Question 1

Which of the following best explains why Mendel's use of true-breeding pea plants was critical to his experiments on heredity?

Accepted Answer

True-breeding plants guaranteed that the parental generation was homozygous for the traits studied, so any variation in the F1 and F2 generations could be attributed to the segregation and assortment of alleles.

Question 2

In a monohybrid cross between two heterozygous pea plants (genotype $$Pp$$), what is the expected genotypic ratio among the F2 offspring?

Accepted Answer

$$1\;PP : 2\;Pp : 1\;pp$$

Question 3

A black Labrador (dominant black allele $$B) is $$crossed with a chocolate Labrador (recessive allele $$b). If $$the black Labrador is heterozygous, what proportion of the offspring are expected to be chocolate?

Accepted Answer

$$50\%$$

Question 4

Which of the following statements about Mendel’s principle of segregation is correct?

Accepted Answer

Each diploid organism possesses two alleles for a characteristic, and these alleles separate during gamete formation so that each gamete receives only one allele.

Question 5

A dihybrid cross between two pea plants heterozygous for seed color ($$Yy) $$and seed shape ($$Rr) $$produces which phenotypic ratio in the F2 generation, assuming independent assortment?

Accepted Answer

$$9:3:3:1$$

Question 6

If a human pedigree shows a trait present in every generation and affected individuals always have at least one affected parent, what is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 7

Given the following observed and expected values for a genetic cross: Observed = 69 purple, 31 white; Expected (3:1 ratio) = 75 purple, 25 white. Calculate the chi-square value ($$\$$chi^2$$) using the formula $$\$$chi^2$$ = \sum \frac{$$(O-E)^2$$}{E}$$.

Accepted Answer

$$\$$chi^2$$ = 1.92$$

Question 8

In Drosophila, the allele for white eyes ($$w) is $$recessive to the wild-type allele ($$w^+). $$What is the expected phenotype of a fly with genotype $$w^+/w$$?

Accepted Answer

Wild-type eyes

Question 9

A plant breeder crosses two true-breeding pea plants, one with yellow-round seeds ($$YYRR) $$and one with green-wrinkled seeds ($$yyrr). $$What is the genotype of all F1 offspring?

Accepted Answer

$$YyRr$$

Question 10

How many different types of gametes can a diploid organism with $$n$$ pairs of chromosomes produce, assuming independent assortment and no crossing over?

Accepted Answer

$$2^n$$

Question 11

A pedigree shows two unaffected parents with an affected child. The trait is equally present in males and females. What is the most likely genotype of the parents?

Accepted Answer

Both parents are heterozygous carriers

Question 12

Which of the following best describes the difference between genotype and phenotype?

Accepted Answer

Genotype refers to the genetic makeup, while phenotype refers to the observable physical traits.

Question 13

If a human genetic disorder is caused by a recessive allele, which of the following is most likely true?

Accepted Answer

The disorder can skip generations, and unaffected parents can have affected children.

Question 14

A testcross is performed between a plant with an unknown genotype for a dominant trait and a homozygous recessive plant. If all offspring display the dominant phenotype, what is the genotype of the unknown parent?

Accepted Answer

Homozygous dominant

Question 15

Which of the following is a real-world example of a dominant human genetic disorder discussed in the lecture?

Accepted Answer

Huntington’s disease

Question 16

If a species has 4 pairs of homologous chromosomes, how many different gamete types can it produce due to independent assortment alone?

Accepted Answer

$$2^4 = 16$

Question 17

Which of the following best explains why the phenotypic consequences of segregation in diploid organisms are observed with a lag time of one generation?

Accepted Answer

Because the F1 generation is heterozygous and only the F2 generation reveals the segregation of alleles through the reappearance of the recessive phenotype.

Question 18

A chi-square test yields a $$P$$ value of $$0.2$$ when comparing observed and expected ratios in a genetic cross. What is the correct interpretation?

Accepted Answer

The deviation is likely due to chance, and the null hypothesis cannot be rejected.

Question 19

Which of the following statements about gene linkage is correct based on the lecture?

Accepted Answer

Genes located close together on the same chromosome tend to be inherited together, which is called gene linkage.

Basic Principles of Heredity: Mendelian Genetics and Human Inheritance

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