Unit 5 Review: How Traits Pass Down

Lesson Goal

Bring the four Unit 5 lessons together, check which parts hold and which need a second read, and finish by writing about why a dominant trait isn't necessarily the most common.

Key Concepts

Every question here is tied to one of the four lessons and the hint says which one, so a wrong answer is directions to the right page and not a mark against the student.

The written question is the real test of whether the unit landed. The key idea is that dominant describes which allele shows when two are present, and says nothing about how many people carry it.

Where Students Get Stuck

🚨 Reading a Punnett square as a promise. It gives the chance for each child and not the count, so two carriers can have four children and none affected.

Treating carrying an allele as having the disorder. A carrier has one copy and usually no symptoms, and that's a different thing.

Key Vocabulary

Allele

One of the different forms of a gene for a trait. You get one from each parent.

Dominant

The allele that shows when two different alleles are present.

Recessive

The allele that stays hidden when a dominant allele is present.

Genotype

The allele letters an organism carries, like TT or Tt.

Phenotype

What the alleles look like in the organism, like tall or short.

Punnett square

A grid that lays out every pairing a cross can make, so you can read the chances.

Incomplete dominance

A pattern where neither allele fully covers the other, so a plant with one of each shows a look in between.

Polygenic inheritance

A pattern where many gene pairs act together on one trait, giving a smooth range.

Sex-linked gene

A gene that sits on a sex chromosome, usually the X.

Carrier

A person who has one copy of a recessive allele and usually shows no symptoms but can pass it on.

Pedigree

A chart of a family that shows who has a trait.

Genome

The whole set of an organism's genes.