Biology 9.1: Introduction to Genetics

What is a phenotype?

• The expression of a trait; physical appearance.

• refers to the genes of an individual

• An organism that has the same genes for a trait (ex. TT or tt)

• the passing of traits from parent to offspring

What does heterozygous mean?

• An organism that has the same genes for a trait (TT or tt)
• An organism that has different genes for a trait (Tt)
• When neither gene is fully dominant; offspring is a mixture of both
• the different forms of a trait (hair color--> brown, blonde, red

An allele whose trait only shows up when no dominant allele is present.

• hidden allele
• dominant allele
• recessive allele
• present allele

An allele whose trait always shows up in the organism when the allele is present.

• recessive allele
• dominant allele
• hidden allele
• present allele

having two of the same genes for the trait (sometimes called purebred).

• homozygous
• hetrozygous
• protein
• chromosome

A single piece of coiled DNA found in the cells; contains genes that encode traits.

• gene
• chromosome
• trait
• DNA

What characteristic would a child not inherit from parents?

• freckles
• eye color
• hair style
• dimples

R=round seed
r=wrinkled seed.
Cross a homozygous round with a wrinkled. Which statement predicts the results?

• offspring will be Rr
• offspring will be RR
• round seeds will be recessive to wrinkled
• Wrinkled will be observed in half of offspring

W=white hair
w= non-white hair
If you cross a horse with WW and a horse with ww what fraction of the offspring would be expected to have white hair?

• none
• 3/4
• 1/2
• all

Pea plants can have green or yellow seeds. In a pea plant that is heterozygous for seed color, the allele for yellow seeds masks the effects of the allele of green seeds. Which of the following terms best describes the allele for yellow seeds?

• codominant
• recessive
• dominant
• sex-linked