Genetics exam test queries and
answers graded A+
One centiMorgan equals how many map units?
1000
50
100
1
10 - ANS✅✅1
In somatic-cell hybridization experiments to map the chromosomal location of human genes, a
human cell line is crossed to what other type of cell line? - ANS✅✅A rodent cell line
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? - ANS✅✅0
______functions relate recombination frequencies to positions of genetic loci on a chromosome -
ANS✅✅Mapping
Recombination hotspots in humans are - ANS✅✅often found near but not within active genes.
In a deletion mapping experiment, an individual homozygous for a recessive mutation in the gene to
be mapped is crossed to an individual heterozygous for a deletion and the resulting offspring are all
wild type. What is the most correct interpretation for these results? - ANS✅✅The gene is not
located within the deleted region.
The following testcross produces the progeny shown: Aa Bb x aa bb → 40 Aa Bb, 10 Aa bb, 10 aa Bb,
40 aa bb. What is the percent recombination between the A and B loci? - ANS✅✅20%
A three-point testcross is performed to obtain data for gene mapping. A coefficient of coincidence of
2.0 is obtained. A coefficient of coincidence of 2.0 means that - ANS✅✅twice the number of
double crossover progeny were obtained in the offspring compared to the number expected based
upon probability.
,Two genes have been both assigned to chromosome 12 by somatic-cell hybridization analysis.
However when lod-score analysis is performed, the genes appear to be assorting independently. The
most likely reason for the different results is that the - ANS✅✅two genes are far apart on
chromosome 12.
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? - ANS✅✅The haplotype will be disrupted, and some alleles will no
longer be in linkage disequilibrium in future times.
Which of the following best describes the difference between recombination rates in humans and
chimpanzees? - ANS✅✅In both chimpanzees and humans, there are recombination hotspots, but
the location of the hotspots often differ between the two species.
Interchromosomal recombination (recombination between genes on different chromosomes) occurs
where in mitosis and/or meiosis? - ANS✅✅Anaphase I of meiosis
Map distances based on recombination rates between distant genes often underestimate the true
physical distances between genes because - ANS✅✅some multiple crossovers go undetected.
The coefficient of coincidence among three genes is 0.8. What is the interference? - ANS✅✅0.2
The following testcross produces the progeny shown: Aa Bb x aa bb → 10 Aa Bb, 40 Aa bb, 40 aa Bb,
10 aa bb. What was the arrangement of the genes in the Aa Bb parent? - ANS✅✅repulsion
For single crossovers, the frequency of recombination is half the frequency of crossing over because
- ANS✅✅each crossover takes place between only two of the four chromatids of a homologous
pair.
Chromosome maps constructed using recombination frequencies are - ANS✅✅genetic maps.
A three-point testcross is often used to - ANS✅✅efficiently map genes
Linked genes occasionally switch from one homologous chromosome to the other through which
process? - ANS✅✅Crossing over
,A three-point testcross is - ANS✅✅testcross for three genes
The genotype AB/ab means that - ANS✅✅alleles A and B are on the same chromosome
The degree to which one crossover interferes with additional crossovers in the same region is the -
ANS✅✅interference
A two-strand double crossover between two linked genes produces what type of gametes? Assume
that both crossovers occur on the same two chromatids - ANS✅✅Nonrecombinant only
Single-nucleotide polymorphisms (SNPs) are - ANS✅✅positions where individuals vary at a single
DNA base
One map unit equals what percent recombination? - ANS✅✅1
A method for finding which human chromosome a gene may be located on that involves fusing
human cells with rodent cells such as mice cells is called what? - ANS✅✅Somatic-cell hybridization
Gametes that contain only the original combination of alleles present in the parents are called -
ANS✅✅Nonrecombinant
A particular set of linked alleles is called a - ANS✅✅haplotype
When one wild type allele and one mutant allele are found on each chromosome, the genes are said
to be in - ANS✅✅repulsion
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 doesn't produce the gene
product. What chromosome is the gene most likely located on? - ANS✅✅9
Gametes that contain new combination of alleles not present in the parents are called -
ANS✅✅recombinant gametes
, The ratio of the observed number of double crossovers to the expected number of double
crossovers is the - ANS✅✅coefficient of coincidence.
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? - ANS✅✅1/2
In a three-point cross, the double-crossover progeny can be identified because they - ANS✅✅are
the least numerous progeny.
Which of the following statements is FALSE? - ANS✅✅In humans, recombination rates are about
the same for males and females.
Linked genes are those that
are located close together on the same chromosome
code for traits involved in sex and reproduction
are located on more than one chromosome
code for the same phenotypic traits
code for linked steps in a biochemical pathway - ANS✅✅are located close together on the same
chromosome.
Consider the following cross: Aa Bb x aa bb. If these genes assort independently, what proportion of
the progeny will have genotype Aa Bb? - ANS✅✅1/4
The following testcross produces the progeny shown: Aa Bb x aa bb → 10 Aa Bb, 40Aa bb, 40 aa Bb,
10 aa bb. What is the percent recombination between the A and B loci? - ANS✅✅20%
The following testcross produces the progeny shown: Aa Bb x aa bb → 40 Aa Bb, 10 Aa bb, 10 aa Bb,
40 aa bb. What was the arrangement of the genes in the Aa Bb parent? - ANS✅✅Coupling
answers graded A+
One centiMorgan equals how many map units?
1000
50
100
1
10 - ANS✅✅1
In somatic-cell hybridization experiments to map the chromosomal location of human genes, a
human cell line is crossed to what other type of cell line? - ANS✅✅A rodent cell line
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? - ANS✅✅0
______functions relate recombination frequencies to positions of genetic loci on a chromosome -
ANS✅✅Mapping
Recombination hotspots in humans are - ANS✅✅often found near but not within active genes.
In a deletion mapping experiment, an individual homozygous for a recessive mutation in the gene to
be mapped is crossed to an individual heterozygous for a deletion and the resulting offspring are all
wild type. What is the most correct interpretation for these results? - ANS✅✅The gene is not
located within the deleted region.
The following testcross produces the progeny shown: Aa Bb x aa bb → 40 Aa Bb, 10 Aa bb, 10 aa Bb,
40 aa bb. What is the percent recombination between the A and B loci? - ANS✅✅20%
A three-point testcross is performed to obtain data for gene mapping. A coefficient of coincidence of
2.0 is obtained. A coefficient of coincidence of 2.0 means that - ANS✅✅twice the number of
double crossover progeny were obtained in the offspring compared to the number expected based
upon probability.
,Two genes have been both assigned to chromosome 12 by somatic-cell hybridization analysis.
However when lod-score analysis is performed, the genes appear to be assorting independently. The
most likely reason for the different results is that the - ANS✅✅two genes are far apart on
chromosome 12.
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? - ANS✅✅The haplotype will be disrupted, and some alleles will no
longer be in linkage disequilibrium in future times.
Which of the following best describes the difference between recombination rates in humans and
chimpanzees? - ANS✅✅In both chimpanzees and humans, there are recombination hotspots, but
the location of the hotspots often differ between the two species.
Interchromosomal recombination (recombination between genes on different chromosomes) occurs
where in mitosis and/or meiosis? - ANS✅✅Anaphase I of meiosis
Map distances based on recombination rates between distant genes often underestimate the true
physical distances between genes because - ANS✅✅some multiple crossovers go undetected.
The coefficient of coincidence among three genes is 0.8. What is the interference? - ANS✅✅0.2
The following testcross produces the progeny shown: Aa Bb x aa bb → 10 Aa Bb, 40 Aa bb, 40 aa Bb,
10 aa bb. What was the arrangement of the genes in the Aa Bb parent? - ANS✅✅repulsion
For single crossovers, the frequency of recombination is half the frequency of crossing over because
- ANS✅✅each crossover takes place between only two of the four chromatids of a homologous
pair.
Chromosome maps constructed using recombination frequencies are - ANS✅✅genetic maps.
A three-point testcross is often used to - ANS✅✅efficiently map genes
Linked genes occasionally switch from one homologous chromosome to the other through which
process? - ANS✅✅Crossing over
,A three-point testcross is - ANS✅✅testcross for three genes
The genotype AB/ab means that - ANS✅✅alleles A and B are on the same chromosome
The degree to which one crossover interferes with additional crossovers in the same region is the -
ANS✅✅interference
A two-strand double crossover between two linked genes produces what type of gametes? Assume
that both crossovers occur on the same two chromatids - ANS✅✅Nonrecombinant only
Single-nucleotide polymorphisms (SNPs) are - ANS✅✅positions where individuals vary at a single
DNA base
One map unit equals what percent recombination? - ANS✅✅1
A method for finding which human chromosome a gene may be located on that involves fusing
human cells with rodent cells such as mice cells is called what? - ANS✅✅Somatic-cell hybridization
Gametes that contain only the original combination of alleles present in the parents are called -
ANS✅✅Nonrecombinant
A particular set of linked alleles is called a - ANS✅✅haplotype
When one wild type allele and one mutant allele are found on each chromosome, the genes are said
to be in - ANS✅✅repulsion
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 doesn't produce the gene
product. What chromosome is the gene most likely located on? - ANS✅✅9
Gametes that contain new combination of alleles not present in the parents are called -
ANS✅✅recombinant gametes
, The ratio of the observed number of double crossovers to the expected number of double
crossovers is the - ANS✅✅coefficient of coincidence.
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? - ANS✅✅1/2
In a three-point cross, the double-crossover progeny can be identified because they - ANS✅✅are
the least numerous progeny.
Which of the following statements is FALSE? - ANS✅✅In humans, recombination rates are about
the same for males and females.
Linked genes are those that
are located close together on the same chromosome
code for traits involved in sex and reproduction
are located on more than one chromosome
code for the same phenotypic traits
code for linked steps in a biochemical pathway - ANS✅✅are located close together on the same
chromosome.
Consider the following cross: Aa Bb x aa bb. If these genes assort independently, what proportion of
the progeny will have genotype Aa Bb? - ANS✅✅1/4
The following testcross produces the progeny shown: Aa Bb x aa bb → 10 Aa Bb, 40Aa bb, 40 aa Bb,
10 aa bb. What is the percent recombination between the A and B loci? - ANS✅✅20%
The following testcross produces the progeny shown: Aa Bb x aa bb → 40 Aa Bb, 10 Aa bb, 10 aa Bb,
40 aa bb. What was the arrangement of the genes in the Aa Bb parent? - ANS✅✅Coupling
