Genetics (SI7)

In a certain breed of cats, having black hair is the result of two dominant alleles for hair color (HH). The heterozygous genotype (Hh) produces a cat that has black and white spots. Having two recessive (hh) genes results in a white-haired cat. The Punnett square shows the results of a cross between which two cats?

• a black cat and a spotted cat
• a spotted cat and a white cat
• two spotted cats
• two black cats

Fruit flies can either have a brown body or a black body. The allele for a brown body (B) is dominant to the allele for a black body (b). A brown fruit fly was crossed with a black fruit fly as shown. What is the probability of a resulting offspring being brown?

• 1
• 0.25
• 0.5
• 0.75

Freckles (F) are a dominant trait. The Punnett square for a non-freckled parent and a homozygous freckled parent is shown. What is the probability that their children will have freckles?

• 1
• 0.75
• 0.5
• 0

Examine the pedigree shown. If curly hair (C) is a dominant trait, what are the genotypes of the parents in the pedigree?

• Both parents are heterozygous (Cc) for the curly hair trait.
• One parent is heterozygous (Cc) for the curly hair trait, and the other parent is homozygous for the curly hair trait (CC).
• Both parents are homozygous (CC) for the curly hair trait.
• One parent is homozygous for the curly hair trait (CC), and the other parent is homozygous for non-curly hair (cc).

The pedigree shows the inheritance of sickle-cell anemia, a genetic disease, in a particular family. The shaded squares represent males with sickle-cell anemia. The shaded circles represent females with sickle-cell anemia. Which of the following is true about the individual highlighted in red?

• This individual has a grandfather with sickle-cell anemia.
• This individual has sickle-cell anemia.
• This individual has a grandmother with sickle-cell anemia.
• This individual has two parents with sickle-cell anemia.

In pea plants, the allele for tallness (T) is dominant to the allele for shortness (t). In the cross between a tall pea plant and a short pea plant shown, what is the probability that the resulting offspring will be tall?

• 0.5
• 0.75
• 0.25
• 1

The pedigree chart shows the inheritance of sickle-cell anemia, a genetic disease, in a particular family. The shaded symbols represent individuals with sickle-cell anemia. The father in generation I has sickle-cell anemia. How many of his children have sickle-cell anemia?

• 2
• 4
• 1
• 3

The pedigree chart shows the inheritance of sickle-cell anemia in a particular family. The shaded symbols represent individuals with sickle-cell anemia. Sickle-cell anemia is a genetic disorder of the blood in which the shape of red blood cells is distorted, resulting in a variety of health problems. The allele for normal blood cell production (H) is dominant to the allele for sickle cell production (h). Which of the following is true about the parents highlighted in red?

• Each parent is heterozygous (Hh) for sickle-cell anemia.
• The father is homozygous dominant (HH) and the mother is homozygous recessive (hh).
• Each parent is homozygous recessive (hh) for sickle-cell anemia.
• Each parent is homozygous dominant (HH) for sickle-cell anemia.

If night blindness is a recessive trait, what should the phenotype of the couple's fourth child be?

• The child will have normal vision.

• The child will be night blind.

• The child could be night blind or have normal vision.

• The child will develop night blindness later in life.

Organisms typically have more than one form of each gene. If one form can mask the appearance of another form, that form is considered _______ the other form.

• dominant over
• worse than
• recessive to
• better than