Question 1

Which one of the following pairings of an aneuploidy and the syndrome it causes is incorrectly matched?

Accepted Answer

D

Question 2

What percentage of parents decide to terminate a Down Syndrome pregnancy?

Accepted Answer

Studies have shown that a significant majority, around 90 percent, of parents choose to terminate a pregnancy when prenatal testing indicates Down Syndrome.

Question 3

A chromosome whose centromere is close to the end of the chromosome is called _______.

Accepted Answer

An acrocentric chromosome has its centromere located close to one end of the chromosome, causing one arm of the chromosome to be much shorter than the other.

Question 4

How does polyploidy differ from aneuploidy?

Accepted Answer

Polyploidy involves changes in entire chromosome sets, resulting in more than two sets of chromosomes, while aneuploidy involves a deviation from the typical diploid chromosome number, resulting in an extra or missing chromosome(s) within the set.

Question 5

When making a karyotype, what is the effect of placing lymphocytes in a low-salt solution?

Accepted Answer

Placing lymphocytes in a low-salt solution causes the cells to swell due to osmotic pressure, which helps spread the chromosomes apart for better visualization during karyotyping.

Question 6

The placement of chromosomes into one of the seven groups in a karyotype is based on the chromosome's

Accepted Answer

The answer of The placement of chromosomes into one of...

Question 7

The risk for Down syndrome increases in situations where the

Accepted Answer

The risk for Down syndrome increases as the mother's age increases, particularly after the age of 35. The age of the father is not as significant a factor in the risk for Down syndrome. Therefore, choice C, where the mother is 35-45 years old, is the best choice.

Question 8

If nondisjunction takes place in one of the cells of the second meiotic division, the four products of meiosis will include

Accepted Answer

In the second meiotic division, nondisjunction results in two normal gametes and two abnormal gametes, as one pair of sister chromatids fails to separate.

Question 9

The region at the end of a chromosome is termed the _______.

Accepted Answer

The region at the end of a chromosome is called a telomere. Options A, C, D, and E refer to other parts of the chromosome- centromere is the middle part, satellite refers to the darkly stained region near the centromere, and P and Q arms refer to the shorter and longer arms of a chromosome, respectively.

Question 10

The letters G, Q, R, and C are used to describe bands that appear on chromosomes. The letters refer to

Accepted Answer

The letters used to describe bands on chromosomes refer to the staining procedure that was used to reveal them. G-banding indicates the use of Giemsa staining, Q-banding indicates quinacrine staining, R-banding indicates relative staining, and C-banding indicates centromeric staining. These stains produce different patterns on the chromosomes, allowing them to be distinguished and studied under a microscope. The letters do not refer to the position, size, gene content, or relative importance of the bands.

Question 11

Characterize the frequency of changes in chromosome number in humans.

Accepted Answer

Close to half of all conceptions in humans are aneuploid, which means there is a change in chromosome number. These changes are a major cause of reproductive failure and are much more frequent in humans compared to closely related animals. Thus, all the given statements are correct and the best choice is D.

Question 12

Studies on aneuploidies of the sex chromosomes reveal that

Accepted Answer

The Y chromosome is not necessary for survival because individuals with Turner syndrome (XO) can survive without a Y chromosome.

Question 13

Most triploid zygotes arise from

Accepted Answer

Most triploid zygotes arise from the fertilization of a normal haploid egg by two sperm, a process known as dispermy.

Question 14

Chromosome painting is a relatively new technique in karyotype analysis. Which one of the following statements about chromosome painting is false?

Accepted Answer

In a normal karyotype, each chromosome may have regions that appear as bands of different colors, but chromosome painting specifically involves the use of fluorescent dyes to label specific DNA sequences, not banding patterns.

Question 15

The two most common types of polyploidy in humans are

Accepted Answer

Triploidy and tetraploidy are the two most common types of polyploidy in humans, where there are three or four sets of chromosomes, respectively.

Question 16

Amniocentesis and chorionic villus sampling are two methods of prenatal diagnosis. One important difference between these techniques is that

Accepted Answer

Chorionic villus sampling can be performed earlier in pregnancy, typically around 10-13 weeks, while amniocentesis is usually done at around 15-20 weeks. However, it should be noted that the specific timing and availability of these procedures may vary depending on the individual case and healthcare provider.

Question 17

Which of the following is not information derived from karyotypes?

Accepted Answer

Karyotypes provide information about the number, size, and shape of chromosomes, as well as any structural abnormalities present. However, they do not provide information about the pattern of inheritance of specific traits, which is determined by the genes located on the chromosomes.

Question 18

A translocation involving chromosome 21 can result in

Accepted Answer

Translocation involving chromosome 21 can result in the transfer of the genetic material from chromosome 21 to another chromosome. If the translocated chromosome (with a piece of 21) is then the one that goes into the gamete, it can result in Down syndrome in the offspring. This is independent of maternal or paternal age as it is a genetic mutation.

Question 19

The region that divides a chromosome into two arms is the ______.

Accepted Answer

The centromere is a specialized region on a chromosome that divides the chromosome into two arms, and it is the site where the kinetochore forms to attach to spindle fibers during cell division. The other options listed are not involved in dividing a chromosome into two arms.

Question 20

Fragile sites are chromosome locations that

Accepted Answer

Fragile sites are inherited in a codominant fashion, meaning both alleles contribute to the phenotype. They are specific areas on chromosomes that are prone to breaking under certain conditions.

Quiz 6: Cytogenetics: Karyotypes and Chromosome Aberrations