Learning Curve Ch. 7
Genes A and B are linked. When no crossing over occurs in an individual with genotype Aa Bb, what proportion of the gametes will be recombinant? a. 1 b. 1/2 c. 1/4 d. 0 e. the answer will vary depending upon how far apart the two genes are
0
The A and B loci are linked and 20 map units apart. Assume that a plant of AB/ab genotype is selfed (AB/ab x AB/ab). What proportion of the offspring will be of AB/AB genotype?
0.16 the probability of the sperm being AB is 0.4 and the probability of the egg being AB is also 0.4 so the probability of AB/AB zygote would be 0.4 x 0.4 = 0.16
One centiMorgan equals how many map units?
1
One map unit equals what percent recombination?
1
Genes A and B are linked. When a single crossover occurs in an individual with genotype Aa Bb, what proportion of the resulting gametes will be recombinant?
1/2
Consider the following cross: Aa Bb × aa bb. Assume loci A and B are completely linked with no crossing over. What proportion of the progeny will have genotype Aa Bb?
1/2 only two types of progeny (Aa Bb and aa bb) are produced in equal proportions
Consider the following cross: Aa Bb × aa bb. If these genes assort independently, what proportion of the progeny will have genotype Aa Bb?
1/4
Three linked genes in tomatoes are Normal (M) or mottled (m), smooth (P) or pubescent (p) epidermis, and purple (Aw) or green (aw) stem. Individuals heterozygous for all three genes were testcrossed by crossing to homozygous recessive parents and the resulting progeny are shown below: Which is the genetic distance between m and p?
8.0 m.u. the recombinants, which include the single crossovers and the double crossovers, are divided by the total progeny.
A chi-square test of _____ can be used to determine if linkage occurs between genes. a. independence b. equilibrium c. coupling d. linkage e. interference
a
During meiosis, linked genes will eventually end up in the same a. gamete b. centromere c. sister chromatids d. chromosome e. cross
a
If three genes (A B C) are linked (in that order), what kind of crossover event would NOT be observed? a. triple crossover b. double crossover c. single crossover between A and B d. single crossover between B and C
a
When one wild-type allele and one mutant allele are found on each chromosome, the genes are said to be in _____ configuration. a. repulsion b. equilibrium c. recombinant d. coupling e. association
a
When two wild-type alleles are found on one chromosome and two mutant alleles are found on the homologous chromosome, the alleles are said to be in ____configuration. a. coupling b. repulsion c. association d. recombinant e. equilibrium
a
Which of the following statements is FALSE? a. In humans, recombination rates are about the same for males and females. b. Recombination rates vary among different species. c. There is variation in recombination rates among human chromosomes. d. Recombination does not take place at similar rates in all parts of a chromosome in humans. e. Recombination rates are different for humans compared to mice and rats.
a
A coefficient of coincidence of 0.25 means that ______________________. a. there were four times as many parental progeny as recombinant progeny b. the frequency of observed double crossovers was 25% of the number expected if there was no interference c. the frequency of double crossovers was 25% d. there were four times as many single crossovers as double crossovers e. there were four times as many single crossovers in one region as there were in an adjacent region
b
A three-point cross is a a. cross involving three different parents. b. testcross for three genes. c. testcross with genes that are 3 map units apart. d. cross involving genes on three different chromosomes. e. testing for genetic differences among three individuals.
b
Deletion mapping uses chromosome deletions to determine a. how many genes are located on a particular chromosome. b. the chromosomal location of a gene. c. whether two mutations occur at the same locus or different loci. d. the map distances between genes on the same chromosome. e. whether an allele is dominant or recessive.
b
If the interference value for the double-crossover progeny from a three-point testcross is 0.3, what does that mean? a. that 30% of the expected double-crossover progeny will be observed b. that 70% of the expected double-crossover progeny will be observed c. that 70% of the expected double-crossover progeny will not be observed
b
The genotype AB/ab means that a. alleles A and b are on the same chromosome. b. alleles A and B are on the same chromosome. c. alleles at these two loci assort independently. d. alleles A and B are on different chromosomes. e. an individual of this genotype will produce four genetic types of gametes in equal frequencies.
b
Assume that a plant of AA BB genotype is crossed with a plant of aa bb genotype to produce Aa Bb offspring. What will be the genotypes of the recombinant gametes produced by the F1 plants? a. Aa and Bb b. AB and ab c. Ab and aB d. ab and aB e. AB and aB
c
Chromosome maps constructed using recombination frequencies are called _____ maps. a. physical b. coupling c. genetic d. crossing e. complementation
c
Gametes that contain new combinations of alleles not present in the parents are called _____ gametes. a. repulsion b. restricted c. recombinant d. haplotype e. nonrecombinant
c
In which parent can crossing over be detected? a. the homozygous recessive parent b. the homozygous dominant parent c. the heterozygous parent d. either homozygous recessive or heterozygous parent e. either the homozygous dominant or homozygous recessive parent
c
Since the location of recombination hotspots differ in humans and chimpanzees, recombination hotspot locations likely can be changed through evolution. Assume that some type of evolutionary event results in the establishment of a new human recombination hotspot in the middle of a particular haplotype on chromosome 4. Over time, what would likely be the effect of this new hotspot on the haplotype? a. The haplotype is likely to increase in size and include additional loci since the increased recombination will now produce more allelic combinations that will be inherited as a unit. b. The haplotype should remain in its original form over time. c. The haplotype will be disrupted and some alleles will no longer be in linkage disequilibrium in future times. d. The haplotype will immediately gain new alleles at other genetic loci, but through increased recombination it will eventually revert back to its original form. e. Several new haplotypes will be formed along the length of chromosome 4 by the increased rate of recombination.
c
What information does in situ hybridization provide? a. whether the protein is produced from a gene b. the size of a gene c. the chromosomal location of a gene d. the distance between two genes on a chromosome e. any mutations are found in a given gene
c
What is the method for finding which human chromosome a gene may be located on that involves fusing human cells with rodent cells, such as mice cells? a. lod score analysis b. haplotyping c. somatic-cell hybridization d. deletion mapping e. linkage analysis
c
Chromosome maps constructed using distances along the chromosome, often expressed as numbers of base pairs, are called _____ maps. a. genetic b. coupling c. complementation d. physical e. crossing
d
Harriet Creighton and Barbara McClintock obtained evidence that intrachromosomal recombination was the result of physical exchange between chromosomes by studying which organism? a. mice b. pea plants c. Drosophila d. corn (maize) e. humans
d
If an individual had the following genotypes at three linked loci (Aa bb Cc) and A b C were on one chromosome and a b c - on the other, which of the below chromosomes would likely be the most numerous outcome after meiosis? a. A b c b. a B C c. a B c d. A b C
d
In a three-point cross, the double-crossover progeny can be identified because they a. possess only mutant traits. b. are homozygous for all three loci. c. are the most numerous progeny. d. are the least numerous progeny. e. are the progeny with recessive phenotypes.
d
Linked genes occasionally switch from one homologous chromosome to the other through which process? a. linkage disequilibrium b. independent assortment c. interference d. crossing over e. separation of homologous chromosomes in anaphase II
d
The number of recombinant progeny divided by the total number of progeny is known as the _____ frequency. a. linkage b. interference c. linkage disequilibrium d. recombination e. coefficient of coincidence
d
What is the probability of double-recombinant progeny if the single recombination frequencies of progeny are 15% and 20%? a. 35% b. 15% c. 20% d. 3% e. 0%
d
Which of the following, if it occurs between two genes at meiosis, is expected to produce NO recombinants for these two genes? a. a three-strand double crossover b. a two-strand double crossover c. a single crossover d. a four-strand double crossover e. all of the above would be expected to produce recombinants
d
A three-point testcross is often used to a. determine whether mutations occur at the same or at different loci. b. determine if chromosome mutations are present. c. isolate mutations affecting a particular trait. d. do a complementation test. e. efficiently map genes.
e
Gametes that contain only the original combinations of alleles present in the parents are called _____ gametes. a. recombinant b. restricted c. haplotype d. repulsion e. nonrecombinant
e
If an individual was heterozygous at three linked loci (Aa Bb Cc) and A b C were on one chromosome and a B c - on the other, which of the below chromosomes would be a possible outcome after meiosis? Choose all that apply. a. A b C b. A B c c. a b c d. a B c e. All of the chromosomes above would be possible
e
In a somatic cell hybridization experiment, one cell line retained human chromosomes 4, 9, 15, and 21, a second cell line retained human chromosomes 2, 9, 13, and 21, and a third cell line retained human chromosomes 4, 13, 19, and 21. The first two cell lines produce the product of the gene whose chromosome location is being established, while the third cell line does not produce the gene product. Which chromosome is this gene most likely located on? a. 4 b. 15 c. 21 d. 13 e. 9
e
Physical-mapping methods do NOT rely on a. the location of linked genes on a chromosome. b. the sex of the organism. c. relative position of a gene on a chromosome. d. physical distances between genes. e. recombination frequencies.
e
Recombination hotspots in humans are a. usually found within active genes. b. only found on the X chromosome. c. found in males but not in females. d. located far from active genes. e. often found near but not within active genes.
e
What is an advantage of a three-point testcross over a two-point testcross? a. some double crossovers can be detected b. multiple three-point crosses are done to give a rough estimate of gene location c. the order of three genes can be determined from a single cross d. there is no advantage, a two-point testcross is the most efficient way to determine gene map distances e. a and c are both correct
e
True or False? Although recombination rates differ between species, the rates are the same within a species.
false
True or False? Genetic maps can pinpoint groups of linked genes on certain chromosomes.
false
True or False? Linked genes appear in a 9:3:3:1 ratio for any progeny generation.
false
True or False? Crossing over is essential in determining the order of genes in a three-point testcross.
true
True or False? Mendel's principle of independent assortment states that in an individual with the genotype AABB, the locus A will separate independently from the locus B.
true
