MMSC491 Exam 2
Exam Study Guide – Practice
Questions with Verified
Answers. GRADED A+. Latest
2026/2027 Update
The term phenotype can be applied to a wide range of manifestations. Which
of the following properties, if any, do not constitute a phenotypic
manifestation?
The number of digits a person has.
The transcriptome of a single T cell.
The sequence of a persons beta globin gene.
autistic behavior - Answer✔✔-The sequence of a persons beta globin gene.
Which, if any, of the following is incorrect? When used in human genetics,
the terms dominant and recessive apply equally to alleles and phenotypes.
dominant describes a phenotype that is manifested in the heterozygote, that is,
the phenotype is attributable to just a single allele.
recessive describes a phenotype that is manifest as a result of the combined
effects of both alleles at a locus.
the AB blood group is an example of a co-dominant phenotype. - Answer✔✔-
the terms dominant and recessive apply equally to alleles and phenotypes.
,With respect to autosomal recessive inheritance, which, if any, of the following
statements is incorrect?
Affected individuals normally have unaffected parents.
For unaffected parents who have a previously affected child, there is a 1 in 4
risk of having an affected child on each occasion that they produce a new child.
Heterozygotes are always asymptomatic carriers.
Some affected individuals have alleles with identical pathogenic mutations but
many have two different mutant alleles and are described as compound
heterozygotes. - Answer✔✔-Heterozygotes are always asymptomatic carriers.
With respect to X-chromosome inactivation in females, which, if any, of the
following statements is incorrect?
X-inactivation first occurs in the preimplantation female mammalian embryo.
One of the two X chromosomes in each diploid cell of a normal woman is
randomly selected to undergo X-inactivation and becomes highly condensed.
The process involves epigenetic silencing of each gene on one of the two X
chromosomes, either the maternal X chromosome or the paternal X
chromosome.
Once the decision is made to inactivate a paternal X or the maternal X in a cell,
all descendant cells will continue with that pattern of X-inactivation. -
Answer✔✔-The process involves epigenetic silencing of each gene on one of
the two X chromosomes, either the maternal X chromosome or the paternal X
chromosome.
With respect to X-linked recessive inheritance, which, if any, of the following
statements is false?
Males with just one mutant allele are affected because, lacking a second X
chromosome, they do not have a normal allele.
,Women are always asymptomatic.
The disorder is not transmitted from fathers to sons.
Each child born to a normal man and a carrier woman has a risk of 1in 4 of
being affected. - Answer✔✔-Women are always asymptomatic.
With respect to X-linked dominant inheritance, which, if any, of the following
statements is false?
There are significantly more affected females than males.
Each child born to an affected mother has a risk of 1 in 2 of being affected.
Each daughter born to an affected father has a risk of 1 in 2 of being affected.
Each boy born to an affected father has a negligible risk of being affected. -
Answer✔✔-Each daughter born to an affected father has a risk of 1 in 2 of
being affected.
With respect to mitochondrial inheritance, which, if any, of the following
statements is false?
Affected individuals can be of either sex.
Mitochondrial disorders are transmitted virtually exclusively through the
maternal line.
Both the sperm and the egg contribute mitochondrial DNA to the zygote,
however, the paternal mtDNA is destroyed in the early embryo.
Clinical variability is a common feature of mitochondrial DNA disorders. -
Answer✔✔-All of the statements are true
With respect to mosaicism, which, if any, of the following statements, is false?
Any person who has two or more cells that have a different genetic constitution
is a mosaic
, All women are genetic mosaics
Every person is a genetic mosaic.
Mosaicism is the inevitable consequence of germline mutations. - Answer✔✔-
Mosaicism is the inevitable consequence of germline mutations.
Purifying selection results in which of the following?
Removes harmful alleles from the population
Amplifies genes which can compensate for the loss of function mutant allele
Increases the frequency of a fitness conferring gene in the population
The process by which DNA is purified to carry out genetic testing. - Answer✔✔-
Removes harmful alleles from the population
List three examples of a single gene disorder where there is extremely limited
mutational heterogeneity and one example where different mutations in one
gene result in a wide range of different diseases. - Answer✔✔-Three examples
of a gene disorder where there is limited mutational heterogeneity are
Huntington's disease (late onset, single gene mutation), achondroplasia (single
nucleotide mutation in a single gene), and cystic fibrosis (recessive, but single
CFTR gene mutation). One example of a gene where different mutations in one
gene result in a wide range of different diseases is the lamin A/C gene in the
textbook, which shows that ten different diseases can arise from different
mutations in just one (LMNA) gene.
For some single gene disorders, some members of a family who have the same
genetic variants at the disease locus as strongly affected family members either
show a much milder phenotype or no disease symptoms. List five explanations
for why there can be a lack of penetrance or variable expressivity of a single
gene disorder. - Answer✔✔-1. Environmental factors can lead to different
expressions of genes based on the person and environment they live in.
Exam Study Guide – Practice
Questions with Verified
Answers. GRADED A+. Latest
2026/2027 Update
The term phenotype can be applied to a wide range of manifestations. Which
of the following properties, if any, do not constitute a phenotypic
manifestation?
The number of digits a person has.
The transcriptome of a single T cell.
The sequence of a persons beta globin gene.
autistic behavior - Answer✔✔-The sequence of a persons beta globin gene.
Which, if any, of the following is incorrect? When used in human genetics,
the terms dominant and recessive apply equally to alleles and phenotypes.
dominant describes a phenotype that is manifested in the heterozygote, that is,
the phenotype is attributable to just a single allele.
recessive describes a phenotype that is manifest as a result of the combined
effects of both alleles at a locus.
the AB blood group is an example of a co-dominant phenotype. - Answer✔✔-
the terms dominant and recessive apply equally to alleles and phenotypes.
,With respect to autosomal recessive inheritance, which, if any, of the following
statements is incorrect?
Affected individuals normally have unaffected parents.
For unaffected parents who have a previously affected child, there is a 1 in 4
risk of having an affected child on each occasion that they produce a new child.
Heterozygotes are always asymptomatic carriers.
Some affected individuals have alleles with identical pathogenic mutations but
many have two different mutant alleles and are described as compound
heterozygotes. - Answer✔✔-Heterozygotes are always asymptomatic carriers.
With respect to X-chromosome inactivation in females, which, if any, of the
following statements is incorrect?
X-inactivation first occurs in the preimplantation female mammalian embryo.
One of the two X chromosomes in each diploid cell of a normal woman is
randomly selected to undergo X-inactivation and becomes highly condensed.
The process involves epigenetic silencing of each gene on one of the two X
chromosomes, either the maternal X chromosome or the paternal X
chromosome.
Once the decision is made to inactivate a paternal X or the maternal X in a cell,
all descendant cells will continue with that pattern of X-inactivation. -
Answer✔✔-The process involves epigenetic silencing of each gene on one of
the two X chromosomes, either the maternal X chromosome or the paternal X
chromosome.
With respect to X-linked recessive inheritance, which, if any, of the following
statements is false?
Males with just one mutant allele are affected because, lacking a second X
chromosome, they do not have a normal allele.
,Women are always asymptomatic.
The disorder is not transmitted from fathers to sons.
Each child born to a normal man and a carrier woman has a risk of 1in 4 of
being affected. - Answer✔✔-Women are always asymptomatic.
With respect to X-linked dominant inheritance, which, if any, of the following
statements is false?
There are significantly more affected females than males.
Each child born to an affected mother has a risk of 1 in 2 of being affected.
Each daughter born to an affected father has a risk of 1 in 2 of being affected.
Each boy born to an affected father has a negligible risk of being affected. -
Answer✔✔-Each daughter born to an affected father has a risk of 1 in 2 of
being affected.
With respect to mitochondrial inheritance, which, if any, of the following
statements is false?
Affected individuals can be of either sex.
Mitochondrial disorders are transmitted virtually exclusively through the
maternal line.
Both the sperm and the egg contribute mitochondrial DNA to the zygote,
however, the paternal mtDNA is destroyed in the early embryo.
Clinical variability is a common feature of mitochondrial DNA disorders. -
Answer✔✔-All of the statements are true
With respect to mosaicism, which, if any, of the following statements, is false?
Any person who has two or more cells that have a different genetic constitution
is a mosaic
, All women are genetic mosaics
Every person is a genetic mosaic.
Mosaicism is the inevitable consequence of germline mutations. - Answer✔✔-
Mosaicism is the inevitable consequence of germline mutations.
Purifying selection results in which of the following?
Removes harmful alleles from the population
Amplifies genes which can compensate for the loss of function mutant allele
Increases the frequency of a fitness conferring gene in the population
The process by which DNA is purified to carry out genetic testing. - Answer✔✔-
Removes harmful alleles from the population
List three examples of a single gene disorder where there is extremely limited
mutational heterogeneity and one example where different mutations in one
gene result in a wide range of different diseases. - Answer✔✔-Three examples
of a gene disorder where there is limited mutational heterogeneity are
Huntington's disease (late onset, single gene mutation), achondroplasia (single
nucleotide mutation in a single gene), and cystic fibrosis (recessive, but single
CFTR gene mutation). One example of a gene where different mutations in one
gene result in a wide range of different diseases is the lamin A/C gene in the
textbook, which shows that ten different diseases can arise from different
mutations in just one (LMNA) gene.
For some single gene disorders, some members of a family who have the same
genetic variants at the disease locus as strongly affected family members either
show a much milder phenotype or no disease symptoms. List five explanations
for why there can be a lack of penetrance or variable expressivity of a single
gene disorder. - Answer✔✔-1. Environmental factors can lead to different
expressions of genes based on the person and environment they live in.
