Inheritance

Question 1

Gene

Answer 1

A sequence of bases on a DNA molecule that codes for a protein which results in a characteristic

Question 2

Allele

Answer 2

A version of a gene. Most plants and animals have two alleles of the same gene, one from each parent.

Question 3

Genotype

Answer 3

The alleles an organism has

Question 4

Phenotype

Answer 4

The characteristics an allele produces

Question 5

Codominant

Answer 5

Alleles that are both expressed in a phenotype

Question 6

Locus

Answer 6

The fixed position of a gene on a chromosome.

Question 7

Homozygote

Answer 7

An organism that carries two copies of the same allele

Question 8

Heterozygote

Answer 8

An organism that carries both alleles

Question 9

What is monogenic inheritance?

Answer 9

The inheritance of a characteristic controlled by a single gene

Question 10

What is dihybrid inheritance?

Answer 10

Involving genes of two loci

Question 11

What is a sex-linked characteristic?

Answer 11

When the allele that codes for the characteristic is located on a sex chromosome. Most genes that are carried on sex chromosomes are on the x chromosome, these are called X-linked genes.

Question 12

Why is it more likely for males to show recessive phenotypes for sex-linked genes?

Answer 12

Males only have one X chromosome, if there is a recessive allele on this chromosome, such as a faulty one to cause an X-linked disorder, this characteristic will show. If a female has a faulty recessive allele on one chromosome, she will probably have a functioning allele of the same gene on the other chromosome.

Question 13

What is autosomal linkage?

Answer 13

Gene loci present on the same autosome (non sex chromosome) that are often inherited together. The closer together two genes are on the autosome, the more linked they are because it becomes less likely that they will be split up during crossing over in prophase 1 of meiosis.

Question 14

What is an epistatic gene?

Answer 14

A gene that masks the expression of another gene. Different genes at different loci on different chromosomes can interact to affect one phenotypic characteristic.

Question 15

How to predict the phenotypic ratio for a recessive epistatic allele

Answer 15

Having two copies of the recessive epistatic allele blocks the expression of another gene.
If you cross a homozygous recessive parent with a homozygous dominant parent you will get a 9:3:4 phenotypic ratio

Question 16

How to predict the phenotypic ratio for a dominant epistatic allele

Answer 16

Having at least one copy of the dominant epistatic allele masks the expression of the other gene. Crossing a homozygous recessive parent with a homozygous dominant parent produces a 12:3:1 phenotypic ratio.