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Biology & Life Science
Q:
What two terms apply to the fusion of cultured human and mouse cells that produces cell lines that are useful in assigning a gene to a particular human chromosome?
A) forward and reverse
B) lod score and pod score
C) heterokaryon and synkaryon
D) single and double
E) positive and negative
Q:
The phenomenon in which one crossover decreases the likelihood of crossovers in nearby regions is called
A) chiasma.
B) negative interference.
C) reciprocal genetic exchange.
D) positive interference.
E) mitotic recombination.
Q:
Assume that a cross is made between AaBb and aabb plants and that the offspring occur in the following numbers: 106 AaBb, 48 Aabb, 52 aaBb, 94 aabb. These results are consistent with the following circumstance:
A) sex-linked inheritance with 30% crossing over.
B) linkage with 50% crossing over.
C) linkage with approximately 33 map units between the two gene loci.
D) independent assortment.
E) 100% recombination.
Q:
Assume that a cross is made between AaBb and aabb plants and that all the offspring are either AaBb or aabb. These results are consistent with the following circumstance:
A) complete linkage.
B) alternation of generations.
C) codominance.
D) incomplete dominance.
E) hemizygosity.
Q:
Assume that a cross is made between AaBb and aabb plants and that the offspring fall into approximately equal numbers of the following groups: AaBb, Aabb, aaBb, aabb. These results are consistent with the following circumstance:
A) independent assortment.
B) alternation of generations.
C) complete linkage.
D) incomplete dominance.
E) hemizygosity.
Q:
What term is applied when two genes fail to assort independently, that is, they tend to segregate together during gamete formation?
A) discontinuous inheritance
B) Mendelian inheritance
C) linkage
D) tetrad analysis
E) dominance and/or recessiveness
Q:
Mendel predicted that some genes will be carried in the same chromosome.
Q:
Exchanges occur between homologous chromosomes, but never between sister chromatids.
Q:
Restriction fragment length polymorphisms (RFLPs), microsatellites, and single-nucleotide polymorphisms (SNPs) were used by Morgan and Sturtevant to discover linkage in Drosophila.
Q:
Positive interference occurs when a crossover in one region of a chromosome reduces crossovers in nearby regions.
Q:
Linkage (viewed from results of typical crosses) always occurs when two loci are on the same chromosome.
Q:
The cross GE/ge x ge/ge produces the following progeny: GE/ge 404; ge/ge 396; gE/ge 97; Ge/ge 103. From these data one can conclude that there are 20 map units between the G and E loci.
Q:
The cross GE/ge x ge/ge produces the following progeny: GE/ge 404; ge/ge 396; gE/ge 97; Ge/ge 103. From these data one can conclude that the recombinant progeny are gE/ge and Ge/ge.
Q:
The cross GE/ge x ge/ge produces the following progeny: GE/ge 404; ge/ge 396; gE/ge 97; Ge/ge 103. From these data one can conclude that the G and E loci assort independently.
Q:
If two gene loci are on nonhomologous chromosomes, genes at these loci are expected to assort independently.
Q:
Sister chromatid exchanges increase in frequency in the presence of X-rays, certain viruses, ultraviolet light, and certain chemical mutagens. In what autosomal recessive disorder is there known to be an increase in sister chromatid exchanges?
Q:
What advantage does BrdU (bromodeoxyuridine) have in the study of chromosome structure and recombination?
Q:
Two lines of work indicated that crossing over actually involves breakage and reunion of chromatid material. What organisms were involved, and who did the work?
Q:
What are two commonly used DNA landmarks for mapping human genes?
Q:
The term expressivity defines the percentage of individuals who show at least some degree of expression of a mutant genotype.
Q:
Genomic anticipation refers to observations that a genetic disorder occurs at an earlier age in successive generations, whereas genetic imprinting occurs when gene expression varies depending on parental origin.
Q:
Genomic imprinting occurs when one allele converts another.
Q:
Expressivity is the term used to describe the balanced genetic output from a hemizygous condition.
Q:
Penetrance specifically refers to the expression of lethal genes in heterozygotes.
Q:
A conditional mutant is one whose expression is influenced by some environmental condition.
Q:
One result of X-linkage is a crisscross pattern of inheritance in which sons express recessive genes of their fathers and daughters express recessive genes of their mothers.
Q:
Pattern baldness and hen/cock feathering in fowl are examples of X-linked inheritance.
Q:
Sex-limited inheritance is the same as sex-linked inheritance.
Q:
Hemizygosity is the term one uses to describe the state of a gene that has no allele on the opposing chromosome.
Q:
Alleles that are masked by an epistatic locus are said to be hypostatic to the genes at that locus.
Q:
A typical epistatic ratio is 9:3:4.
Q:
The ABO blood group locus in humans provides an example of epistasis.
Q:
With multiple alleles, there can be more than two genetic alternatives for a given locus.
Q:
With both incomplete dominance and codominance, one expects heterozygous and homozygous classes to be phenotypically identical.
Q:
A 9:7 ratio indicates incomplete dominance.
Q:
Assume that a mutation occurs in the gene responsible for the production of hexosaminidase A, such that only about 50% of the enzyme activity is found in the heterozygote compared with a homozygous normal individual. If heterozygotes are phenotypically normal, we would say that the mutant allele is recessive to its normal allele.
Q:
"Gain of function" mutations are generally dominant since one copy in a diploid organism is sufficient to alter the normal phenotype.
Q:
Can females display pattern baldness?
Q:
What distinguishes sex-limited from sex-influenced inheritance?
Q:
Provide an example of sex-influenced inheritance.
Q:
Pattern baldness is determined by a single autosomal gene pair. When females are homozygous for this gene pair, can they show pattern baldness?
Q:
State a significant difference between X-linked and sex-influenced inheritance.
Q:
The genes for zeste eyes and forked bristles are located on the X chromosome in Drosophila melanogaster. Both genes are recessive. A cross is made between a zeste-eyed female and a forked-bristled male.
a) If 200 offspring from this cross were obtained, present the expected number, sex, genotype, and phenotype in each class of the F1.
b) If the F1 offspring were crossed to produce 800 flies of an F2 generation, present the expected number, sex, and phenotype in each class. Assume no crossing over.
Q:
The accompanying figure is a pedigree of a fairly common human hereditary trait in which the boxes represent males and the circles represent females. Shading symbolizes the abnormal phenotype. Given that one gene pair is involved:
a) Is the inheritance pattern X-linked or autosomal, recessive or dominant?
b) Give the genotype of each individual in the pedigree. If more than one genotypic possibility exists, present all possible alternatives.
Q:
If an X-linked disorder is lethal to the affected individual prior to the age at which one reaches reproductive maturation, the lethality will be expressed only in males. Why is
this so?
Q:
A cross was made between homozygous wild-type female Drosophila and yellow-bodied male Drosophila. All of the resulting offspring were phenotypically wild type. Offspring of the F2 generation had the following phenotypes: Based on this information:
a) Is the mutant gene for yellow body behaving as a recessive or dominant?
b) Is the yellow locus on an autosome or on the X chromosome?
Q:
The enzyme glucose-6-phosphate dehydrogenase deficiency (G6PD) is inherited as a recessive gene on the X chromosome in humans. A phenotypically normal woman (whose father had G6PD) is married to a normal man.
a) What fraction of their sons would be expected to have G6PD?
b) If the husband had G6PD, would it make a difference in your answer in part (a)?
Q:
Two forms of hemophilia are determined by genes on the X chromosome in humans. Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man. What is the probability that their first daughter will have hemophilia?
Q:
Two forms of hemophilia are determined by genes on the X chromosome in humans. Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man. What is the probability that their first son will have hemophilia?
Q:
The white-eye gene in Drosophila is recessive and sex-linked. Assume that a white-eyed female is mated to a wild-type male. What would be the phenotypes of the offspring?
Q:
Name three modes of inheritance that are influenced by the sex of individuals.
Q:
Regarding the ABO blood group system in humans, if an individual is genetically IBi and yet expresses the O blood type, which genotype is it likely to have?
Q:
A particular cross gives a modified dihybrid ratio of 9:7. What phenotypic ratio would you expect in a testcross of the fully heterozygous F1 crossed with the fully recessive type? Diagram the testcross using A,a,B,b as symbol sets.
Q:
Many of the color varieties of summer squash are determined by several interacting loci:
AA or Aa gives white, aaBB or aaBb gives yellow, and aabb produces green. Crosses among heterozygotes give a 12:3:1 ratio. What type of gene interaction would account for these results?
Q:
Comb shape in chickens represents one of the classic examples of gene interaction. Two gene pairs interact to influence the shape of the comb. The genes for rose comb (R) and pea comb (P) together produce walnut comb. The fully homozygous recessive condition (rrpp) produces the single comb. Assume that a rose-comb chicken is crossed with a walnut-comb chicken and the following offspring are produced: 17 walnut, 16 rose, 7 pea, 6 single.
a) What are the probable genotypes of the parents?
b) Give the genotypes of each of the offspring classes.
Q:
Assume that a dihybrid F2 ratio, resulting from epistasis, was 15:1. If a double heterozygote was crossed with the fully recessive type, what phenotypic ratio is expected among the offspring?
Q:
Assume that a dihybrid F2 ratio, resulting from epistasis, was 9:3:4. If a double heterozygote was crossed with the fully recessive type, what phenotypic ratio is expected among the offspring?
Q:
Which types of ratios are likely to occur in crosses (F2) when one is dealing with two interacting, epistatic gene pairs?
Q:
Many of the color varieties of summer squash are determined by several interacting loci: AA or Aa gives white, aaBB or aaBb gives yellow, and aabb produces green. Assume that two fully heterozygous plants are crossed. Give the phenotypes (with frequencies) of the offspring.
Q:
The following F2 results occur from a typical dihybrid cross:
purple: A_B_ 9/16
white: aaB_ 3/16
white: A_bb 3/16
white: aabb 1/1
If a double heterozygote (AaBb) is crossed with a fully recessive organism (aabb), what phenotypic ratio is expected in the offspring?
Q:
What is meant by the term epistasis? Distinguish between epistasis and dominance. Do not use examples in answering this question.
Q:
In the mouse, gene A allows pigmentation to be deposited in the individual coat hairs; its allele a prevents such deposition of pigment, resulting in an albino. Gene B gives agouti (wild-type fur); its allele b gives black fur.
a) Diagram the cross between a doubly heterozygous agouti mouse mated with a doubly homozygous recessive white mouse.
b) What would be the expected phenotypic ratio in the progeny?
Q:
A mutant gene that produces brown eyes (bw) is located on chromosome #2 of Drosophila melanogaster, whereas a mutant gene producing bright red eyes, scarlet (st), is located on chromosome #3. Phenotypically, wild-type flies (with dull red eyes), whose mothers had brown eyes and whose fathers had scarlet eyes, were mated. The 800 offspring possessed the following phenotypes: wild type (dull red), white, scarlet (bright red), and brown. Most of the 800 offspring had wild-type eyes, whereas those with white eyes were the least frequent.
a) Using standard symbolism, diagram the cross from the P generation and the F1 generation. Be certain to provide the alleles of the mutant genes.
b) From the information presented above, how many white-eyed flies would you expect in the F2 generation?
Q:
In a mating between individuals with the genotypes IAIB x ii, what percentage of the offspring are expected to have the O blood type?
Q:
In a mating between individuals with the genotypes IAi x ii, what percentage of the offspring are expected to have the O blood type?
Q:
In mice, there is a set of multiple alleles of a gene for coat color. Four of those alleles are as follows:
C = full color (wild)
cch = chinchilla
cd= dilution
c = albino
Given that the gene locus is not sex-linked and that each allele is dominant to those lower in the list, diagram the crosses indicated below and give the phenotypic ratios expected from each.
a) wild (heterozygous for dilution) x chinchilla (heterozygous for albino)
b) chinchilla (heterozygous for albino) x albino
Q:
The following coat colors are known to be determined by alleles at one locus in horses:
palomino = golden coat with lighter mane and tail
cremello = almost white
chestnut = brown
The following table gives ratios obtained in matings of the above varieties: a) Assign gene symbols for the genetic control of coat color on the basis of these data.
b) Diagram the last two matings.
Q:
The trait for medium-sized leaves in iris is determined by the genetic condition PP'. Plants with large leaves are PP, whereas plants with small leaves are P'P'. The trait for red flowers is controlled by the genes RR, pink by RR', and white by R'R'. A cross is made between two plants each with medium-sized leaves and pink flowers. If they produce 320 seedlings, what would be the expected phenotypes, and in what numbers would they be expected? Assume no linkage.
Q:
The trait of medium-sized leaves in iris is determined by the genetic condition PP'. Plants with large leaves are PP, whereas plants with small leaves are P'P'. A cross is made between two plants each with medium-sized leaves. If they produce 80 seedlings, what would be the expected phenotypes, and in what numbers would they be expected? What is the term for this allelic relationship?
Q:
Assume that a dihybrid cross is made in which the genes' loci are autosomal, independently assorting, and incompletely dominant. How many different phenotypes are expected in the offspring?
Q:
Assume that a cross is made between two organisms that are both heterozygous for a gene that shows incomplete dominance. What phenotypic and genotypic ratios are expected in the offspring?
Q:
Assume that a dihybrid cross (AaBb x AaBb) is made in which the gene loci are autosomal, independently assorting, and incompletely dominant. What phenotypic ratio would you expect from such a cross? Just provide the ratio, not the phenotypes.
Q:
How many different alleles can a gene have?
Q:
Because of the mechanism of sex determination, males of many species can be neither homozygous nor heterozygous. Such males are said to be ________.
A) dominant
B) hemizygous
C) recessive
D) complementary
E) None of the answers listed are correct.
Q:
With which of the following would hemizygosity most likely be associated?
A) codominance
B) incomplete dominance
C) trihybrid crosses
D) X-linked inheritance
E) sex-limited inheritance
Q:
Multiple mutations that are found to be present in a single gene are said to belong to the same ________ group.
A) phenotypic
B) allelic
C) transfer
D) complementation
E) expression
Q:
Typical ratios resulting from epistatic interactions in dihybrid crosses would be ________.
A) 9:3:3:1, 1:2:1
B) 1:1:1:1, 1:4:6:4:1
C) 9:3:4, 9:7
D) 1:2:2:4:1:2:1:2:1, 1:2:1
E) 3:1, 1:1
Q:
A condition in which one gene pair masks the expression of a nonallelic gene pair is called ________.
A) codominance
B) epistasis
C) dominance
D) recessiveness
E) additive alleles
Q:
What term is used to express the idea that several genes exert influence over the same characteristic?
A) coextension
B) co-adhesion
C) terminal interaction
D) gene interaction
E) transformation
Q:
What would be a typical phenotypic monohybrid ratio in which a lethal allele is involved?
A) 2:1
B) 9:3:3:1
C) 6:2:3:1
D) 13:5
E) 3:1