Question 1

Which of the following best describes the maternal effect in genetics?

Accepted Answer

The phenotype of the offspring is determined by the genotype of the mother, regardless of the offspring's own genotype.

Question 2

A cross is made between a dextral (right-coiling, DD) female snail and a sinistral (left-coiling, dd) male snail. What will be the phenotype of the F1 offspring, and why?

Accepted Answer

All dextral, because the mother's genotype determines the offspring's phenotype due to the maternal effect.

Question 3

Which of the following is a key difference between maternal effect and cytoplasmic (extranuclear) inheritance?

Accepted Answer

Maternal effect is determined by gene products in the egg, while cytoplasmic inheritance is determined by organelle DNA.

Question 4

Which of the following best explains why calico cats display a mosaic pattern of fur color?

Accepted Answer

Random X-inactivation in each cell leads to different alleles being expressed in different patches of skin.

Question 5

A woman with genotype $$X^B X^b ($$where $$B = $$black, $$b = $$orange) mates with an orange male ($$X^b Y). $$What is the expected ratio of offspring phenotypes?

Accepted Answer

1 calico female, 1 black male, 1 orange male, 1 orange female

Question 6

Which of the following statements about X-inactivation in mammals is correct?

Accepted Answer

One X chromosome in each somatic cell of females is randomly inactivated, forming a Barr body.

Question 7

A human with the genotype $$XXXY$$ will have how many Barr bodies in each somatic cell?

Accepted Answer

2

Question 8

Which of the following is a feature of mitochondrial DNA (mtDNA) in humans?

Accepted Answer

It is inherited almost exclusively from the mother.

Question 9

A woman with a mitochondrial disease has children with a healthy man. What is the probability that her children will inherit the disease?

Accepted Answer

All of her children will inherit the disease.

Question 10

Which of the following best describes the concept of 'threshold effect' in mitochondrial diseases?

Accepted Answer

Symptoms appear only when the proportion of mutant mitochondria exceeds a certain level in cells.

Question 11

Which of the following is an example of epigenetic inheritance?

Accepted Answer

DNA methylation patterns that silence gene expression and are passed to daughter cells.

Question 12

Which of the following statements about cytoplasmic inheritance is correct?

Accepted Answer

It is usually, but not always, inherited from the mother because the egg contributes most of the cytoplasm.

Question 13

A plant with variegated leaves (green and white sectors) is crossed with a plant with all green leaves. All offspring have variegated leaves. What is the most likely explanation?

Accepted Answer

The trait is due to cytoplasmic inheritance of chloroplasts from the variegated parent.

Question 14

Which of the following mechanisms is NOT a form of non-Mendelian inheritance?

Accepted Answer

Autosomal dominant inheritance

Question 15

Which of the following best explains why some X-linked genes escape inactivation in humans?

Accepted Answer

They are located in pseudoautosomal regions shared with the Y chromosome.

Question 16

In a certain plant species, chloroplast DNA is inherited paternally. If a green-leafed male is crossed with a white-leafed female, what will be the phenotype of the offspring?

Accepted Answer

All offspring will have green leaves.

Question 17

Which of the following is a real-world example of a human disease caused by a mutation in mitochondrial DNA?

Accepted Answer

Leber's hereditary optic neuropathy (LHON)

Question 18

Which equation would you use to determine the number of Barr bodies in a human somatic cell?

Accepted Answer

$$	ext{Number of Barr bodies} = 	ext{Number of X chromosomes} - 1$$

Question 19

Which of the following statements about dosage compensation is correct?

Accepted Answer

It ensures equal expression of X-linked genes in males and females.

Question 20

A woman is heteroplasmic for a mitochondrial mutation (some mitochondria are mutant, some are normal). Which of the following best predicts the severity of disease in her children?

Accepted Answer

The proportion of mutant mitochondria inherited by each child.

Non-Mendelian Inheritance: Mechanisms and Examples

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