science beginner 10 sample questions

Genetics MCQ Practice Test

Heredity and genetic material

Q1. The phenomenon in which an allele at one locus masks or modifies the expression of an allele at a different locus is called:

Explanation: Epistasis is interaction between genes at different loci: for example, in Labrador retrievers a pigment-deposition locus masks the color locus. Hitchhiking is linkage to a selected allele, and position effects involve chromosomal rearrangements.

Q2. In Saccharomyces cerevisiae, meiotic recombination is initiated when which protein creates programmed double-strand breaks in DNA?

Explanation: Spo11, related to type II topoisomerases, uses a catalytic tyrosine to cleave DNA and stays covalently attached to the 5' ends; the breaks are then resected by the MRX complex and Exo1/Sgs1 and repaired as crossovers or non-crossovers.

Q3. The phenomenon in which a gene is expressed in a specific tissue type due to the presence of a specific transcription factor is known as

Explanation: The presence of specific transcription factors in certain tissue types can trigger the expression of genes through the interaction with cis-regulatory elements, leading to tissue-specific expression of the gene.

Q4. The phenomenon of gene conversion in meiosis is most closely associated with which of the following recombination mechanisms?

Explanation: Gene conversion is a type of recombination that results in the exchange of genetic information between identical or nearly identical sequences of DNA. It is a key mechanism by which genetic diversity is generated during meiosis, and is most closely associated with gene conversion.

Q5. In yeast, the gene Õ is a transcriptional activator of the GAL1 gene, which encodes a protein involved in galactose metabolism. The Õ gene contains a specific DNA sequence that is recognized by the Gal4 protein, which binds to it and recruits other transcription factors to activate gene expression. What is the term for this specific DNA sequence recognized by the Gal4 protein?

Explanation: The UAS (Upstream Activating Sequence) is a specific DNA sequence recognized by the Gal4 protein, which binds to it and recruits other transcription factors to activate gene expression of the GAL1 gene. This is an example of a specific DNA sequence acting as a cis-regulatory element to control gene expression in response to environmental cues.

Q6. The phenomenon of gene conversion, where a non-sister chromatid serves as a template for repair, is most commonly observed in the following type of meiotic recombination event:

Explanation: Gene conversion is a hallmark of double-strand break repair in meiosis, particularly in the context of Holliday junction intermediates. This process allows for the exchange of genetic material between non-sister chromatids, resulting in gene conversion events.

Q7. In the context of β-globin gene regulation, the HbF (β-globin) to HbA (β-globin) transition is primarily controlled by the interaction of which two transcription factors?

Explanation: The HbF to HbA transition is a key developmental switch in hemoglobin expression, with GATA-1 and KLF1 playing crucial roles in regulating the β-globin gene. GATA-1 acts as a transcriptional activator, while KLF1 functions as a repressor, facilitating the repression of HbF and the activation of HbA.

Q8. The founder effect — a small group leaving a population to establish a new one with only a fraction of its genetic variation — is a special case of which evolutionary force?

Explanation: The founder effect is a random shift in allele frequencies caused by sampling a small subgroup — which is precisely genetic drift. Hitchhiking (the old key) is the selection-driven spread of a neutral allele linked to a beneficial one, a different mechanism the old explanation conflated with founders.

Q9. The phenomenon of gene conversion, where a non-sister chromatid of a homologous chromosome is used as a template for repair, is most accurately described by which of the following mechanisms?

Explanation: Gene conversion is a process that occurs during meiosis, where a non-sister chromatid of a homologous chromosome is used as a template for repair. This can result in the exchange of genetic information between the two chromosomes, leading to changes in the genetic sequence. Non-crossover gene conversion is the most accurate description of this phenomenon, as it involves the use of a non-sister chromatid without the exchange of genetic material between the two chromosomes.

Q10. Gene conversion is best explained by which underlying cellular process?

Explanation: During meiotic recombination, a heteroduplex region can form between homologous chromosomes; when mismatch repair uses one strand as the template, one allele is "converted" to the sequence of the other — gene conversion.

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Genetics MCQ Practice Test | Mind Hustle