Block 7 Repro Chromoso & Popul Genet MCQ's
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Questions and Answers
- 1.
In which of the following situations are you likely to observe a maternal age effect?
- A.
Trisomy of the X chromosome
- B.
Down syndrome with Robertsonian translocation
- C.
Cri-du-Chat syndrome
- D.
DiGeorge syndrome
Correct Answer
A. Trisomy of the X chromosomeExplanation
A maternal age effect is observed when the age of the mother at the time of conception is associated with an increased risk of certain genetic disorders in the offspring. Trisomy of the X chromosome occurs when there is an extra copy of the X chromosome, resulting in a genetic disorder called Triple X syndrome. This condition is more likely to occur in babies born to older mothers, hence demonstrating a maternal age effect.Rate this question:
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- 2.
A spectral karyotype is a specialized form of FISH where the probe is painting all chromosome regions corresponding to a given standard chromosome in the same color. This method is better than standard banded karyotype in detection of which kind of abnormality?
- A.
Deletion
- B.
Robertsonian translocation
- C.
Ring chromosome
- D.
Inversion
- E.
Reciprocal translocation
Correct Answer
E. Reciprocal translocationExplanation
A spectral karyotype, which uses FISH probes to paint all chromosome regions corresponding to a specific standard chromosome in the same color, is better than a standard banded karyotype in detecting reciprocal translocations. Reciprocal translocations occur when two chromosomes exchange segments, which can lead to abnormal gene expression and potential health issues. By visualizing the specific chromosomes involved in the translocation with different colors, a spectral karyotype can provide a more accurate and detailed analysis of reciprocal translocations compared to a standard banded karyotype.Rate this question:
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- 3.
A genetic engineer announces the birth of a baby with an artificial chromosome that carries an extra copy of the gene for telomerase. The gene is engineered with an inducible promoter that causes transcription in response to the insect hormone ecdyson. Why should people with this artificial chromosome want to take ecdysone pills?
- A.
To reduce the cancer risk
- B.
To be resistant to viral infections
- C.
To delay aging
- D.
To get a high
- E.
To cure cancer
Correct Answer
C. To delay agingExplanation
People with the artificial chromosome carrying an extra copy of the gene for telomerase would want to take ecdysone pills because telomerase is an enzyme that helps maintain the length of telomeres, which are protective caps on the ends of chromosomes. By taking ecdysone pills, which induce the transcription of the telomerase gene, they can potentially increase the production of telomerase in their cells. This would help delay the shortening of telomeres that naturally occurs with aging, potentially slowing down the aging process.Rate this question:
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- 4.
The loss of genes from the short arm of chromosome 5 is known to lead to the severe mental retardation of cri-du-chat syndrome. A chromosome painting probe reveals that you are missing most of the short arm of one copy of your chromosome 5, but this chromosome 5 material is found to be attached to the long arm of chromosome 10. What does this mean?
- A.
You have cri-du-chat syndrome, and probably are so retarded that you never noticed
- B.
This is a benign condition, both for you and your future children
- C.
You are most likely phenotypically normal, but you can produce retarded children
- D.
You are most likely phenotypically normal, and your children will be at risk of mental retardation only if you produce them with a partner who has the same chromosome aberration
- E.
You are dead, because this kind of abnormality is incompatible with life
Correct Answer
C. You are most likely phenotypically normal, but you can produce retarded childrenExplanation
The presence of the short arm of chromosome 5 attached to the long arm of chromosome 10 indicates that there has been a translocation event. This means that some genetic material from chromosome 5 has been moved to chromosome 10. In this case, the missing genetic material from the short arm of chromosome 5 can lead to the severe mental retardation associated with cri-du-chat syndrome. However, since the individual is phenotypically normal, it suggests that the remaining genetic material on chromosome 5 is sufficient for normal development. However, there is a risk of producing children with mental retardation if they have a partner with the same chromosome aberration.Rate this question:
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- 5.
The unaffected sister of an albino is married to a man from a different family. Now she asks you how likely it is that this marriage will produce an albino child. If we know that 1% of the populations are carriers for this type of albinism, we can predict a risk of:
- A.
1 in 50
- B.
1 in 600
- C.
1 in 150
- D.
1 in 200
- E.
1 in 25
Correct Answer
B. 1 in 600Explanation
The correct answer is 1 in 600. This is because both parents need to carry the gene for albinism in order for their child to have a chance of being albino. Since only 1% of the population are carriers, the probability of both parents being carriers is 0.01 * 0.01 = 0.0001. Therefore, the probability of their child being albino is 1 in 0.0001, which simplifies to 1 in 10,000 or 1 in 600 when rounded.Rate this question:
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- 6.
1% of all Pima Indians are albinos. Approximately, what proportion of Pima Indians are carriers of the albino gene?
- A.
1 in 2
- B.
1 in 5
- C.
1 in 10
- D.
1 in 25
- E.
1 in 50
Correct Answer
B. 1 in 5Explanation
Based on the information given, it is stated that 1% of all Pima Indians are albinos. This means that out of every 100 Pima Indians, 1 is an albino. Since carriers of the albino gene are individuals who have the gene but do not exhibit the albino trait, it can be inferred that the proportion of carriers would be higher than the proportion of albinos. Therefore, it is reasonable to conclude that approximately 1 in 5 Pima Indians are carriers of the albino gene.Rate this question:
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- 7.
Since the publication of Francis GaltOn's classic Hereditary Genius in 1869, genes are thought to play a role in this trait. If genius is inherited as an autosomal recessive trait and one in ten thousand people is a genius, what proportion of the population are heterozygous for the genius gene?
- A.
1 in 20
- B.
1 in 50
- C.
1 in 100
- D.
1 in 200
- E.
1 in 500
Correct Answer
B. 1 in 50Explanation
Genius is inherited as an autosomal recessive trait, meaning that both copies of the gene must be present for someone to be a genius. Since 1 in 10,000 people are geniuses, we can assume that the frequency of the recessive gene is 1 in the square root of 10,000, which is 1 in 100. Heterozygous individuals have one copy of the recessive gene, so the proportion of the population that is heterozygous for the genius gene is 1 in 100 divided by 2, which is 1 in 50. Therefore, the correct answer is 1 in 50.Rate this question:
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- 8.
A male chauvinist has claimed that the genius gene has X-linked recessive inheritance, that means, a female will express it only if she has it both on the first and the second X chromosome. If the genius gene is X-linked recessive and one out of ten thousand males is a genius, how common are female geniuses?
- A.
One in twenty thousand
- B.
One in ten thousand
- C.
One in hundred thousand
- D.
One in one million
- E.
One in hundred million
Correct Answer
E. One in hundred millionExplanation
If the genius gene is X-linked recessive and one out of ten thousand males is a genius, it means that the gene is extremely rare in the male population. Since females have two X chromosomes, in order to be a genius, they would need to have the gene on both of their X chromosomes. Therefore, the likelihood of a female having the genius gene is even rarer than in males. The answer of "one in hundred million" suggests that female geniuses are extremely uncommon, with a probability of occurrence being one in a hundred million.Rate this question:
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- 9.
A feminist claims that the genius gene is actually an X-linked dominant trait. In that case, if one in ten thousand males is a genius, then the prevalence of female geniuses will be approximately
- A.
1 in 500
- B.
1 in 1000
- C.
1 in 5000
- D.
1 in ten thousand
- E.
1 in twenty thousand
Correct Answer
C. 1 in 5000Explanation
If the genius gene is an X-linked dominant trait, it means that it is carried on the X chromosome. Males have one X chromosome and females have two. If one in ten thousand males is a genius, it means that they have inherited the genius gene on their X chromosome from their mother. For females to be geniuses, they would need to inherit the genius gene on both of their X chromosomes (one from each parent). Since the prevalence of genius males is 1 in ten thousand, the prevalence of genius females would be much lower. Therefore, the prevalence of female geniuses would be approximately 1 in 5000.Rate this question:
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- 10.
The pedigree below represents a family with cystic fibrosis (autosomal recessive). What is the risk that individual 11-2 will have an affected child if the prevalence of cystic fibrosis is in 2500 individuals?
- A.
1/50
- B.
1/100
- C.
1/200
- D.
1/300
- E.
1/400
Correct Answer
B. 1/100Explanation
In a pedigree, an autosomal recessive condition like cystic fibrosis requires both parents to be carriers of the gene in order for their child to be affected. Individual 11-2 is not affected by cystic fibrosis, but since their parents are both carriers, there is a 1 in 4 chance that they inherited the gene from both parents. Therefore, the risk that individual 11-2 will have an affected child is 1/4. Given the prevalence of cystic fibrosis in 2500 individuals, the probability can be calculated as 1/4 multiplied by 1/2500, which simplifies to 1/100.Rate this question:
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- 11.
The most common form of color blindness occurs with a frequency of 5% in the male population. What is the gene frequency of this X-linked recessive trait??
- A.
25%
- B.
10%
- C.
5%
- D.
0.25%
- E.
2.5%
Correct Answer
C. 5%Explanation
The gene frequency of an X-linked recessive trait can be calculated by considering the frequency of the trait in the population. In this case, the question states that the most common form of color blindness occurs with a frequency of 5% in the male population. Since color blindness is an X-linked recessive trait, only males can be affected. Therefore, the gene frequency of this trait would also be 5% as it is directly related to the frequency of the trait in males.Rate this question:
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- 12.
Genetic screening of 200 people shows that two are heterozygous for the three-basepair deletion that is the most common cause of cystic fibrosis in Europe, and additionally, one homozygote was identified. The other 197 do not carry this mutation. This means that the allele frequency (="gene frequency") for this mutation is about
- A.
1 in 1000 (0.1%)
- B.
1 in 400 (0.25%)
- C.
1 in 50 (2 %)
- D.
1 in 100 (1%)
- E.
1 in 200 (0.5%)
Correct Answer
D. 1 in 100 (1%)Explanation
The genetic screening of 200 people showed that there were two heterozygotes and one homozygote for the three-base pair deletion that causes cystic fibrosis. Since there were a total of three individuals out of 200 who carried this mutation, the allele frequency for this mutation is 3/200 or 1.5%. When expressed as "1 in X," this would be approximately 1 in 100 or 1%.Rate this question:
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- 13.
Imagine a species of Giraffes living on the savanna in Africa. The overall size of these varies as expected for a quantitative trait. The smallest giraffes have difficulty surviving, because they cannot reach the leafs on the trees that this species feed on. The largest giraffes have difficulty growing muscle large enough to move the massive bones needed for supporting this size of an animal. Therefore, the giraffes closest to the average size stand the best chance of surviving and reproducing. This is an example of which special concept?
- A.
Stabilizing selection
- B.
Disruptive selection
- C.
Directional selection
- D.
Founder effect
- E.
Genetic drift
Correct Answer
A. Stabilizing selectionExplanation
The given scenario describes stabilizing selection. Stabilizing selection occurs when individuals with average or intermediate traits have a higher fitness compared to individuals with extreme traits. In this case, the giraffes closest to the average size have the best chance of survival and reproduction because they can reach the leaves on trees and move their bones efficiently. The smallest and largest giraffes face difficulties in these aspects, leading to lower fitness. Therefore, stabilizing selection favors the maintenance of the average size within the giraffe population.Rate this question:
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- 14.
If you have high cholesterol, you may consider taking statins to help lowerthe levels. If you have desirable alleles in both the cholesteryl ester transfer protein and multidrug resistance transporter genes, the statin Fluvostatin will work well. However, if you have only undesirable alleles in both genes you will want to avoid Fluvostatin. If you have a mixture of desirable and undesirable alleles, then the number of each will determine the outcome. This description best fit which of the following concepts?
- A.
Assortative mating
- B.
Allele sharing
- C.
Additive effects
- D.
Low heritability
- E.
Anticipation
Correct Answer
C. Additive effectsExplanation
The concept that best fits the given description is "additive effects." This is because the outcome of taking the statin Fluvostatin is determined by the combination of desirable and undesirable alleles in both the cholesteryl ester transfer protein and multidrug resistance transporter genes. The effect of each allele is added together to determine the overall outcome. If a person has only undesirable alleles, the statin may not work well for them, while if they have desirable alleles, it will work well. If there is a mixture of desirable and undesirable alleles, the number of each will determine the overall outcome.Rate this question:
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- 15.
A syndrome is known to cause excessive height ,reduced IQ, and the cells exhibit 2 Barr bodies. Which karyotype is compatible with the above description?
- A.
45X
- B.
46XX
- C.
47XXX
- D.
47XXY
- E.
47XYY
Correct Answer
C. 47XXXExplanation
The karyotype 47XXX is compatible with the given description because it involves three X chromosomes, which is associated with excessive height and reduced IQ. Additionally, the presence of three X chromosomes leads to the formation of two Barr bodies in the cells, which is consistent with the description provided.Rate this question:
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- 16.
The BCR-ABL gene is involved in causing:
- A.
Alzheimer in Down syndrome
- B.
The specific sound of the cry in Cri-du-Chat
- C.
Polydactyly in Patau syndrome
- D.
Cell growth in leukemias
- E.
Hyperactivity in XYY syndrome
Correct Answer
D. Cell growth in leukemiasExplanation
The BCR-ABL gene is a fusion gene that results from a specific chromosomal translocation in certain types of leukemia, particularly chronic myeloid leukemia (CML). This gene produces a protein that has uncontrolled tyrosine kinase activity, leading to excessive cell growth and proliferation. This abnormal cell growth is a hallmark of leukemias, where the unregulated production of immature white blood cells disrupts the normal functioning of the bone marrow and immune system.Rate this question:
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