Genetics Review (pt 1)

Suppose the brown allele for eye color (B) is completely dominant over the blue allele for eye color (b). What is the probability that two heterozygous parents will have a child with blue eyes?

• 100%

• 75%

• 50%

• 25%

• 0%

In drosophila (fruit flies), eye colour is sex-linked and red eye color is dominant to white eye color. Which of the following are not possible in a cross between a red-eyed male and a heterozygous female?

• Red-eyed male

• Carrier female

• White-eyed male

• Homozygous white-eyed female

An extra finger in humans is rare but is due to a dominant gene. When one parent has five fingers and the other parent is heterozygous for the extra finger trait, what is the probability that their child will have a normal number of fingers?

• 100%

• 75%

• 50%

• 25%

• 0%

When crossing a homozygous recessive (rr) with a heterozygote (Rr), what is the chance of getting an offspring with the homozygous recessive (rr) phenotype?

• 100%

• 75%

• 50%

• 25%

• 0%

Long radishes crossed with round radishes result in all oval radishes. This type of inheritance is:

• Incomplete dominance.

• Complete dominance (Simple dominant-recessive inheritance).

• Co-dominance.

• Multiple alleles.

If two white sheep produce a black offspring, the parent’s genotypes for color must be:

• Heterozygous.

• Homozygous white.

• Homozygous black

• Not enough information was given

If an offspring is said to be homozygous recessive, which of the following could be its genotype?

• RW

• ff

• TT

• Rr

What does the notation TT (for tall pea plants ) mean to geneticists?

• The pea plant has two dominant alleles

• The pea plant has two recessive alleles

• The pea plant has one dominant and one recessive allele

• The pea plant has at least one dominant allele

The different (alternate) forms of a gene are called...

• alleles

• traits

• chromosomes

How do geneticists use pedigrees?

• to create genetic crosses

• to trace the inheritance of traits over generations of families

• to make identical copies of segments of DNA

• to prove that sex-linked traits are caused by codominant alleles