Question 1

Which clinical feature in a newborn baby girl suggests the possibility of Turner syndrome?&#10;A)Absence of Babinski reflex&#10;B)Presence of a webbed neck&#10;C)Presence of epicanthal folds&#10;D)Absence of irises of both eyes

Accepted Answer

Girls with Turner syndrome are often identified at birth because of the presence of "classic" phenotypic features. These include a smaller-than-expected size at full-term pregnancy, neck webbing, pedal edema, and cardiac abnormalities. These children have a normal early neurologic response, including Babinski reflex. Although epicanthal folds often occur in Turner syndrome, they are not unique to this syndrome. Aniridia is associated with WGAR syndrome and is not found in Turner syndrome.

Question 2

At what specific location on an X chromosome is a break most likely to occur in fragile X syndrome?&#10;A)The centromere&#10;B)End of the p arm&#10;C)End of the q arm&#10;D)Within the nucleosome

Accepted Answer

The term fragile X comes from the fact that when chromosomal analysis is performed under certain laboratory conditions, the X chromosome often has a small break or gap at the end of the long arm.

Question 3

Which process can cause a person with an XY genotype to have a female phenotype?&#10;A)Pregnancy resulting from artificial insemination in which the semen donor is homosexual&#10;B)Mating of a man who has Klinefelter syndrome with a woman who has Turner syndrome&#10;C)An epigenetic disorder in which the X chromosome inactivates the Y chromosome&#10;D)Failure of gene expression resulting in a complete absence of androgen receptors

Accepted Answer

The situation resulting in a person with an XY genotype having a naturally occurring female phenotype is complete androgen insensitivity or androgen insensitivity syndrome (AIS). In this condition, all tissues, including the masculine tissues (mesonephric ductal tissues), are missing androgen receptors. The presence of the Y chromosome starts the organization of the bipotential gonad into a testis with the secretion of testosterone; however, the testosterone has no developmental influence on the mesonephric ductal tissues because they lack the receptors for binding and allowing the testosterone to change the gene activity of these cells. Thus, the mesonephric ducts regress, and the paramesonephric ducts undergo partial growth. At birth, the child has very clear female external genitalia, and this phenotype continues throughout life. The girl does go through her adolescent growth spurt and starts to develop hip curves and breasts but does not begin menstruation. She cannot become pregnant but is female in every other sense. The position of the bipotential gonad does not influence its function. Klinefelter men and Turner women are infertile. The X chromosome does not inactivate the Y chromosome.

Question 4

Which of the following mechanisms in fragile X syndrome (FXS) leads to expression of the disorder?&#10;A)Trinucleotide repeat sequences interspersed with the exons of the FMR1 gene, resulting in the production of an abnormal protein&#10;B)Trinucleotide repeat sequences causing methylation of the FMR1 gene, thus silencing its expression&#10;C)Increased production of microRNA molecules that interfere with the transcription of the FMR1 gene&#10;D)Increased production of microRNA molecules that interfere with the translation of the FMR1 gene

Accepted Answer

In FXS, the FMR1 gene-coding regions are normal, but the gene's expression is silenced by large numbers of the trinucleotide sequence of CGG being repeated within the noncoding regions of the gene.

Question 5

Which trait or characteristic in a 10-year-old-girl would lead her pediatrician to consider the possibility of androgen insensitivity syndrome?&#10;A)Her ears are large and stick out.&#10;B)She is color-blind, and her father is not.&#10;C)She is an inch taller than her siblings were at age 10.&#10;D)Her nipples and breasts have not started to change and develop.

Accepted Answer

The gene for color vision is on the X chromosome and is recessive. Thus, color-blindness is an X-linked-recessive disorder resulting from a mutation in the gene. If a male inherits this gene from his mother, he will express color-blindness. If a girl inherits this gene from her mother, she will only express color-blindness if her father is color-blind.

Question 6

What is the function of the FMR1 gene?&#10;A)Promoting brain development and maintaining neuronal synapses&#10;B)Ensuring the expression of all other genes present on the X chromosome&#10;C)Preventing amyloid plaque deposits and formation of neuronal tangles in the brain&#10;D)Maintaining the structural integrity of the histone proteins surrounding the X chromosome

Accepted Answer

The FMR1 gene, which is located on the X chromosome, codes for a protein that is critical in brain development and maintenance of neural synapses. If this protein is not produced in sufficient amounts or is abnormal, reduced cognition occurs, especially in males. FMX1 stands for fragile X mental retardation 1. Mutations are not responsible for the amyloid plaques and neuronal tangles that develop in Alzheimer's disease.

Question 7

Which of the following definitions accurately represents the concept of expansion?&#10;A)The phenotype of a genetic condition is expressed with greater severity and at earlier ages with succeeding generations.&#10;B)The number of trinucleotide repeat sequences within the noncoding region of a specific gene allele is increased.&#10;C)The number of copies of a specific gene allele is amplified on one chromosome of a homologous pair.&#10;D)A specific gene allele has at least two copies of every exon within the gene.

Accepted Answer

Expansion is an increase, usually of trinucleotide repeat sequences within a gene. The definition of response A is that of anticipation. The definition of response C is amplification. Response D is just a mutation that would result in either an inappropriate protein or no protein produced.

Question 8

What is the risk for a man with a 47,XYY karyotype to produce a child with a 47,XYY karyotype?&#10;A)100%&#10;B)50%&#10;C)25%&#10;D)0%

Accepted Answer

Men with a 47,XYY karyotype are fertile. Because the extra Y chromosome is likely to be present in approximately 50% of mature spermatozoa, the risk for a man with this karyotype to produce a child who is also 47,XYY is also 50%.

Question 9

On which chromosome is the androgen receptor (AR) gene located?&#10;A)1&#10;B)21&#10;C)X&#10;D)Y

Accepted Answer

Even though men have more androgen receptors than do women, the AR gene is located on the X chromosome, not the Y. Women do produce small amounts of androgens in the adrenal gland, which need to bind to the AR receptors in order to produce their effects.

Question 10

Which condition or health problem is more common in women who have an FMR1 mutation?&#10;A)Emotional instability with inappropriate expression of anger&#10;B)Patchy areas of decreased skin pigmentation&#10;C)Progressive skeletal muscle weakness&#10;D)Menopause before age 40 years

Accepted Answer

Women with FMR1 mutations or trinucleotide repeat sequences that categorizes them as premutation carriers can develop fragile X-associated primary ovarian insufficiency syndrome (FXPOI), which is an early onset of ovarian failure causing the onset of menopause in women who are premutation carriers at ages under 40 years.

Question 11

Which feature is common among people who have Klinefelter syndrome (47,XXY) or a karyotype with 47,XXX but not among people who have Down syndrome or Edward syndrome?&#10;A)Severely reduced cognition&#10;B)Cleft palate&#10;C)Tall stature&#10;D)Infertility

Accepted Answer

The answer of Which feature is common among people who...

Question 12

Amale patient is tall and has some gynecomastia along with a low sperm count. During infertility testing, he was found to have a 47,XXY karyotype. Which disorder isconsistent with these findings?&#10;A)Normal male&#10;B)Turner syndrome&#10;C)Klinefelter syndrome&#10;D)Testicular feminization syndrome

Accepted Answer

The answer of Amale patient is tall and has some...

Question 13

What factor most strongly influences the development of the paramesonephric tissue into female sex organs?&#10;A)Proper positioning of the bipotential gonad&#10;B)The presence of estrogen during puberty&#10;C)The presence of two X chromosomes&#10;D)The absence of a Y chromosome

Accepted Answer

The answer of What factor most strongly influences the development...

Question 14

Which health screening activity is most important for girls and women with Turner syndrome?&#10;A)Mammography&#10;B)Test for osteoarthritis&#10;C)Blood pressure screening&#10;D)Pulmonary function testing

Accepted Answer

The answer of Which health screening activity is most important...

Question 15

A man and his sister are both affected with a mitochondrial disorder. Because the sister has two children who also have the disorder, the man is concerned about thepossibility of also having children with the disorder. What is the estimated risk for each pregnancy of this man producing a child with the same mitochondrial disorder that he has if his wife does not have a mitochondrial disorder?

A)100%
B)50%
C)25%
D)0%

Accepted Answer

The answer of A man and his sister are both...

Question 16

What is the most likely mechanism for a 45,X karyotype?&#10;A)Anticipation&#10;B)Nondisjunction&#10;C)Expansion&#10;D)Heteroplasmy

Accepted Answer

The answer of What is the most likely mechanism for...

Question 17

Which single physical feature is most often associated with a 47,XXX karyotype?&#10;A)Infertility&#10;B)Large breasts&#10;C)Female-pattern baldness&#10;D)Height greater than siblings

Accepted Answer

The answer of Which single physical feature is most often...

Question 18

Why is the incidence of an extra Y chromosome in the general population unknown?&#10;A)The phenotype is that of a normal male.&#10;B)Most conceptions with 47,XYY are spontaneously aborted.&#10;C)The life expectancy for males with 47,XYY is often short.&#10;D)The majority of males with this sex chromosome abnormality are institutionalized.

Accepted Answer

The answer of Why is the incidence of an extra...

Question 19

What would be the expected consequence to two daughter cells after mitosis if the ability to produce mitochondria was lost?&#10;A)Cell commitment and differentiation would fail to occur.&#10;B)The process of protein synthesis could not be controlled.&#10;C)The rate and amount of ATP production would be limited.&#10;D)Future cell division would result in an uneven number of cells.

Accepted Answer

The answer of What would be the expected consequence to...

Question 20

Which type of problem results from mutations in mitochondrial DNA (mtDNA)?&#10;A)Reduced cellular energy&#10;B)Balanced translocations&#10;C)Excessive &#34;crossing over&#34;&#10;D)Single-nucleotide polymorphisms

Accepted Answer

The answer of Which type of problem results from mutations...

Deck 7: Sex Chromosome and Mitochondrial Inheritance and Disorders