging ... chorionic villus sampling ... amniocentesis

Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height?

a combination of polygenic inheritance and environmental factors

Part A: A black guinea pig crossed with an albino guinea pig produces 12 black offspring. When the albino is crossed with a second black one, 7 blacks and 5 albinos are obtained. What is the best explanation for this genetic outcome?

Albino (b) is a recessive trait; black (B) is a dominant trait.

Individuals III-3 and III-4 are expecting their first child when they become aware that they both have a family history of this recessive condition. As their genetic counselor, you can calculate the probability that they are carriers and that their child will be affected with the condition.

1. 2/3 2. 1/2 3. 1/12

Assuming that both parents are heterozygous for the gene that causes the disease, what is the probability that the second child will also have the disease? Express your answer as a fraction using the slash symbol and no spaces (for example, 1/2).

1/16

Two organisms with genotype AaBbCcDdEE mate. These loci are all independent. What fraction of the offspring will have the same genotype as the parents?

1/16

Part A: What fraction of this couple's children would be expected to have extra digits? Express your answer using the slash symbol and no spaces (for example, 1/16).

1/2

Select the correct explanation for the fact that a carrier of a recessive genetic disorder does not have the disorder.

Affected individuals have recessive mutations, but a carrier has a dominant mutation.

Part B: What are the genotypes of the parents in the first cross (the cross that produced 12 black offspring)?

BB x bb

Part D: What are the genotypes of the parents in the second cross (the cross that produced 7 black and 5 albino offspring)?

Bb x bb

Which of the following do you expect if an individual is heterozygous for the sickle-cell trait?

He or she will show some symptoms of the disease.

Part A: What is the genotype of the man?

I A i

Part B: What is the genotype of the woman?

I B i

Pedigree 2 from Part A is shown below. Recall that this pedigree shows the inheritance of a rare, autosomal dominant condition. Fill in the genotypes for the indicated individuals in the pedigree by dragging the best label to the appropriate location. Labels can be used once, more than once, or not at all.

I- Dd II- Dd, dd, Dd III- dd, Dd, dd

Note that individual II-3 has no family history of this rare condition. Fill in the genotypes for the indicated individuals in the pedigree by dragging the best label to the appropriate location. Labels can be used once, more than once, or not at all.

I- rr II- Rr, RR, Rr III- R_, R_, R_

Which of the following is true about a plant with the genotype AABbcc?

It is homozygous at two loci.

Folk singer Woody Guthrie died of Huntington's disease, an autosomal dominant disorder. Which statement below must be true?

It is very likely that at least one of Woody Guthrie's parents also have had the allele for Huntington's disease.

In his breeding experiments, Mendel first crossed true-breeding plants to produce a second generation, which were then allowed to self-pollinate to generate the offspring. How do we name these three generations?

P ... F1 ... F2

Quantitative characters vary in a population along a continuum. How do such characters differ from the characters investigated by Mendel in his experiments on peas?

Quantitative characters are due to polygenic inheritance, the additive effects of two or more genes on a single phenotypic character. A single gene affected all but one of the pea characters studied by Mendel.

You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits?

Red shows incomplete dominance over white.

Look at the Punnett square, which shows the predicted offspring of the F2 generation from a cross between a plant with yellow-round seeds (YYRR) and a plant with green-wrinkled seeds (yyrr). Select the correct statement about wrinkled yellow seeds in the F2 generation.

The chance that an individual taken at random from the F2 generation produces wrinkled seeds is 25% and the chance that the same individual produces yellow seeds is 75%.

Each chromosome in this homologous pair possesses a different allele for flower color. Which statement about this homologous pair of chromosomes is correct?

These homologous chromosomes represent a maternal and a paternal chromosome.

John and Jane Jones' newborn baby girl, Leah, has just been diagnosed with galactosemia. Prior to their genetic counseling appointment, they submitted this family history: John and Jane's older child, a son named Lee, does not have galactosemia. John is the only child of Hanna and Harry. Harry was an only child. Hanna has two older sisters, Hope (the oldest) and Holly. Both Harry and Hanna's parents lived in good health into their 80s. Jane's brother, Joe, is married to Jen. They have a son, Les, who is a healthy nine-year-old with myopia (nearsightedness) but no sign of galactosemia. Jane's mother, Hilda, is alive and healthy; Jane's father, Henry, passed away last year of a sudden heart attack. Hilda and Henry have no family history of galactosemia. Use the information in the family history to construct a pedigree for this family.

Top row (left to right): Hanna's father, Harry's father 2nd row (left to right): Hilda, Hope, Holly, Hanna, Harry 3rd row (left to right): Jen, Joe, Jane, John 4th row (left to right): Les, Lee, Leah(THIS IS THE ONLY ONE THAT IS RED)

Part E: In what frequencies would you expect the offspring genotypes? Indicate the frequency of each genotype by dragging the labels to the table. Labels may be used once, more than once, or not at all.

all are 1/4

What is an allele?

an alternative version of a gene

The pedigrees below show the inheritance of three separate, rare autosomal conditions in different families. For each pedigree, decide if the condition is better explained as recessive or dominant. Drag the correct label to the appropriate location. Labels can be used once, more than once, or not at all.

autosomal dominant reaction, autosomal dominant reaction, autosomal 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

Consider pea plants with the genotypes GgTt and ggtt . These plants can each produce how many type(s) of gametes?

four ... one

Part E: What are the genotypes of the gametes and offspring in the second cross?

gametes: 1/2 B and 1/2 b (heterozygous parent) and b; offspring: 1/2 Bb and 1/2 bb

Part C: What are the genotypes of the gametes and offspring in the first cross?

gametes: B and b; offspring: all Bb

Part C: What is the genotype of the child?

ii

Part D: What genotypes would you expect in future offspring from this marriage? Select all that apply.

ii I A i I B i I A I B

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)