Genetics review

An organism's phenotype describes its __________.

• genetic makeup
• physical appearance

What do you call a section of DNA that codes for a specific trait?

• nucleus
• chromosome
• gene
• DNA

How many chromosomes are found in human egg and sperm cells?

• 20
• 23
• 26
• 46

__________ worked with pea plants to prove that traits are passed from parent to offspring.

• Reginald Punnett
• Gregor Mendel

An organism's genotype describes its __________.

• genetic makeup
• physical appearance

A dominant trait shows up __________.

• only when two dominant alleles are present
• only when one dominant allele is present
• when at least one recessive allele is present
• when at least one dominant allele is present

A recessive trait only shows up when __________.

• two dominant alleles are present
• one dominant allele is present
• two recessive alleles are present
• at least one dominant allele is present

If you cross two parents, both with genotype Bb, what percentage of children will have brown eyes?

• 25%
• 50%
• 75%
• 100%

Purebred is another word for __________, while hybrid is another word for __________.

• dominant; recessive
• recessive; dominant
• homozygous; heterozygous
• heterozygous; homozygous

The two different forms of a gene are called _________.

• zygotes
• traits
• phenotypes
• alleles