Chapter 11.2-11.3

What is the difference between phenotype and genotype?

The phenotype is the organism's physical appearance and the genotype is a combination of inherited alleles.

Define homozygous.

Genotype that has 2 dominant OR recessive alleles (PP or pp).

Define heterozygous.

Genotype that has one recessive and one dominant (Pp).

Define probability.

The mathematical chance that something will happen. It determines phenotypic ratios in offspring.

How many alleles does a gene have?

A gene has 2 alleles.

Define a punnett square.

It is a table that organizes all the possible genotype combinations of offspring from particular parents.

Who was Thomas Hunt Morgan?

He was a geneticist from the early 1900s who used fruit flies for genetic experiments, which was ideal because they produced plenty of offspring.

What were the conclusions drawn from Thomas Hunt Morgan's experiments with fruit flies?

The conclusions drawn from these were that Mendel's principles applied to most traits in most organisms.

Define incomplete dominance.

This is when a heterozygote has an immediate phenotype between that of either homozygote (the traits associated with each parent's genotype blend together).

What is an example of incomplete dominance in plants?

An example of incomplete dominance in plants is the snapdragon flower (red x white \= pink).

What is an example of incomplete dominance in humans?

An example of incomplete dominance in humans is sickle cell anemia, where red blood cells are sickle-shaped. A heterozygote has a milder sickle cell trait.

Define codominance.

When organisms have two different alleles of a gene and both phenotypes show at the same time.

What are some examples of codominance in animals?

Some examples of codominance in animals are roan cows (red x white \= white with red spots) and tabby cats (black x orange \= orange with black stripes).

What are some examples of codominance in humans?

Some examples of codominance in humans are ABO blood groups (AB blood type is an example of codominance).

True or false: Traits in which there are more than 2 alleles that determine a gene can occur ("multiple alleles").

True.

What are some examples of traits that are determined by more than 2 alleles ("multiple alleles")?

Some examples of traits that are determined by more than 2 alleles are animal fur color (4 different alleles) and human ABO blood types (3 alleles).

Define what a polygenic trait is.

It is an inherited trait that is determined by more than one gene.

What are some examples of polygenic traits?

Some examples of polygenic traits include eye color in humans that have at least 3 different genes with multiple alleles and parakeet feather color.

True or false: Environment will also influence polygenic traits; phenotype is controlled by both environment and genes.

True.

What polygenic traits on humans are affected by environment?

Skin color, height, weight, eye color, intelligence, and behaviors.