Chapter 14: Mendel and the Gene Idea

Question 1

What is true-breeding?

Answer 1

Completely homozygous parents passing on

Question 2

What is hybridization?

Answer 2

Cross between two true-breeding varieties

Question 3

Versions of genes are called _______.

Answer 3

Alleles

Question 4

What is a locus?

Answer 4

Area of chromosome that holds the gene

Question 5

What is the genotype?

Answer 5

The actual genetic ratio

Question 6

What is the phenotype?

Answer 6

The visual ratio

Question 7

What is the Law of Segregation?

Answer 7

When heritable traits are hidden and then reappear

When a heterozygous crosses with another heterozygous

(When two alleles in a pair segregated into different gametes during gamete formation)

Question 8

What is the law of independent assortment?

Answer 8

Hereditary alleles assort randomly during gamete production

Alleles assort independently of each other, such as round/wrinkled vs yellow/green

Question 9

What is testcrossing?

Answer 9

Do either:

PP x pp
Pp x pp

This is to figure out if the dominant gene is homozygous or heterozygous

Question 10

To determine the genotype of a round pea plant it should be crossed with ____________________.

Answer 10

Homozygous recessive plant

Question 11

What is a dihybrid cross?

Answer 11

Looking at two traits simultaneously

Eg, peas

Question 12

What is incomplete dominance?

Answer 12

Neither gene is dominant, but there is a blend.

Pink is considered the “intermediate phenotype”

Red + white = pink

Question 13

What is codominance?

Answer 13

Neither gene is dominant, but there is a mixture of the two.

Black + white = black and white spots

Question 14

For incomplete dominance and codominance, how do you write the punnet squares?

Answer 14

Red: C^r
White: C^w
Pink: C^r C^w

Question 15

Which of the following represents a gamete that the dihybrid plant (YyRr) could form?

A. Yy
B. Rr
C. YR
D. YyRr

Answer 15

C. YR

Because YyRr would give one trait from the mother and one trait from the father, which would be:

YR
Yr
yR
yr

Question 16

What are multiple alleles and what’s an example of them?

Answer 16

3 or more alleles for a specific gene

Eg, blood groups

Question 17

What are the genotypes for blood group A, B, AB, and O?

Answer 17

A - IA IA or IA i

B - IB IB or IB i

AB - IA IB

O - ii

Question 18

True or false:

The blood type of a child who’s parents blood types are A and B could be A, B, AB, or O.

Answer 18

True

Do a punnet square

Question 19

What is epistasis?

Answer 19

When one gene affects the expression of another gene

Gene 1: lab fur colour
Gene 2: permission of pigment

Question 20

What does this mean:

The gene for pigment deposition is epistatic to the gene for lab colour.

Answer 20

The gene for pigment disposition is more important (dominant) than the gene for fur colour

Question 21

What is pedigree analysis?

Answer 21

Chart of traits in humans

Question 22

What is significant about having a recessive disorder?

Answer 22

If you’re heterozygous for a recessive disorder, you will not have that disorder. If you are heterozygous you only “carry” it.

DD = you do not have the disorder 
Dd = you carry the disorder 
dd = you have the disorder

Question 23

What is significant about having a dominant disorder?

Answer 23

If you are heterozygous for a dominant disorder, you will have that disorder.

DD = you have the disorder 
Dd = you have the disorder 
dd = you do not have the disorder