Q: If a plant with genotype $$Tt ($$tall) is self-fertilized, what is the probability that three out of four offspring will be tall? (Use binomial probability.)

$$4 \times (\frac{3}{4})^3$ \times (\frac{1}{4})^1$ = 27/64$$

Q: A cross between two heterozygous purple-flowered pea plants ($$Pp \times Pp) $$produces 120 offspring. How many are expected to have white flowers?

$$120 \times \frac{1}{4} = 30$$

Question 1

Which of the following best describes Mendel’s law of segregation?

Accepted Answer

Alleles for a trait separate during gamete formation, and each gamete receives only one allele.

Question 2

A pea plant with genotype $$Gg is $$self-fertilized. What is the probability that a single offspring will have green seeds (recessive phenotype)?

Accepted Answer

$$\frac{1}{4}$$

Question 3

In a dihybrid cross between two $$RrGg$$ pea plants, what is the expected phenotypic ratio of round yellow : round green : wrinkled yellow : wrinkled green seeds in the F2 generation?

Accepted Answer

$$9:3:3:1$$

Question 4

Which of the following experimental innovations was NOT a critical feature of Mendel’s success?

Accepted Answer

Selection of traits with multiple intermediate phenotypes

Question 5

A test cross is performed between a plant with an unknown genotype showing the dominant phenotype and a homozygous recessive plant. If the unknown plant is heterozygous, what ratio of phenotypes is expected in the offspring?

Accepted Answer

$$1:1 ($$dominant:recessive)

Question 6

Which molecular explanation best describes why wrinkled peas appear in Mendel’s experiments?

Accepted Answer

A loss-of-function mutation in the Sbe1 gene prevents the production of amylopectin, causing seeds to retain water and wrinkle as they dry.

Question 7

If a plant with genotype $$Tt ($$tall) is self-fertilized, what is the probability that three out of four offspring will be tall? (Use binomial probability.)

Accepted Answer

$$4 	imes (\frac{3}{4})^3$ 	imes (\frac{1}{4})^1$ = 27/64$$

Question 8

Which of the following is a key feature of autosomal dominant inheritance in human pedigrees?

Accepted Answer

Every affected individual has at least one affected parent.

Question 9

A cross between two heterozygous purple-flowered pea plants ($$Pp 	imes Pp) $$produces 120 offspring. How many are expected to have white flowers?

Accepted Answer

$$120 	imes \frac{1}{4} = 30$$

Question 10

Which probability rule should be used to calculate the likelihood of obtaining a round, yellow seed from a dihybrid cross ($$RrGg 	imes RrGg$$)?

Accepted Answer

Product rule

Question 11

In a pedigree, a trait appears in both males and females, skips generations, and affected individuals are often born to unaffected parents. What is the most likely mode of inheritance?

Accepted Answer

Autosomal recessive

Question 12

A chi-square test is performed on a monohybrid cross with observed values of 5474 round and 1850 wrinkled seeds. The expected ratio is $$3:1. $$What is the degrees of freedom for this test?

Accepted Answer

$$1$$

Question 13

Which of the following statements about Mendel’s experimental approach is FALSE?

Accepted Answer

He used traits with continuous variation.

Question 14

What is the probability that, in a family with four children, all will be girls? (Assume equal probability for boys and girls.)

Accepted Answer

$$(\frac{1}{2})^4$ = \frac{1}{16}$$

Question 15

Which gene is responsible for the tall versus short phenotype in Mendel’s pea plants, and what is its molecular function?

Accepted Answer

Le gene; encodes giberellin 3β-hydroxylase, involved in plant growth hormone production

Question 16

If a yellow-seeded pea plant is known to be either $$GG or$$ $$Gg$$, and it is crossed with a green-seeded plant ($$gg$$), what proportion of yellow-seeded offspring would indicate the yellow parent is heterozygous?

Accepted Answer

$$0.5$$

Question 17

Which of the following best explains why the blending theory of inheritance was rejected?

Accepted Answer

Recessive traits reappeared unchanged in the F2 generation.

Question 18

How many different types of gametes can be produced by a plant with genotype $$AaBbCc$$?

Accepted Answer

$$2^3 = 8$

Question 19

Which of the following is TRUE regarding the molecular basis of Mendel’s traits?

Accepted Answer

Dominant alleles are usually functional, while recessive alleles are often loss-of-function mutations.

Transmission Genetics: Mendel’s Principles and Modern Applications

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