Mendelian Genetics

X-linked conditions are more common in men than in women because A) the genes associated with the x-linked conditions are linked x chromosome, which determines maleness B) men need to inherit only one copy of the recessive allele for the condition to be fully expressed. C) women simply do not develop the disease regardless of their genetic composition D) the sex chromosomes are more active in men than in women

B; men need to inherit only one copy of the recessive allele for the condition to be fully expressed.

Based on the data in table 1, which of the following best explains why there are no individuals with constricted pods in the F1 generation? A) Inflated pod shape is dominant to constricted pod shape B) The inflated-pod offspring in the F1 generation are homozygous C) Constricted pod shape typically arises from a new mutation in the F1 generation D) The constricted-pod offspring are carriers for the inflated pod shape allele

A; Inflated pod shape is dominant to constricted pod shape

In table II, the F1 offspring of the cross between broad=leaved, white-flowered plants with narrow-leaved, purple-flowered plants have a phenotype that differs from either parent. However, many test cross offspring have the same phenotype as one of the two plants in the parental cross, but relatively few test cross offspring have the same phenotype as the F1 offspring. which of the following best explains the observation? A) Recombination between the leaf-shape and flower color genes resulted in chromosomes carrying a dominant allele of both genes B) Recombination between the broad and narrow alleles of the leaf shape gene resulted in chromosomes carrying three different alleles at the same genetic locus. C) Independent assortment of homologous chromosomes resulted in the combinations of alleles present in the parental generation. D) The computer model cannot capture the possible assortment of gametes when multiple genes are considered.

A; Recombination between the leaf-shape and flower-color genes resulted in chromosomes carrying a dominant allele of both genes

In the following human pedigree, square represent males, circles represent females, and shaded symbols indicate individuals affected with a disorder. One of the affected males from the third generation had a child with a female who is a carrier. For the pedigree shown above, which of the following best expresses the probability that the couple's first son will be affected with the disorder? A) 25% B) 50% C) 75% D) 100%

B; 50%

In Drosophila melanogaster the allele for wild-type body color (B) is dominant to the recessive allele for black body color (b). Similarly, the allele for wild type wing shape (V) is dominant to the recessive allele for vestigial wings phenotype (v). In the cross diagrammed above, the expected and observed results are shown. Which of the following best explains the observed results of the cross? (A) The alleles for body color and wing shape assort independently, as predicted by Mendel's laws. (B) The genes for body color and wing shape are located close to each other on the same chromosome. (C) The traits of body color show complete dominance over the traits of wing shape. (D)The observed variations in body color and wing shape are detectable in males but not in females.

B; The genes for body color and wing shape are located close to each other on the same chromosome.

Which of the following provides the best justification for an assumption that might have been used in the computer simulation (Table II)? A) The broad allele is recessive to the narrow allele because broad leaves appear in every generation. B) The purple allele is dominant to the white allele because all the offspring from the cross of purple-flowered and white-flowered plants had purple flowers. C) The narrow allele is codominant with the purple allele because the purple-flower trait and the narrow-leaf trait segregate together. D) The white allele is dominant to both the broad narrow alleles because plants with either type of leaf shape can have white flowers.

B; The purple allele is dominant to the white allele because all the offspring from the cross of purple-flowered and white-flowered plants had purple flowers.

A genetic counselor is consulted by a young man who is worried about developing Huntington's disease, an inherited disorder caused by a dominant allele of a single gene. The young man explains that his cousin was recently diagnosed with Huntington's disease, and the news has caused him to consider his own risk of developing the disorder. Which of the following questions will best help the genetic counselor to evaluate the risk of the young man developing Huntington's disease and transmitting it to his children? A) Were you and your cousins born in the same geographical area? B) Were your parents or grandparents ever diagnosed with Huntington's disease? C) Were you in physical contact with a person diagnosed with Huntington's disease? D) Were you exposed to substances that are suspected of being mutagens?

B; Were your parents or grandparents ever diagnosed with Huntington's disease?

A man with high cholesterol levels is about to marry a woman whose total cholesterol levels are also higher than average. A physician has suggested they get tested for the HC (high blood cholesterol) allele. Which of the following is a valid ethical question concerning the test? (A) How important are the results of the test to the couple's health, since they already know they have HC? (B) How can they eliminate the allele for HC from their cells? (C) If both have the allele for HC, should an insurance company raise their rates because of the results of the test? (D) What cures are available for HC other than dietary changes and exercise?

C; If both have the allele for HC, should an insurance company raise their rates because of the results of the test?

Gregor Mendel's pioneering genetic experiments with pea plants occurred before the discovery of the structure and function A) Pea color and pea shape display independent inheritance patterns. B) Offspring of a given cross show all possible combinations of traits in equal proportions. C) Most offspring of a given cross have a combination of traits that is identical to that of either one parent or the other. D) Recessive phenotypes can skip a generation, showing up only in the parental and F2 generations.

C; Most offspring of a given cross have a combination of traits that is identical to that of either one parent or the other.

The pedigree below shows the inheritance of a dominant allele of a gene in a family over several generation. Circles represent females and squares represent males. Shaded symbols indicate individuals carrying the allele. The pedigree suggest that the gene is on a nuclear chromosome, and not on a mitochondrial DNA, because A) mitochondrial genes are not heritable B) mitochondrial mutations cannot produce dominant traits C) maternal mitochondrial mutations are inherited by all of a mother's offspring D) mitochondrial DNA is circular, whereas chromosomal DNA is linear

C; maternal mitochondrial mutations are inherited by all of a mother's offspring

In Table I, the ratio of phenotypes in the offspring from the test cross with F1 plants that had purple flowers and inflated pods suggests that the gene for flower color and pod shape are located (A) close together on the same autosome (B) on the X chromosome (C) on different chromosomes (D) on a mitochondrial chromosome

C; on different chromosomes

Which of the following is supported by the data? A. The alleles for gray body and long wings are dominant B. The alleles for gray body and long wings are recessive C. Genes for the two traits are located on two different chromosomes and independent assortment occurred D. Genes for the two traits are located close together on the same chromosome and crossing over occurred between the two gene loci

D; Genes for the two traits are located close together on the same chromosome and crossing over occurred between the two gene loci

Eye pigment in a particular strain of fly is determined by two genes. An autosomal gene that controls the color of the pigments in the eye has two alleles: a dominant allele (R) that results in red eyes and a recessive allele (r) that results in sepia eyes. A sex-linked gene that controls the expression of the colored pigments also has two alleles: a dominant allele (T) that allows for expression of the colored pigments and a recessive allele (t) that does not allow for expression of the colored pigments. Individuals without a T allele have white eyes regardless of the alleles of other eye-color genes. Which of the following represents a cross between a white-eyed female and a red-eyed male? A) Tt XRXR x tt XrY B) Tt XrXr x tt XRY C) RR XTXT x Rr XTY D) Rr XtXt x Rr XTY

D; Rr XtXt x Rr XTY

The data above represents the results of three different crosses involving the inheritance of a gene that determines whether a certain organism is blue or white. Which of the following best explains the mechanism of inheritance of the gene? A) The allele for white is an autosomal dominant allele because 1:1 phenotype ratio of blue to white among both sexes is observed in cross 3. B) The all for blue is an autosomal dominant allele because an approximate 3:1 phenotype ratio of blue to white is observed in cross 1 C) The allele for white is an x-linked dominant allele because no white females are produced in cross 1. D) The allele for blue is an x-linked dominant allele because there are no blue male offspring in cross 2

D; The allele for blue is an x-linked dominant allele because there are no blue male offspring in cross 2

Which of the following is the most likely explanation of the results A) The two genes are located on two different chromosomes B) The two genes are sex-linked C) The two genes are located on mitochondrial DNA D) The two genes are linked on an autosome

D; The two genes are linked on an autosome

Hydrangea macrophylla is a species of plant with blue or pink flowers. Flower color in hydrangea macrophylla plants is thought to be determined primarily by soil conditions rather than inherited differences. Which of the following will provide the most direct evidence that flower color is due primarily to soil conditions? a) comparing DNA sequence information for Hydrangea macrophylla to DNA sequence information for a different species of flowering plant b) performing a genetic cross between a pink flowered plant and a blue flowered plant and then determining the ratio of phenotypes in the offspring c) growing cuttings from the same Hydrangea macrophylla plant under controlled conditions that vary only with regard to soil pH d) analyzing fossilized remains of an ancestral species that grew in geographic areas similar to the habitats of modern Hydrangea macrophylla.

c; growing cuttings from the same Hydrangea macrophylla plant under controlled conditions that vary only with regard to soil pH