Question 1

Which of the following best explains why Mendel's choice of garden peas contributed to his success in discovering the basic principles of heredity?

Accepted Answer

Garden peas are diploid, sexually reproducing, easy to cultivate, produce many progeny, and have different pure-breeding strains available.

Question 2

Mendel’s Law of Segregation states that:

Accepted Answer

Each individual has two alleles for each trait, and these alleles separate randomly into gametes, so each gamete receives one allele.

Question 3

In a monohybrid cross between two heterozygous pea plants ($Aa 	imes Aa$), what is the expected genotypic ratio in the F2 generation?

Accepted Answer

$1:2:1$ (AA:Aa:aa)

Question 4

Which scenario best illustrates the concept of blending inheritance, and why did Mendel’s results contradict it?

Accepted Answer

Offspring always show traits intermediate between parents, but Mendel observed traits reappearing unchanged after several generations.

Question 5

A testcross is performed to determine the genotype of a tall pea plant. Which cross would you use, and what result would indicate the plant is heterozygous?

Accepted Answer

Cross the tall plant with a homozygous recessive plant; if any offspring are short, the tall plant is heterozygous.

Question 6

In a dihybrid cross ($RrYy 	imes RrYy$), what is the expected phenotypic ratio in the F2 generation according to Mendel’s Law of Independent Assortment?

Accepted Answer

$9:3:3:1$

Question 7

If you roll a die twice, what is the probability of getting a '4' both times? Use the multiplication rule for independent events.

Accepted Answer

$\frac{1}{36}$

Question 8

A cross is made between $AaBbccDdEe$ and $AaBbCcddEe$. What is the probability of obtaining an offspring with genotype $aabbccddee$?

Accepted Answer

$\frac{1}{256}$

Question 9

Which of the following is true about autosomal recessive traits in human pedigrees?

Accepted Answer

They often skip generations and appear equally in both sexes.

Question 10

A pedigree shows a trait appearing in every generation and affecting both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 11

Which equation is used to calculate the chi-square ($\chi^2$) statistic in genetics for evaluating the role of chance in observed vs. expected results?

Accepted Answer

$\chi^2 = \sum \frac{(Observed - Expected)^2}{Expected}$

Question 12

Which of the following human diseases is inherited as an autosomal recessive trait?

Accepted Answer

Cystic fibrosis

Question 13

If two parents are both heterozygous for albinism ($Aa$), what is the probability that their child will be albino?

Accepted Answer

$\frac{1}{4}$

Question 14

Which statement best describes the relationship between genotype and phenotype?

Accepted Answer

Phenotype is the manifestation or appearance of a character, resulting from the interaction of genotype and environment.

Question 15

In a cross between $RrYy$ (round yellow) and $rryy$ (wrinkled green) pea plants, what is the probability of obtaining a plant with genotype $RrYy$?

Accepted Answer

$\frac{1}{4}$

Question 16

Which of the following is NOT a reason Mendel’s work was initially ignored by the scientific community?

Accepted Answer

His paper was published in a relatively obscure journal.

Question 17

Which principle explains why alleles for different traits are inherited independently, provided the genes are on different chromosomes?

Accepted Answer

Principle of Independent Assortment

Question 18

A pedigree shows two unaffected parents having an affected child. What is the most likely inheritance pattern for the trait?

Accepted Answer

Autosomal recessive

Question 19

Which of the following is a representative dominant human trait?

Accepted Answer

Achondroplasia

Question 20

In a family pedigree, what does a half-shaded circle typically represent?

Accepted Answer

A heterozygous carrier female

Genetics Lecture 3: Mendelian Genetics and Alleles

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