Chapter 9

All the offspring of a cross between a black-eyed Mendelian and an orange-eyed Mendelian have black eyes. What is the expected phenotypic ratio of a cross between two orange-eyed Mendelian? 1 black-eyed:3 orange-eyed 3 black-eyed:1 orange-eyed 1 black-eyed:0 orange-eyed 0 black-eyed:1 orange-eyed

0 black-eyed:1 orange-eyed

ustin has type A blood and his wife Brittany has type B blood. Justin's parents both have type AB blood, and Brittany's parents also both have type AB blood. What are the chances that Justin and Brittany's son Theodore has type A blood? 100% 0% 25% 75%

0%

Suppose that an elephant with the genotype EEFfggHh reproduces with an elephant with the genotype eeFFGgHh. What is the probability that a baby elephant (called a calf) would have the genotype EeFFGghh? 1/64 1/256 1/16 1/32

1/16

Using a six-sided die, what is the probability of rolling either a 5 or a 6? 1/6 + 1/6 = 2/3 1/6 1/6 + 1/6 = 1/3 1/6 × 1/6 = 1/36

1/6 + 1/6 = 1/3

Assuming that the probability of having a female child is 50% and the probability of having a male child is also 50%, what is the probability that a couple's first-born child will be female and that their second-born child will be male? 75% 25% 50% 20%

25%

After reading the paragraphs below, answer the question that follows. During a summer study abroad program, you travelled to Austria to study genetics at the University of Vienna. While you were there, a momentous discovery was made: some of Gregor Mendel's original lab books and notes were found to be buried outside of the abbey where he lived. It just so happened that the professor you were working with obtained copies of these notes and enlisted your help to decipher them. You hired a translator to translate Mendel's notes from Czech to English, and using your knowledge of modern genetics (which Mendel did not have!) you were able to construct a partial Punnett square (shown below). Because the notebook was damaged from being buried for so long, this is the only information that you have regarding a cross that Mendel must have performed. Your professor has tasked you with figuring out more about this experiment. In pea plants, round peas are dominant (R) and shriveled peas are recessive (r), and yellow peas (shown as light gray in Punnett square) are dominant (Y) and green peas (dark gray) are recessive (y). Using this information and the partial Punnett square above, what is the phenotypic ratio of the offspring pea plants in this Punnett square? 1:1:1:1 3:3:1:1 12:1:1:4 9:3:3:1

3:3:1:1

If A is dominant to a and B is dominant to b, what is the expected phenotypic ratio of the cross AaBb × AaBb? 8:4:2:2 1:1:1:1 16:0:0:0 9:3:3:1

9:3:3:1

After reading the paragraphs below, answer the question that follows. Cats normally have a total of 18 toes, 5 on each front paw and 4 on each back paw. But some cats express the dominant phenotype for polydactyly, which results in the development of extra toes on one or more paws. Jake, a Canadian tabby cat, has 28 toes and is recognized by the Guinness Book of World Records as the cat with the most toes. Suppose that Jake mates with a female cat, Lucy, who has 18 total toes. Over several years, they have multiple litters and a total of 16 kittens (10 males and 6 females). The total number of toes on each kitten ranges from 21 to 25. Along with having a variable number of toes, some kittens from Jake and Lucy's litter had a white spot on their nose. In fact, out of the 16 kittens, all 10 males had the white spot, but none of the 6 females had the white spot. Jake has a white spot on his nose, but Lucy does not. What can you conclude from this information? A sex-linked gene that controls the expression of the white spot is found on the X chromosome. The genes for the white spot and for polydactyly are not linked. The genes for the white spot and for polydactyly are linked. A sex-linked gene that controls the expression of the white spot is found on the Y chromosome.

A sex-linked gene that controls the expression of the white spot is found on the X chromosome. V

Below are two statements. Which (if any) applies to the law of segregation? Which (if any) applies to the law of independent assortment? I: Phenotypes for long tails and big eyes are inherited separately in lab mice. II: A baby mouse inherits a maternal red eye allele and a paternal black eye allele. A: segregation; B: segregation A: independent assortment; B: independent assortment A: segregation; B: independent assortment A: independent assortment; B: segregation

A: independent assortment; B: segregation

Which of the following statements regarding genotypes and phenotypes is false? The expressed physical traits of an organism are called its phenotype. Alleles are alternate forms of a gene. The genetic makeup of an organism constitutes its genotype. An organism with two different alleles for a single trait is said to be homozygous for that trait.

An organism with two different alleles for a single trait is said to be homozygous for that trait.

Which of the following statements is false? Incomplete dominance supports the blending hypothesis. The impact of a single gene on more than one character is called pleiotropy. ABO blood groups can provide evidence of paternity. The four blood types result from various combinations of the three different ABO alleles.

Incomplete dominance supports the blending hypothesis.

Which of the following statements regarding genetic testing is false? Most human genetic diseases are treatable if caught early. Genetic testing before birth requires the collection of fetal cells. The screening of newborns can catch inherited disorders right after birth. Carrier testing helps determine whether a person carries a potentially harmful disorder.

Most human genetic diseases are treatable if caught early

Which of the following statements best explains why dominant alleles that cause lethal disorders are less common than recessive alleles that cause lethal disorders? The presence of a lethal dominant allele causes sterility. Most individuals carrying a lethal dominant allele have the disorder and die before they reproduce, whereas individuals carrying a lethal recessive allele are more likely to be healthy and reproduce. Lethal disorders caused by dominant alleles are usually more severe than lethal disorders caused by recessive alleles. Unlike lethal disorders caused by recessive alleles, lethal disorders caused by dominant alleles usually cause the death of the embryo.

Most individuals carrying a lethal dominant allele have the disorder and die before they reproduce, whereas individuals carrying a lethal recessive allele are more likely to be healthy and reproduce.

After reading the paragraphs below, answer the question that follows. During a summer study abroad program, you travelled to Austria to study genetics at the University of Vienna. While you were there, a momentous discovery was made: some of Gregor Mendel's original lab books and notes were found to be buried outside of the abbey where he lived. It just so happened that the professor you were working with obtained copies of these notes and enlisted your help to decipher them. You hired a translator to translate Mendel's notes from Czech to English, and using your knowledge of modern genetics (which Mendel did not have!) you were able to construct a partial Punnett square (shown below). Because the notebook was damaged from being buried for so long, this is the only information that you have regarding a cross that Mendel must have performed. Your professor has tasked you with figuring out more about this experiment. In pea plants, round peas are dominant (R) and shriveled peas are recessive (r) and yellow peas (shown as light gray in Punnett square) are dominant (Y) and green peas (dark gray) are recessive (y). Using this information and the partial Punnett square above, what were the phenotypes of the parental plants that were used in this cross by Mendel? Rryy and rrYy RRyy and rryy RrYy and RrYy Rryy and RrYy

Rryy and RrYy

You are looking at an unknown cell under a microscope that has 22 chromosomes plus two X chromosomes. Which of the following is the most likely identity of this cell? an egg from a human female an epithelial cell from a male chicken an eye cell from a female grasshopper a skin cell from a human female

an eye cell from a female grasshopper

Research since Mendel's time has established that the law of segregation of genes during gamete formation: is invalid. applies to all asexually reproducing organisms. applies to all sexually reproducing organisms. applies to all forms of life.

applies to all sexually reproducing organisms.

A person with AB blood illustrates the principle of incomplete dominance. codominance. polygenic inheritance. pleiotropy.

codominance

According to this figure, heterozygotes for this form of hypercholesterolemia suffer from the disease because they don't produce enough LDL receptors. don't produce any LDL receptors. produce an abnormally shaped LDL receptor. produce too many LDL receptors.

don't produce enough LDL receptors.

After reading the paragraph below, answer the question that follows. A man and his wife are having trouble having a baby. Using modern technologies, the woman's eggs are removed, fertilized with her husband's sperm, and implanted into her uterus. The procedure is successful, and the woman gives birth to a healthy baby boy. After a while, though, they discover that their son is colorblind and has blood type O. The woman claims that the child can't be theirs since she has blood type A and her husband has type B. Also, neither parent is colorblind, although one grandparent (the woman's father) is also colorblind. As a genetic counselor, you would explain to the parents that the eggs must have been accidentally switched, since the baby's blood type has to match one of his parents. it is possible for the baby to have type O blood, since type O is inherited through a dominant allele. each parent could have contributed one recessive allele, resulting in type O blood. the eggs must have been accidentally switched, since a type A parent and a type B parent can have any type children except O.

each parent could have contributed one recessive allele, resulting in type O blood.

The individual features of all organisms are the result of the environment and individual needs. genetics. genetics and the environment. the environment.

genetics and the environment.

A carrier of a genetic disorder who does not show symptoms is most likely to be ________ to transmit it to offspring. heterozygous for the trait and able homozygous for the trait and able heterozygous for the trait and unable homozygous for the trait and unable

heterozygous for the trait and able

Which of the following is an example of incomplete dominance in humans? albinism ABO blood groups skin color hypercholesterolemia

hypercholesterolemia

All the offspring of a cross between a red-flowered plant and a white-flowered plant have pink flowers. This means that the allele for red flowers is ________ to the allele for white flowers. incompletely dominant dominant codominant recessive

incompletely dominant

Most people afflicted with recessive disorders are born to parents who were both affected by the disease. slightly affected by the disease, showing some but not all of the symptoms. subjected to some environmental toxin that caused the disease in their children. not affected at all by the disease.

not affected at all by the disease.

Most genetic disorders of humans are caused by multiple alleles. a mutation that occurs in the egg, sperm, or zygote. recessive alleles. dominant alleles.

recessive alleles