Unit 5 Genetics
A blue-flowered African violet of unknown ancestry self-pollinated and produced 50 seeds. These seeds germinate and grow into flowering plants. Of these plants, 36 produce blue flowers and 14 produce pink flowers. What is the best explanation for the pink-flowered offspring? A) Pink flower color is a trait recessive to blue flower color. B) A previous generation of the blue-flowered parent must have included 50 percent pink-flowered plants. C) Pink flower color is the result of somatic mutations in the flower color gene. D) Blue flowers are incompletely dominant to pink flowers.
A) Pink flower color is a trait recessive to blue flower color.
A certain species of plant has four unlinked genetic loci, W, X, Y, and Z. Each genetic locus has one dominant allele and one recessive allele. For a plant with the genotypes WwXxYyZz, what is the probability that the plant will produce a gamete with a hybrid genotype Wxyz? A) 1/16 B) 1/4 C) 1/2 D) 1/8 E) Not enough information is given in the problem
A) 1/16
Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of the cross BbTt x Bbtt will have black fur and long tails? A) 3/8 B) 9/16 C) 1/2 D) 3/16 E) 1/16
A) 3/8
How many unique gametes could be produced through independent assortment by an individual with the genotype AABbCCDdEE? A) 4 B) 8 C) 64 D) 32 E) 16
A) 4
In Drosophila melanogaster the allele for wild-type tan body color (B) is dominant to the recessive allele for the black body color (b). Similarly, the allele for wild-type wing shape (V) is dominant to the recessive allele for vestigial wing 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 genes for body color and wing shape are located close to each other on the same chromosome. B) The alleles for body color and wing shape assort independently, as predicted by Medel's laws. C) The observed variations in the body color and wing shape are detectable in males but not females. D) The traits for body color show complete dominance over the traits for wing shape.
A) The genes for body color and wing shape are located close to each other on the same chromosome.
Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following? A) gaps left at the 5' end of the lagging strand because of the need for a 3' onto which nucleotides can attach B) DNA polymerase that cannot replicated the leading strand template to its 5' end C) the "no ends" of a circular chromosome D) the evolution of telomerase enzyme E) gaps left at the 3' end of the lagging strand because pf the need for a primer
A) gaps left at the 5' end of the lagging strand because of the need for a 3' onto which nucleotides can attach
A student in a biology class crossed a male Drosophila melanogaster having a gray body and long wings with a female D. melanogaster having a black body and apterous wings. The following distribution of traits was observed in the offspring. Phenotype Gray body, long wing 42 Black body, apterous wings 41 Gray body, apterous wings 9 Black body, long wings 8 Which of the following is supported by the data? A) Genes for the two traits area located close together on the same chromosome, and crossing over occurred between the two gene loci B) The alleles for gray body and long wings are recessive C) The alleles for gray body and long wings are dominant D) Genes for the two traits are located on two different chromosomes
A) genes for the two traits are located close together on the same choró some, and crossing over occurred between the two gene loci
Arctic foxes typically have a white coat in the winter. In summer, when there is no snow on the ground, the foxes typically have a darker coat. Which of the following is most likely responsible for the seasonal change in coat color? A) the decrease in the amount of daylight in winter causes a change in gene expression, which results in the codes rowing a lighter-appearing coat B) the diet of the foxes in summer lacks a particular nutrient, which causes the foxes to lose their white coat and grow a darker-colored coat C) competition for mates in the spring causes each fox to increase its cam ou flange with the environment by producing a darker-appearing coat D) the lower temperatures in winter denature the pigment molecules in the arctic fox coat, causing te coat to become lighter in color
A) the decrease in the amount of daylight in winter causes a change in gene expression, which results in the codes rowing a lighter-appearing coat
In a species that has five different alleles fro an gene at a particular locus, how many different alleles may e present in the somatic cells of one diploid individual? A) two B) four C) three D) five E) one
A) two
A child is born with blood type A to a mother with blood type B> The father must have which of the following blood types? A) AB or A or O B) Either AB or A C) Either AB or B D) AB only E) Either AB or O
B) Either AB or A
Which of the following best describes the parents in a test cross? A) Both individuals have an unknown phenotype. B) One individual has the dominant phenotype and the other has the recessive phenotype. C) Both individuals have the recessive phenotype. D) Both individuals have the dominant phenotype. E) Both individuals are heterozygous.
B) One individual has the dominant phenotype and the other has the recessive phenotype.
Hydrangea macrophylla is a species of plant with blue or pink flower. Flower color in Hydrangea macrophylla plants is thought to e determined primarily by soil conditions rather than by inherited differences. Which of the following will provide the most direct evidence that flower color in Hydrangea macrophylla 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) growing cuttings from the same Hydrangea macrophylla plant under controlled Cont ions that vary only with regard to soil pH C) performing a genetic cross between a pink-flowered plant and a blue-flowered plant and then deterring the ratio of phenotypes in the offspring D) analyzing fossilized remains of an ancestral species that grew in geographic areas similar to the habitat as of modern Hydrangea macrophylla
B) growing cuttings from the same Hydrangea macrophylla plant under controlled Cont ions that vary only with regard to soil pH
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? A) unwind the parental double helix B) join Okazaki fragments together C) stabilize the unwound parental DNA D) synthesize RNA nucleotides to make a primer E) catalyze the lengthening of telomeres
B) join Okazaki fragments together
The F1 offspring of Mendel's classic pea cross always looked like one of the two parental charities because A) the traits blended together during fertilization B) one phenotype was completely dominant over another C) each allele affected phenotypic expression D) different gees interacted to produce the parental phenotype E) no genes interacted to produce the parental phenotype
B) one phenotype was completely dominant over another
**ONLY THING DIFFERENT about karyotype is there is: XXY The diagram above depicts a karyotype of an individual human. Which of the following statements concerning the karyotype in the diagram is true? A) the diagram indicates a mechanism for increasing genetic diversity in subsequent generations B) the diagram illustrates the results of nondisjunction during gamete formation C) the diagram indicates Down syndrome, a genetic condition D) the diagram illustrates a genetic condition found in females
B) the diagram illustrates the results of nondisjunction during gamete formation
How many different genotypes are possible from the cross of AaBb x AaBb? A) 7 B) 16 C) 9 D) 4 E) 2
C) 9
Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine? A) 38 B) 31 C) 12 D) 24 E) It cannot be determined form the inforamtion provided
C) 12
Which of the following removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments? A) helicase B) DNA polymerase III C) DNA polymerase I D) primase E) ligase
C) DNA polymerase I
Two types of cholesterol transport proteins, low-density lipoproteins (LDL) and higher-density lipoproteins (HDL), bind to cholesterol and carry it through the bloodstream. Familial hyper cholesterol Emma (FH) is characterized by high cholesterol levels in the blood, which can lead to cardiovascular disease. FH is associated with a loss-of-function mutation of a gene that encodes LDL receptors in liver cells. Individuals who are heterozygous produce lower-than-normal amounts of the LDL receptors, and individuals who are homozygous for the mutant allele have no LDL receptors function. Individuals with FH can be treated with drugs that result in increased production of LDL receptors in liver cells. Which of the following best explains the observation that the drugs can effectively control blood cholesterol level in individuals who are heterozygous but are not effective in individuals homozygous for the mutant allele? A) the drugs prevent cholesterol from entering the liver cells in individuals who are heterozygous but not in individuals who are homozygous for the mutants allele B) the drugs repair the mutant allele by copying the wild-type allele C) there must be a least one copy of the wild-type LDL receptor allele to produce functional LDL receptor. D) Cholesterol molecules primarily bind to HDL receptors in individuals with FH
C) there must be a least one copy of the wild-type LDL receptor allele to produce functional LDL receptor.
In a particular variety of corn, kernel color is controlled by a single gene with two alleles. The dominant allele results in purple kernels, and the recessive allele results in yellow kernels. A single corn cob may contain hundreds of individual kernels, each of which is the result of a separate fertilization event. Which of the following would be the best prediction four the frequency of yellow kernels that result from a cross between two heterozygous plants? A) 75% B) 0% C) 50% D) 25%
D) 25%
In the following human pedigree, squares represent males, circles represent females, and shaded symbols indicate individual affect with the disorder. One of the affected males from the third generation has 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) 75% B) 100% C) 25% D) 50%
D) 50%
Which of the following can be diagnosed by examining a karyotype of an individual's white blood cells? A) Sickle cell anemia B) Cystic fibrosis C) Alzheimer's disease D) Down syndrome E) Duchesse muscular dystrophy
D) Down syndrome
Eye color in a particular strain of fly is influenced by one gene with two alleles: a dominant allele that results in red eyes and a recessive that results in sepia eyes. A red-eyed female from a true-breeding population is mated with a sepia-eyed male. The F1 offspring are all red-eyed. The F1 flies are allowed to interbreed, producing the following in the F2 generation. Females: 40 red eyes; 13 sepia eyes Males: 39 red eyes; 11 sepia eyes Which of the following best describes the likely mode of inheritance for the eye-color gene? A) The eye-color gene is likely autosomal because more females have sepia eyes than males do. B) The eye-color gene is likely sex-linked because males and females have similar phenotype ratios. C) The eye-color gene is likely sex-linked because males and females display both phenotypes. D) The eye-color gene is likely autosomal because males and females have similar phenotype ratios.
D) The eye-color gene is likely autosomal because males and females have similar phenotype ratios.
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 for a single gene. The young man explained 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 ever exposed to substances that are suspected of being mutagens? B) Were you in physical contact with a person diagnosed with Huntington's disease? C) Were you and your cousin both in the same geographical area? D) Were your parents or grandparents ever diagnosed with Huntington's disease?
D) Were your parents or grandparents ever diagnosed with Huntington's disease?
Coat color in mice is determined by genes at two loci. When black mice from a particular population mat,e they produce offspring in the following ratios: 9 black: 3 brown: 4 white. These results suggest that white coat color is expressed as a result of A) a sex-lined trait B) dominance C) incomplete dominance ce D) epistasis E) codomiance
D) epistasis
Cross 1: 60 blue males, 52 white males, 124 blue females. Cross 2: 108 white males, 115 blue females Cross 3: 48 blue males, 53 white males, 42 blue females, 49 white females The data above represent 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 the 1:1 phenotype ratio of blue to white among both sexes is observed in cross 3 B) the allele for blue is an autosomal dominant allele because an approximate 3:1 phenotype ration 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
A couple has 5 children, all sons. If the woman gives birth to a sixth child, what is the probability that the sixth child will be a son? A) 1/64 B) 1/5 C) 1/6 D) 5/6 E) 1/2
E) 1/2
In peas the trait for tall plants is dominant (T) and the trait for short plants is recessive (t). The trait for yellow seed color is dominant (Y) and the trait for green seed color is recessive (y). A cross between two plants results in 296 tall yellow plants and 104 tall green plants. Which of the following are most likely to be the genotypes of the parents? A) TtYy xTtYy B) TtYY x TtYy C) TTYY x TTYY D) TTYy x TTYy E) TtYy x TTYy
E) TtYy x TTYy
In humans, red-green color blindness is a sex-linked recessive trait. If a man and a woman produce a color-blind so, which of the following must be true? A) both parents carry the allele color blindness B) the father carries the allele for color blindness C) the father is color-blind D) neither parent carries the allele for color blindness E) the mother carries the allele for color blindness
E) the mother carries the allele for color blindness
