Chapter 9 Patterns of Inheritance

In humans, hemophilia is a sex-linked condition and normal blood clotting (H) is dominant to the condition of hemophilia (h). A woman with hemophilia marries a normal man. What are the probabilities of them having children with hemophilia and their sexes?

1/2 girls 1/2 boys 100% hemophilia for boys 0% girls have hemophilia but they are 100% carriers Xh Xh x XH Y

In summer squash, white fruit (Y) is dominant over yellow fruit (y), and disc shaped fruit (D) is dominant over sphere shaped fruit (d). A cross is made between a homozygous white, disc shaped squash and a yellow, sphere shaped squash. Show the genotypes for the parents and the genotypes and phenotypes for the F1 generation

1:1 yellow sphere shaped 1:1 white disc shaped

8. A testcross is A) a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest. B) a mating between an individual of unknown genotype and an individual heterozygous for the trait of interest. C) a mating between two individuals heterozygous for the trait of interest. D) a mating between two individuals of unknown genotype.

A) a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest.

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

A) heterozygous for the trait and able

1. Mendel conducted his most memorable experiments on A) peas. B) roses. C) guinea pigs. D) fruit flies.

A) peas.

4. 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? A) 3 black-eyed:1 orange-eyed B) 0 black-eyed:1 orange-eyed C) 1 black-eyed:3 orange-eyed D) 1 black-eyed:0 orange-eyed

B) 0 black-eyed:1 orange-eyed

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

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

12. Which of the following statements regarding prenatal testing is false? A) Results from chorionic villus sampling come faster than those from amniocentesis. B) Chorionic villus sampling is typically performed later in the pregnancy than amniocentesis. C) Ultrasound imaging has no known risk. D) Chorionic villus sampling and amniocentesis are usually reserved for pregnancies with higher than usual risks of complications

B) Chorionic villus sampling is typically performed later in the pregnancy than amniocentesis.

20. The sex chromosome complement of a normal human female is A) XO. B) XX. C) XY.

B) XX.

14. The expression of both alleles for a trait in a heterozygous individual illustrates A) incomplete dominance. B) codominance. C) pleiotropy. D) polygenic inheritance.

B) codominance.

15. A person with AB blood illustrates the principle of A) incomplete dominance. B) codominance. C) pleiotropy. D) polygenic inheritance.

B) codominance.

9. Dr. Smith's parents have normal hearing. However, Dr. Smith has an inherited form of deafness. Deafness is a recessive trait that is associated with the abnormal allele d. The normal allele at this locus, associated with normal hearing, is D. Dr. Smith's parents could have which of the following genotypes? A) DD and dd B) dd and dd C) Dd and Dd D) Dd and DD

C) Dd and Dd

11. Which of the following statements best explains why dominant alleles that cause lethal disorders are less common than recessive alleles that cause lethal disorders? A) Lethal disorders caused by dominant alleles are usually more severe than lethal disorders caused by recessive alleles. B) Unlike lethal disorders caused by recessive alleles, lethal disorders caused by dominant alleles usually cause the death of the embryo. C) 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. D) The presence of a lethal dominant allele causes sterility.

C) 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.

21. A colorblind woman marries a man who is not colorblind. All of their sons, but none of their daughters, are colorblind. Which of the following statements correctly explains these results? A) The gene for color vision is incompletely dominant to the gene for sex determination. B) The gene for color vision is codominant with the gene for sex determination. C) The gene for color vision is found on the X chromosome. D) The gene for color vision is found on the Y chromosome.

C) The gene for color vision is found on the X chromosome.

2. Which of the following statements regarding cross-breeding and hybridization is false? A) The offspring of two different varieties are called hybrids. B) The parental plants of a cross are the P generation. C) The hybrid offspring of a cross are the P1 generation. D) The hybrid offspring of an F1 cross are the F2 generation.

C) The hybrid offspring of a cross are the P1 generation.

13. 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. A) dominant B) codominant C) incompletely dominant D) recessive

C) incompletely dominant

18. Genes located close together on the same chromosomes are referred to as ________ genes and generally ________. A) linked; sort independently during meiosis B) homologous; are inherited together C) linked; do not sort independently during meiosis D) codependent; do not sort independently during meiosis

C) linked; do not sort independently during meiosis

19. What is the normal complement of sex chromosomes in a human male? A) two Y chromosomes B) two X chromosomes and one Y chromosome C) one X chromosome and one Y chromosome D) one Y chromosome

C) one X chromosome and one Y chromosome

7. ) Imagine that we mate two black Labrador dogs with normal vision and find that three of the puppies are like the parents, but one puppy is chocolate with normal vision and another is black with PRA (progressive retinal atrophy, a serious disease of vision). We can conclude that A) both of the parents are homozygous for both traits. B) the same alleles that control coat color can also cause PRA. C) the alleles for color and vision segregate independently during gamete formation. D) the alleles for color and vision segregate dependently during gamete formation.

C) the alleles for color and vision segregate independently during gamete formation.

6. ) The phenotypic ratio resulting from a dihybrid cross of two heterozygote individuals showing independent assortment is expected to be A) 1:2:1 B) 3:1 C) 9:1:1:3 D) 9:3:3:1

D) 9:3:3:1

17. The individual features of all organisms are the result of A) genetics. B) the environment. C) the environment and individual needs. D) genetics and the environment.

D) genetics and the environment.

16. Which of the following terms refers to a situation where a single phenotypic character is determined by the additive effects of two or more genes? A) incomplete dominance B) codominance C) pleiotropy D) polygenic inheritance

D) polygenic inheritance

5. ) The alleles of a gene are found at ________ chromosomes. A) the same locus on nonhomologous B) different loci on homologous C) different loci on nonhomologous D) the same locus on homologous

D) the same locus on homologous