Question 1

What is a syndrome?
A) a characteristic facial appearance
B) a trait that leads to cancer at some stage in life
C) a group of traits typically found in conjunction with a particular chromosomal aberration or gene mutation
D) a specific characteristic that appears in conjunction with one specific aneuploidy

Accepted Answer

A syndrome is a group of traits that are consistently found together and are often associated with a particular chromosomal aberration or gene mutation. While some syndromes may have a characteristic facial appearance or lead to an increased risk of cancer, these are not defining characteristics of a syndrome. A specific characteristic appearing in conjunction with one specific aneuploidy would not qualify as a syndrome unless it included a consistent group of traits.

Question 2

A phenotypically normal prospective couple seeks genetic counseling because the man knows that he has a translocation of a portion of his chromosome 4, which has been exchanged with a portion of his chromosome 12. Although his translocation is balanced, he and his wife want to know the probability that his sperm will be abnormal. What is your prognosis regarding his sperm?
A) One-quarter will carry the two normal chromosomes, 4 and 12, one-quarter will have only the two translocation chromosomes and no normal chromosomes 4 and 12, and half will have one normal and one translocated chromosome.
B) All will carry the same translocation as the father.
C) None will carry the translocation.
D) Half will be normal, and the rest will have the father's translocation.

Accepted Answer

The father's translocation involves a portion of chromosome 4 and a portion of chromosome 12. As a result, there are three possibilities for the offspring's chromosomes: normal chromosomes 4 and 12 (from the mother) and normal chromosomes 4 and 12 (from the father); translocated chromosomes 4 and 12 (from the father); or one normal chromosome 4 (from the mother or the father) and one translocated chromosome 4/12 (from the father). The probability of each of these three possibilities is equal, which means that one-quarter of the offspring will carry the two normal chromosomes, one-quarter will have only the two translocation chromosomes and no normal chromosomes 4 and 12, and half will have one normal and one translocated chromosome. Therefore, the prognosis regarding the father's sperm is that half will be normal, and the rest will have the father's translocation.

Question 3

Which of the following statements correctly describes what happens to a chromosome after a nonreciprocal translocation occurs?
A) A deletion of part of the chromosome occurs.
B) A duplication of part of the chromosome occurs.
C) Nondisjunction of pairs of homologous occurs.
D) A chromosome transfers a fragment but receives none in return.

Accepted Answer

Nonreciprocal translocation involves the transfer of a fragment from one chromosome to another, but one of the chromosomes involved does not receive any fragment in return. This results in a chromosome with a deleted portion and another chromosome with an extra piece.

Question 4

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this type of chromosomal alteration called?
A) deletion
B) inversion
C) translocation
D) duplication

Accepted Answer

This type of chromosomal alteration is called translocation. Deletion refers to the loss of a chromosomal segment, inversion refers to a reversal in orientation of a chromosomal segment, and duplication refers to the presence of an extra copy of a chromosomal segment.

Question 5

Mitochondrial DNA is primarily involved in coding for proteins needed for protein complexes of the electron transport chain and ATP synthase. Therefore, mutations in mitochondrial genes would most affect which of the following processes?
A) DNA synthesis in cells of the immune system
B) the movement of oxygen into erythrocytes
C) generation of ATP in muscle cells
D) the storage of urine in the urinary bladder

Accepted Answer

Mitochondrial DNA is primarily involved in coding for proteins needed for the electron transport chain and ATP synthase, which are involved in the generation of ATP in muscle cells. Mutations in mitochondrial genes could therefore significantly affect the ability of muscle cells to produce ATP, which could impact muscle function and overall energy metabolism. DNA synthesis in cells of the immune system, the movement of oxygen into erythrocytes, and the storage of urine in the urinary bladder are not directly related to mitochondrial DNA and would not be significantly impacted by mutations in these genes.

Question 6

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?
A) The woman inherited this tendency from her parents.
B) The mother had a chromosomal duplication.
C) One member of the couple underwent nondisjunction in somatic cell production.
D) One of the gametes in the mother most likely underwent nondisjunction during meiosis.

Accepted Answer

The most common cause of Down syndrome is nondisjunction during meiosis in one of the gametes of the mother, resulting in an extra copy of chromosome 21. The mother's age, 39, also increases the likelihood of such a mistake occurring. Options A and B are not likely causes of Down syndrome, and option C is referring to nondisjunction in body cells, which would not result in a child with Down syndrome.

Question 7

Inheritance patterns cannot always be explained by Mendel's models of inheritance. If a pair of homologous chromosomes fails to separate during meiosis I, select the choice that shows the chromosome number of the four resulting gametes with respect to the normal haploid number (n)?
A) n + 1; n + 1; n - 1; n - 1
B) n + 1; n - 1; n; n
C) n + 1; n - 1; n - 1; n - 1
D) n + 1; n + 1; n; n

Accepted Answer

The answer of Inheritance patterns cannot always be explained by...

Question 8

A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following statements describes her expected phenotype?
A) a female with masculine characteristics such as facial hair
B) an apparent male who is sterile
C) healthy female of slightly above-average height
D) a sterile female

Accepted Answer

This individual has a case of Triple X syndrome, also known as 47,XXX. This syndrome occurs in approximately 1 in 1,000 female births. Females with Triple X syndrome generally have a typical female phenotype, with the only noticeable difference being slightly above-average height. They do not typically have masculine characteristics or sterility.

Question 9

Which of the following correctly describes a Philadelphia chromosome?
A) a human chromosome 22 that has had a specific translocation
B) a human chromosome 9 that is found only in one type of cancer
C) an animal chromosome found primarily in the mid-Atlantic area of the United States
D) a chromosome found only in mitochondria

Accepted Answer

The Philadelphia chromosome is a specific translocation of human chromosome 22, where a segment of the chromosome moves to attach to chromosome 9. It is commonly found in chronic myeloid leukemia (CML) and some other types of blood cancers.

Question 10

Use the following figure to answer the question.

The pedigree in the figure shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely ________.
A) mitochondrial
B) sex-linked dominant
C) sex-linked recessive
D) autosomal dominant

Accepted Answer

The answer of Use the following figure to answer the...

Question 11

Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?
A) 47, trisomy 21
B) 47, XXY
C) 47, XXX
D) 45, X

Accepted Answer

Trisomy 21, also known as Down syndrome, is generally considered the aneuploidy that has the most severe impact on the health of the individual. It is associated with intellectual disability, physical abnormalities, and an increased risk for certain health conditions such as heart defects, hearing loss, and Alzheimer's disease.

Question 12

Genomic imprinting is generally due to the addition of methyl (-CH₃)groups to C nucleotides and chemical histone changes to silence a given gene. If this depends on the sex of the parent who transmits the gene, which of the following statements must be true?
A) Genes required for early development stages must not be imprinted.
B) Methylation of this kind must occur more in males than in females.
C) Methylation must be reversible in ovarian and testicular cells.
D) The imprints are transmitted only to gamete-producing cells.

Accepted Answer

The answer of Genomic imprinting is generally due to the...

Question 13

German scientist Carl Correns found that the inheritance of variegated color on the leaves of certain plants was determined only by the maternal parent. What phenomenon explains this pattern of inheritance?
A) ribosome structure
B) inheritance of plastid genes
C) genomic imprinting
D) sex linkage

Accepted Answer

The inheritance of variegated color on the leaves of certain plants being determined only by the maternal parent is due to the inheritance of plastid genes. Plastid genes are only inherited from the maternal parent, as the egg cell contributes the cytoplasm and organelles to the zygote during fertilization.

Question 14

Which of the following statements is generally true of aneuploidies in newborns?
A) A monosomy is more frequent than a trisomy.
B) Monosomy X is the only viable monosomy known to occur in humans.
C) Human aneuploidy usually conveys an adaptive advantage in humans.
D) An aneuploidy resulting in the deletion of a chromosome segment is less serious than a duplication.

Accepted Answer

Monosomy X, also known as Turner syndrome, is the only viable monosomy known to occur in humans. All other monosomies usually result in spontaneous abortion or stillbirth. Trisomies are more common than monosomies and can result in various genetic disorders such as Down syndrome, Edwards syndrome and Patau syndrome. Human aneuploidy usually conveys a disadvantage rather than an advantage, and an aneuploidy resulting in the deletion or duplication of a chromosome segment can have varying effects depending on the extent and location of the alteration.

Question 15

Which of the following is an example of monosomy in humans?
A) Turner syndrome
B) Klinefelter syndrome
C) Down syndrome
D) trisomy X

Accepted Answer

Monosomy refers to the presence of only one copy of a particular chromosome instead of the normal two. Turner syndrome is caused by the absence of one X chromosome in females, resulting in monosomy of the X chromosome.

Question 16

A certain kind of snail can have a right-handed direction of shell coiling (DD or Dd)or left-handed coiling (dd). However, if direction of coiling is due to a protein deposited by the mother in the egg cytoplasm, then a Dd egg-producing snail and a dd sperm-producing snail will have offspring of which genotype(s)and phenotype(s)?
A) 1/2 Dd:1/2 dd; all right-coiling
B) all Dd; all right-coiling
C) 1/2 Dd: 1/2 dd; half right-coiling and half left-coiling
D) all Dd; half right-coiling and half left-coiling

Accepted Answer

The answer of A certain kind of snail can have...

Question 17

Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following events might then occur to make the cancer worse?
A) an increase in nondisjunction
B) expression of inappropriate gene products
C) a decrease in mitotic frequency
D) failure of the cancer cells to multiply

Accepted Answer

Translocations can result in genes being under the control of inappropriate regulatory sequences, leading to the expression of abnormal or overactive gene products, contributing to the development of cancer. Option A, an increase in nondisjunction, is not directly related to the effects of translocations on cancer development. Option C, a decrease in mitotic frequency, would actually slow down the growth and spread of cancer cells, potentially making it easier to treat. Option D, failure of cancer cells to multiply, would be ideal for cancer treatment, but it is not a common outcome of abnormal chromosomes or translocations.

Question 18

During meiosis, a defect occurs in a cell that results in the failure of spindle microtubules binding at the kinetochores. Which of the following statements describes the most likely result of such a defect?
A) New microtubules with more effective binding capabilities to kinetochores will be synthesized to compensate for the defect.
B) Excessive cell divisions will occur resulting in cancerous tumors and an increase in the chromosome numbers known as polyploidy.
C) The defect will be bypassed in order to ensure normal chromosome distribution in the new cells.
D) The resulting cells will not receive the correct number of chromosomes in the gametes, a condition known as aneuploidy.

Accepted Answer

Without proper attachment of spindle microtubules to kinetochores, the chromosomes will not be properly separated during meiosis, leading to aneuploidy in the resulting cells. Aneuploidy is a condition where cells have an abnormal number of chromosomes, which can lead to developmental disorders or disease. Option A is incorrect because microtubules cannot be synthesized during meiosis once the process has started. Option B is incorrect because polyploidy results from errors in cell division during mitosis, not meiosis. Option C is incorrect because the defect cannot be bypassed - proper spindle microtubule attachment is essential for normal chromosome segregation.

Quiz 15: The Chromosomal Basis of Inheritance

What is a syndrome?

Which of the following statements correctly describes what happens to a chromosome after a nonreciprocal translocation occurs?

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this type of chromosomal alteration called?

Mitochondrial DNA is primarily involved in coding for proteins needed for protein complexes of the electron transport chain and ATP synthase. Therefore, mutations in mitochondrial genes would most affect which of the following processes?

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?

Inheritance patterns cannot always be explained by Mendel's models of inheritance. If a pair of homologous chromosomes fails to separate during meiosis I, select the choice that shows the chromosome number of the four resulting gametes with respect to the normal haploid number (n) ?

A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following statements describes her expected phenotype?

Which of the following correctly describes a Philadelphia chromosome?

Use the following figure to answer the question. The pedigree in the figure shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely ________.

Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?

Genomic imprinting is generally due to the addition of methyl (-CH₃) groups to C nucleotides and chemical histone changes to silence a given gene. If this depends on the sex of the parent who transmits the gene, which of the following statements must be true?

German scientist Carl Correns found that the inheritance of variegated color on the leaves of certain plants was determined only by the maternal parent. What phenomenon explains this pattern of inheritance?

Which of the following statements is generally true of aneuploidies in newborns?

Which of the following is an example of monosomy in humans?

Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following events might then occur to make the cancer worse?

During meiosis, a defect occurs in a cell that results in the failure of spindle microtubules binding at the kinetochores. Which of the following statements describes the most likely result of such a defect?