Review for Lecture 13.
1. In Mendel's F2 generation, one out of four plants had white flowers because
A) the trait is sex-linked
B) both parents were heterozygous purple
C) one parent was homozygous recessive
D) both parents were heterozygous white
2. In the F2 generation, the 3:1 ratio is really a disguised
A) 1:2:1
B) 2:1:1
C) 1:1:2
D) 4:0
E) 4:1
3. The ratio often referred to the Mendelian ratio is
A) 1:3:3:1
B) 9:7
C) 1:3:1
D) 1:1
E) 3:1
4. When Mendel crossed pure-breeding purple and white flowered pea plants, the
dominant to recessive ratio in the F1 generation was
A) 3:1
B) 4:0
C) 4:1
D) 4:0
E) 9:3:3:1
5. In Mendel's F2 generation of the purple and white flower crossing, the dominant to
recessive ratio was
A) 1:3:1
B) 3:1
C) 1:1
D) 9:7
E) 9:3:3:1
6. A individual who has two of the same allele is said to be
A) homozygous
B) heteromologous
C) homologous
D) heterozygous
E) diplozygous
7. Where two alternatives for a trait are tall and short, and tall is dominant, the genotype
of a heterozygous individual would be expressed
A) sS
B) ss
C) SS
D) Ss
E) tall
8. The appearance resulting from a given gene combination is referred to as the
A) genotype
B) phenotype
C) phototype
D) alleleotype
E) stereotype
9. Compared to previous geneticists, the unique characteristic of Mendel's work was
A) keeping records of numbers of different progeny
B) choosing the garden pea for his experiment
C) producing hybrids
D) studying more than one generation
E) crossing true-breeding plants
10. Where the two alternatives for a trait are broad and narrow, and broad is dominant,
the phenotype of a homozygous dominant individual would be expressed as
A) BB
B) nn
C) Bn
D) NN
E) broad
11. In garden peas, height is determined by a single gene with tall being dominate to
short. If two heterozygous plants are crossed, what proportion of the tall progeny will be
homozygous dominant?
A) 3/4
B) 2/3
C) 1/2
D) 1/3
E) 1/4
12. In the cross MMnn x mmNN, what proportion of the resulting F1 would be
homozygous dominant for both genes?
A) none
B) 1/16
C) 3/16
D) 9/16
E) all
13. In humans pointed eyebrows are dominant to smooth eyebrows and widow's peak
(downward pointed frontal hairline) is dominant to continuous hairline. What phenotypic
ratio would you expect in the offspring from a cross between an individual heterozygous
for both genes and an individual homozygous recessive for both genes?
A) 9:3:3:1
B) 9:3:4
C) 1:1:1:1
D) 1:2:1:2:4:2:1:2:1
E) 9:7
14. Hypertrichosis, hairiness of the pinna of the ear, is inherited as a Y-linked recessive in
humans. If a man with hypertrichosis marries a normal woman, what types of children
may they have?
A) All of their children of both sexes have hypertrichosis.
B) All the sons have hypertrichosis, but none of their daughters.
C) Half of their sons, but none of their daughters will have hypertrichosis.
D) All the daughters have hypertrichosis, but none of their sons.
E) None of their children have hypertrichosis.
15. The model for the dihybrid cross of heterozygotes predicts a phenotypic ratio of
9:3:3:1.
A) True
B) False
16. Epistasis is a genetic condition in which certain alleles of one locus can alter the
expression of alleles of a different locus.
A) True
B) False
17. The genotypes of a husband and wife are IAIB x IAi. Among the blood types of their
children, how many different genotypes and phenotypes are possible?
A) 2 genotypes; 3 phenotypes
B) 3 genotypes; 4 phenotypes
C) 4 genotypes; 4 phenotypes
D) 3 genotypes; 3 phenotypes
E) 4 genotypes; 3 phenotypes
18. A trait caused by a recessive autosomal allele will result in a pedigree that shows
affected individuals having at least one affected parent.
A) True
B) False
19. Down syndrome results from:
A) the absence of one chromosome in position 21
B) the presence of an extra chromosome in position 21
C) the absence of both chromosomes in position 21
D) crossing over on the chromosomes in position 21
E) none of the above
20. Describe a situation involving incomplete dominance – see your tectbook. What is
incomplete dominance?