Chapter 12 - Mendian Genetics

Question 1

Three features of Mendel’s research that were critical to its success

Answer 1

1. Chose to use the garden pea plant.
2. Focused on easily identifiable parts.
3. Bred plants that were true-breeding plants

Question 2

Mendel’s 3 important ideas

Answer 2

1. The adult plants carry a pair of factors that govern the inheritance of each trait
2. If an individual’s pair of factors are different, then one factor is dominant over the other
3. The pairs of factors that control a character segregate as gametes are formed; half the gametes carry one factor, and the other half carry the other factor.
   Known as principle of Segregation

Question 3

F2 always shows a 3:1 ratio because?

Answer 3

Principle of Segregation

Question 4

Why will a monohybrid always give a 3:1 ratio?

Answer 4

Principle of Segregation

Question 5

Testcross

Answer 5

Used to determine the unknown genotype of a dominant phenotype.
When performing a testcross, brown eyes must be crossed with blue eyes.

Question 6

Another important idea by Mendel

Answer 6

4. Each pair of alleles segregated independently of each other during gamete formation.
   This is known as Principle of Independent Assortment

Question 7

Dihybrid cross

Answer 7

A cross between two parents who are heterozygous for two different traits
AaBb x AaBb

Question 8

Why does the dihybrid cross always show a 9:3:3:1 ratio?

Answer 8

Principle of Independent Assortment

Question 9

Incomplete Dominance

Answer 9

In this trait, there are three genotypes and three phenotypes.
When completing a monohybrid cross, the phenotypic ratio will not be 3:1, instead it will be 1:2:1

Question 10

Epistasis

Answer 10

In this type of inheritance, one trait is determined by two genes in which one gene controls the expression of the second gene.

Question 11

Polygenic Inheritance

Answer 11

There are traits that are controlled by three or more genes, known as polygenes

Question 12

Polygenes

Answer 12

Control traits that are multifactorial, meaning the traits are influenced by the environment.

Question 13

Pleiotropic Inheritance

Answer 13

Sometimes a person can have one gene that influences multiple unrelated traits

Question 14

Why are traits passed on from the mother?

Answer 14

Chloroplasts are found within the cytoplasm of the egg

• egg provides cytoplasm, organelles and nucleus
• Hence the maternal inheritance

Question 15

Mutations in human mitochondrial genes

Answer 15

Can cause a variety of rare diseases