Question 1

Which chromosome is trisomic in Patau syndrome?

Accepted Answer

Patau syndrome is caused by a trisomy (presence of an extra copy) of chromosome 13.

Question 2

What would be the expected consequence to two daughter cells after mitosis if the ability to produce mitochondria was lost?

Accepted Answer

Mitochondria are responsible for producing ATP, the main source of energy for cells. If the ability to produce mitochondria was lost, the rate and amount of ATP production would be limited, which would ultimately affect cellular metabolism and function. This could lead to a range of negative consequences for the daughter cells, including impaired growth and survival. Therefore, choice C is the best option.

Question 3

What is the risk for a woman who had a retinoblastoma in early childhood as a result of a partial deletion on one number 13 chromosome to have a child who also develops the disorder?

Accepted Answer

Retinoblastoma is caused by a mutation or deletion in both copies of the RB1 gene. The patient in this scenario has a partial deletion on only one of their number 13 chromosomes, meaning they have one functioning copy of the RB1 gene.

When this patient has children, there is a 50% chance that they will pass on their affected chromosome 13 with the partial deletion, which would increase the risk of retinoblastoma in their child. However, there is also a 50% chance that they will pass on their normal chromosome 13, which would not increase the risk of retinoblastoma in their child.

Question 4

For a person who has any type of chromosomal abnormality,what factor(s)has/have the greatest impact on both physical and cognitive potential?

Accepted Answer

Although prenatal testing and diagnosis, the number of chromosomes involved with the abnormality, and the number of affected family members can provide valuable information, personal family environment and social interaction have the greatest impact on both physical and cognitive potential. A supportive and enriching environment can enhance an individual's abilities and opportunities, while a negative or neglectful environment can limit them.

Question 5

Which health screening activity is most important for girls and women with Turner syndrome?

Accepted Answer

The incidence of osteoarthritis, lung problems, and breast cancer is not increased in this population. Other health problems are common and can be significant for the person who has Turner syndrome, especially long-term hypertension and hyperlipidemia, which may be present even in early childhood.

Question 6

Which single physical feature is most often associated with a 47,XXX karyotype?

Accepted Answer

A karyotype of 47,XXX produces a physically normal phenotype, and the individual is fertile. The most outstanding and consistent feature is that these women are taller than average and are taller than most family members. Breast development is not affected by the extra X chromosome, and neither is hair loss.

Question 7

Which clinical feature is a common finding for infants with trisomy 21,trisomy 18,and trisomy 13?

Accepted Answer

A single palmar crease, also known as a simian crease, is a common finding in infants with all three chromosomal abnormalities: trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome). Other clinical features may differ between the three conditions.

Question 8

Which type of problems result from mutations in mitochondrial DNA (mtDNA)?

Accepted Answer

Mutations in mitochondrial DNA (mtDNA) often result in reduced cellular energy production, as the mitochondria play a crucial role in producing ATP through oxidative phosphorylation. Other types of mutations such as balanced translocations, excessive "crossing over", and single nucleotide polymorphisms are not typically associated with mtDNA mutations.

Question 9

What is the most common chromosomal abnormality conceived?

Accepted Answer

The answer of What is the most common chromosomal abnormality...

Question 10

What is the risk for a man with a 47,XYY karyotype to produce a child with a 47,XYY karyotype?

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 11

Which reproductive consequence is possible for a man who has a 13;15 Robertsonian translocation when his wife has a normal karyotype?

Accepted Answer

A Robertsonian translocation involves the fusion of two acrocentric chromosomes, resulting in a single larger chromosome. If the translocated chromosome is involved in gamete formation, it can lead to either a balanced or unbalanced gamete. In the case of a 13;15 Robertsonian translocation, the individual can produce gametes with either a balanced translocation (carrying both chromosome 13 and 15 material) or an unbalanced translocation (missing some genetic material from one or both chromosomes). If the individual produces an unbalanced gamete, it can result in a child with trisomy 13 or 15. If the individual produces a balanced gamete, it may still result in a child with an unbalanced karyotype if they inherit the translocated chromosome. As the wife has a normal karyotype, there are no increased risks for chromosomal abnormalities in her gametes.

Question 12

Why is Down syndrome the most common trisomy disorder seen among live born infants?

Accepted Answer

Trisomy as a result of nondisjunction can occur with any chromosome. Chromosome 21 contains few gene alleles. Trisomy of chromosomes containing more alleles is not compatible with life and is embryo lethal. Thus, the pregnancy does not progress beyond the first trimester.

Question 13

Which feature of a 15q deletion is present in both Angelman syndrome and Prader-Willi syndrome?

Accepted Answer

Skin, hair, and eye color that are lighter than those of other family members are features of both Angelman syndrome and Prader-Willi syndrome. Continuous smiling, jerky gait, and seizure activity occur with Angelman syndrome but not Prader-Willi syndrome. Excessive appetite and weight gain are associated with Prader-Willi syndrome but not Angelman syndrome.

Question 14

What is the risk for a man who has Down syndrome to produce a child with Down syndrome with a woman who has a normal karyotype?

Accepted Answer

Men with Down syndrome are typically infertile, and the risk of them fathering a child with Down syndrome is extremely low, approaching 0%.

Question 15

Which clinical feature in a newborn baby girl suggests the possibility of Turner syndrome?

Accepted Answer

Presence of a webbed neck is a key clinical feature of Turner syndrome, which is a genetic disorder that affects females and is characterized by the absence of part or all of one X chromosome. Absence of Babinski reflex, presence of epicanthal folds or absence of irises of both eyes are not associated with Turner syndrome.

Question 16

Which statement regarding partial chromosomal deletions or duplications is true?

Accepted Answer

Partial chromosomal deletions or duplications lead to an imbalance in gene dosage, resulting in either a triple dose (duplication) or a single dose (deletion) of some gene alleles.

Question 17

A male 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 is consistent with these findings?

Accepted Answer

The karyotype 47,XXY is consistent with Klinefelter syndrome, a congenital condition in which males have an extra X chromosome. This can lead to tall stature, gynecomastia, and a low sperm count. The other answer choices are not consistent with these findings.

Question 18

How is a Robertsonian translocation different from a reciprocal translocation?

Accepted Answer

A Robertsonian translocation is a specific type of balanced translocation created by the fusion of the entire long arms (q arms) of two acrocentric chromosomes with loss of the short arms (p arms). (The short arms of acrocentric chromosomes contain no gene alleles.) Reciprocal translocations are a specific type of translocation in which segments of two nonhomologous chromosomes break and are equally exchanged. The initial exchanges of material for reciprocal translocations and fusion of chromosomes for Robertsonian translocations are both balanced.

Question 19

Why does an embryo with a balanced translocation have the same chance for normal development that an embryo with a normal karyotype has?

Accepted Answer

The most important part of the beginning process in which a zygote is formed that has half its chromosomal material from its father and half from its mother is that the zygote inherits exactly the right amount of genetic material. The actual location of the genetic material is less important for normal growth, development, and function. With a balanced translocation, the right number of alleles is present (no more and no less) in both somatic and germline cells, but they are not all located in their customary places. Because this translocation is balanced, there is no specific risk either for abnormal development or miscarriage of the fetus who is a balanced translocation carrier. Neither phenotype nor physiologic function is affected. DNA repair mechanisms correct only individual base placement, not translocations.

Question 20

Which cancer type has an increased incidence among children with WAGR syndrome?

Accepted Answer

Nephroblastoma, also known as Wilms tumor, is a type of kidney cancer that occurs more frequently in children with WAGR syndrome.

Quiz 5: Chromosomal and Mitochondrial Inheritance and Disorders