1.
Which of the following statements is NOT true about Karyotypes?
Correct Answer
B. Having missing or extra chromosomes does not indicate a disorder
Explanation
This statement is not true because having missing or extra chromosomes can indicate a disorder. For example, Down syndrome is caused by an extra copy of chromosome 21. Additionally, missing or extra chromosomes can lead to other genetic disorders and abnormalities.
2.
What could be the result of nondisjunction?
Correct Answer
D. All of the above
Explanation
Nondisjunction is the failure of chromosomes to separate properly during cell division. This can result in various genetic conditions. Trisomy conditions occur when there is an extra copy of a chromosome, such as Down syndrome (trisomy 21). Monosomy conditions occur when there is a missing copy of a chromosome, such as Turner syndrome (monosomy X). Nondisjunction can also lead to the presence of additional sex chromosomes, such as Klinefelter syndrome (XXY) or Turner syndrome (X0). Therefore, all of the options mentioned (trisomy conditions, monosomy conditions, additional sex chromosomes) can be the result of nondisjunction.
3.
It is likely that as many as __________ newborn infants inherit a chromosomal abnormality.
Correct Answer
A. 1 in 118
Explanation
Approximately 1 in 118 newborn infants are likely to inherit a chromosomal abnormality. This suggests that there is a relatively high prevalence of chromosomal abnormalities among newborns.
4.
What can occur if the chromosomes fail to separate correctly during the anaphase of meiosis?
Correct Answer
C. Extra chromosomes are found in the sex cell
Explanation
During the anaphase of meiosis, chromosomes are supposed to separate correctly and move to opposite poles of the cell. However, if they fail to separate correctly, it can result in extra chromosomes being found in the sex cell. This is known as nondisjunction, where chromosomes do not separate evenly, leading to an abnormal number of chromosomes in the resulting sex cell. This can have significant consequences, as it can lead to genetic disorders or abnormalities in offspring if the abnormal sex cell is involved in fertilization.
5.
If a child had a karyotype that had 23 + 23 + 23 chromosomes or 23 + 24, it would be:
Correct Answer
A. An irregular number of chromosomes
Explanation
If a child had a karyotype with 23 + 23 + 23 chromosomes or 23 + 24, it would be considered an irregular number of chromosomes. A normal karyotype for a human has 46 chromosomes, with 23 pairs. Any deviation from this number would be considered abnormal and indicate an irregular number of chromosomes.
6.
Down's syndrome occurs because of a(n)
Correct Answer
A. Additional 21st chromosome
Explanation
Down's syndrome occurs because of an additional 21st chromosome. Normally, a person has two copies of each chromosome, but individuals with Down's syndrome have three copies of chromosome 21. This extra genetic material disrupts the normal development and causes the characteristic physical and intellectual disabilities associated with the syndrome.
7.
The phase in mitosis where chromosomes move away and are pulled apart by spindles to opposite sides of the cell.
Correct Answer
D. AnapHase
Explanation
Anaphase is the correct answer because it is the phase in mitosis where the chromosomes move away from each other and are pulled apart by spindle fibers towards opposite poles of the cell. During anaphase, the sister chromatids separate and become individual chromosomes, which are then pulled towards the opposite ends of the cell. This movement ensures that each daughter cell receives the correct number of chromosomes during cell division.
8.
What would you call the failure of one or more pairs of sister chromatids to separate normally during meiosis?
Correct Answer
B. Nondisjunction
Explanation
Nondisjunction refers to the failure of sister chromatids to separate properly during meiosis. This can result in an abnormal distribution of chromosomes in the resulting gametes, leading to genetic disorders such as Down syndrome. Anaphase I, on the other hand, is a phase of meiosis where homologous chromosomes separate, not sister chromatids. Nondiploidy refers to an abnormal number of chromosomes, and karyotype is a visualization of an individual's chromosomes. Therefore, the correct answer is nondisjunction.
9.
A structural modification of a chromosome might be:
Correct Answer
C. A break in a chromatid arm and its separation from its chromosome
Explanation
A structural modification of a chromosome refers to any alteration in the normal structure of a chromosome. This can include a break in a chromatid arm and its separation from its chromosome, which is known as a chromosomal deletion. Miscarriage or spontaneous abortion is not a structural modification of a chromosome but rather a pregnancy loss. A karyotype, on the other hand, is a visual representation of the chromosomes in an individual's cells and can be used to detect structural abnormalities. Therefore, the correct answer is a break in a chromatid arm and its separation from its chromosome.
10.
Inherited chromosomal abnormalities usually result from:
Correct Answer
C. Defective sperm or ova
Explanation
Inherited chromosomal abnormalities usually result from defective sperm or ova. This means that the abnormalities are passed down from the parents to their offspring through the genetic material in the sperm or egg cells. These abnormalities can lead to various genetic disorders or conditions in the child, as the genetic information is not properly transmitted or may be altered.