Question 1

Which of the following is the molecular explanation for genetic anticipation?&#10;A) Mitochondrial mutations&#10;B) Heteroplasmy&#10;C) Trinucleotide repeat expansions&#10;D) Skewed X-inactivation&#10;E) Mutational selection

Accepted Answer

Trinucleotide repeat expansions can increase in size with each generation, leading to earlier onset and more severe symptoms in subsequent generations.

Question 2

When there is more than one mtDNA complement present in an individual,this is known as which of the following?&#10;A) Heteroplasmy&#10;B) Multiallelism&#10;C) Heterogeneity&#10;D) Pleiotropy&#10;E) Mitochondrial variance

Accepted Answer

Heteroplasmy is the presence of more than one mtDNA complement in an individual, which can lead to differences in mitochondrial function and disease susceptibility. Multiallelism refers to the existence of multiple alleles of a gene in a population, not specifically related to mtDNA. Heterogeneity refers to the presence of different characteristics or types within a population or sample. Pleiotropy refers to a single gene or mutation affecting multiple traits or phenotypes. Mitochondrial variance is not a commonly used term in genetics.

Question 3

Autosomal dominant inheritance for a mutation can usually be ruled out when which of the following is observed in a family?&#10;A) The disease skips a generation&#10;B) An affected child is born to unaffected parents&#10;C) Transmission from father to son&#10;D) The phenotype varies between affecteds in the family&#10;E) The parents of the proband are consanguineous

Accepted Answer

The parents of the proband are consanguineous

Question 4

Maternal uniparental disomy for chromosome 15 is associated with which phenotype?&#10;A) Prader-Willi syndrome&#10;B) Angelman syndrome&#10;C) Beckwith-Wiedemann syndrome&#10;D) Russell-Silver syndrome&#10;E) Myotonic dystrophy

Accepted Answer

Maternal uniparental disomy for chromosome 15 results in the loss of the paternal copy of this chromosome and duplication of the maternal copy. This is associated with the development of Prader-Willi syndrome, which is characterized by neonatal hypotonia, feeding difficulties in infancy, and later onset of hyperphagia leading to obesity, intellectual disability, and behavioral problems. Angelman syndrome, on the other hand, is caused by the loss of the maternal copy of chromosome 15, and is characterized by severe developmental delay, ataxia, seizures, and a happy, sociable disposition. Beckwith-Wiedemann syndrome and Russell-Silver syndrome are both associated with abnormalities of chromosome 11, while myotonic dystrophy is caused by a trinucleotide repeat expansion on chromosome 19.

Question 5

Which modification distinguishes the maternal from the paternal allele in imprinted regions?&#10;A) Phosphorylation&#10;B) Methylation&#10;C) Glycosylation&#10;D) Acetylation&#10;E) Glucosylation

Accepted Answer

The modification that distinguishes the maternal from the paternal allele in imprinted regions is methylation, which results in differential expression of genes depending on whether they are inherited from the mother or the father. Regions of DNA that are imprinted are marked by specific methyl groups that are added during gametogenesis and then maintained throughout development. These imprints are critical for normal embryonic and fetal development and can influence disease susceptibility later in life. None of the other modifications listed (phosphorylation, glycosylation, acetylation, or glucosylation) are known to play a role in genomic imprinting.

Question 6

When affected males pass a disorder to their daughters but not their sons,what is the likely pattern of inheritance?&#10;A) Autosomal dominant&#10;B) Autosomal recessive&#10;C) X-linked dominant&#10;D) X-linked recessive&#10;E) Y-linked

Accepted Answer

The disorder is likely X-linked dominant, meaning that affected males pass the disorder to all of their daughters, but not their sons, because males receive their X chromosome from their mother and their Y chromosome from their father. Daughters receive one X chromosome from each parent, so if the father has the disorder on his X chromosome, all of his daughters will inherit it. However, sons only receive one X chromosome from their mother and a Y chromosome from their father, so they cannot inherit an X-linked dominant disorder from their father.

Question 7

Which phenotype is associated with the same chromosome 15 region as Prader-Willi syndrome?&#10;A) Beckwith-Wiedemann syndrome&#10;B) Russell-Silver syndrome&#10;C) Angelman syndrome&#10;D) Tuberous sclerosis&#10;E) Turner syndrome

Accepted Answer

Angelman syndrome is associated with the same region on chromosome 15 as Prader-Willi syndrome. Both disorders involve alterations or deletions in the 15q11-q13 region, but they differ based on whether the mutation is inherited from the mother (Angelman syndrome) or the father (Prader-Willi syndrome).

Question 8

Which term is used to describe a disorder that occurs only in individuals of a particular sex?&#10;A) Sex-influenced&#10;B) Y-linked&#10;C) X-linked&#10;D) Sex-limited&#10;E) Sex-determined

Accepted Answer

A disorder that occurs only in individuals of a particular sex is called sex-limited. This is because the expression of the trait is limited to one sex due to anatomical or hormonal differences. For example, breast cancer only affects females, while prostate cancer only affects males.

Answer choices A, B, C, and E are incorrect because they do not specifically refer to disorders that are limited to one sex. Sex-influenced traits may be expressed differently in males and females, but they are not limited to one sex. Y-linked traits are only expressed in males, but not all disorders that are limited to one sex are Y-linked. X-linked traits are inherited through the X chromosome, but they can be expressed in both males and females. Sex-determined refers to the process of determining an individual's sex during development, not to a specific type of disorder.

Question 9

Which of the following traits may exhibit holandric inheritance?&#10;A) Baldness&#10;B) Defects in spermatogenesis&#10;C) Webbed toes&#10;D) Red-green color blindness&#10;E) All of the above

Accepted Answer

Holandric inheritance refers to traits that are inherited through genes located on the Y chromosome. Since only males have the Y chromosome, these traits are exclusively passed from father to son. Defects in spermatogenesis can be linked to genes on the Y chromosome, making it a trait that may exhibit holandric inheritance.

Question 10

Traits that are observed in individuals who are heterozygous for mutations at two different loci are called&#8230;&#10;A) Digenic traits&#10;B) Biallelic traits&#10;C) Compound heterozygotes&#10;D) Compound traits&#10;E) Epistatic traits

Accepted Answer

Digenic traits are observed in individuals who are heterozygous for mutations at two different loci. Biallelic traits refer to traits controlled by two alleles at a single locus. Compound heterozygotes carry two different mutations in the same gene. Compound traits and epistatic traits do not specifically refer to traits observed in heterozygous individuals with mutations at multiple loci.

Question 11

Which of the following terms is used to describe the fact that mutations in a single gene can have more than one phenotypic effect?&#10;A) Pleiotropy&#10;B) Variable expressivity&#10;C) Variable penetrance&#10;D) Heteroplasmy&#10;E) Mosaicism

Accepted Answer

The answer of Which of the following terms is used...

Deck 7: Patterns of Inheritance