Review - Genetics and Modes of Gene action

Question 1

In terms of breeding, how do you define a gene?

Answer 1

Basic unit of heredity.

Question 2

A chromosome is:

Answer 2

A long strand of DNA and associated proteins present in the nucleus of all cells.

Question 3

Chromosomes are found in ________ in all animals.

Answer 3

pairs

Question 4

Locus (singular)/loci (plural) is a site of a particular region/gene on a __________.

Answer 4

Chromosome

Question 5

An allele is:

Answer 5

an alternative form of a gene.

Question 6

Epistasis is:

Answer 6

How one gene is affecting the expression of another gene.

Question 7

What are the five types of gene action/dominance?

Answer 7

• Partial dominance
• Codominance
• Complete dominance
• Overdominance
• No dominance

Question 8

How is genetic information transferred?

Answer 8

DNA

Question 9

_______________ pieces of DNA carry the same genes.

Answer 9

Homologous

Question 10

A(n) ____________ is an alternative form of a gene.

Answer 10

allele

Question 11

___________ genes ARE functionally the same, while ________________ genes ARE NOT functionally the same.

Answer 11

Homozygous ; heterozygous

Question 12

True of False. A genome is most of the genes in a cell or organism.

Answer 12

False! A genome consists of ALL genes in a cell or organism.

Question 13

A ___________ allele has an effect on the phenotype when it is homozygous AND heterozygous.

Answer 13

dominant

Question 14

A ____________ allele has an effect on phenotype ONLY when it is homozygous.

Answer 14

recessive

Question 15

Additive effect is:

Answer 15

the combined effects of genetic alleles at two or more gene loci are equal to the sum of their individual effects.

Question 16

For complete dominance, what two genotypes have the same phenotype?

AA
aa
Aa

Answer 16

AA and Aa

Question 17

True or False. Incomplete dominance has a heterozygous genotype (Aa) express a phenotype in between the homozygous genotypes (AA and aa), except it is NOT exactly midway.

Answer 17

True!

Question 18

No dominance has the heterozygous genotype’s (Aa) phenotype exactly in between the homozygous genotypes (AA and Aa) or partially toward one end?

Answer 18

Exactly in between

Question 19

What is the difference between No Dominance and Partial Dominance?

Answer 19

For heterozygous genotypes, No Dominance phenotypes lay exactly in between the homozygous genotypes.

Partial dominance lays toward one end or the other. NOT exactly in the middle.

Question 20

In Codominance, how many phenotypes will there be with a simple genotype

(example: AA, Aa, aa)

Answer 20

3

Question 21

In Overdominance, where does the heterozygous genotype’s expression land in comparison to the homozygous genotypes?

Answer 21

HIGHER than the average of both homozygous genotypes.

Question 22

Define gene interaction:

Answer 22

The interactions between two or more genes result in a phenotype that differs from the phenotype expected if the genes were independent of each other.

Question 23

Define epistasis in your own words.

Answer 23

When the expression of one gene affects the expression of another on another loci.

Question 24

What does G, in P = G + E, expand into? And what do each letter stand for?

Answer 24

G = D + I + A

D = dominance

I = epistasis

A = additive effect

Question 25

What are two types of gene-trait relationships that we mentioned in class?

Answer 25

Pleiotropy and Lethal Genotypes

Question 26

What is the difference between epistasis and pleiotropy?

Answer 26

Epistasis is one gene expression affecting another gene expression (of the same trait).

Pleiotropy is one single gene affecting multiple traits.

Question 27

Define genomic imprinting.

Answer 27

The ability of a gene to be expressed depends on the sex of the parent that the gene is coming from.

Question 28

What are the three kinds of sex-related inheritance?

What is an example of each?

Answer 28

Sex-linked - Color blindness in males only
Sex-limited - milk and egg production in females only
Sex-influenced - Scurs are more frequent in males

Question 29

What is an example of a non-additive effect?

Answer 29

Any form of dominance.