inheritance

Question 1

Define gene:

Answer 1

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

Question 2

Define allele:

Answer 2

Different versions of the same gene

Question 3

Define diploid:

Answer 3

2 copies of each chromosomes

Question 4

Define locus:

Answer 4

The fixed position of a gene on each chromosome

Question 5

Define genotype:

Answer 5

All of the alleles an organism carries on its chromosomes

Question 6

Define phenotype:

Answer 6

Observable characteristics of an organism, which results from the genotype and environmental factors.

Question 7

Define dominant:

Answer 7

Always expressed in the phenotype

Question 8

Define recessive:

Answer 8

Only expressed in the phenotype if homozygous

Question 9

Define co-dominant:

Answer 9

Both alleles expressed as neither is recessive

Question 10

Define homozygous:

Answer 10

2 copies of the same allele

Question 11

Define heterozygous:

Answer 11

2 different alleles

Question 12

What does F1 mean?

Answer 12

The first set of offspring

Question 13

What can genetic diagrams be used for?

Answer 13

To predict the genotypes and phenotypes of the offspring produced if two parents are crossed

Question 14

What is monohybrid inheritance?

Answer 14

Inheritance of a characteristic controlled by a single gene

Question 15

What do monohybrid crosses show?

Answer 15

The likelihood of different alleles of that gene (and the characteristic) being inherited by offspring of certain parents

Question 16

Define phenotypic ratio:

Answer 16

The ratio of different phenotypes in the offspring

Question 17

What is the phenotypic ratio when crossing two heterozygous parents in a monohybrid cross?

Answer 17

3:1 ratio of dominant: recessive

Question 18

Define multiple alleles:

Answer 18

More than two alleles of the same gene

Question 19

What is dihybrid inheritance?

Answer 19

Inheritance of two characteristics which are controlled by different genes

Question 20

What do dihybrid crosses show?

Answer 20

The likelihood of offspring inheriting certain combinations of the two characteristics from particular parents

Question 21

What is the phenotypic ratio when crossing two parents (heterozygous for both alleles) in a dihybrid cross?

Answer 21

9:3:3:1

Question 22

What does it mean that some characteristics are sex linked?

Answer 22

Alleles that code for them are located on sex chromosomes

Question 23

What does the fact that males only have one X chromosome mean?

Answer 23

Males often only have one allele for sex linked genes, so will express characteristic of this allele even if its recessive- males are more likely to show recessive phenotypes for sex linked genes

Question 24

Describe autosomal linkage:

Answer 24

Genes on the same autosome are linked, so will stay together during independent segregation in meiosis 1. Therefore they will be passed on to the offspring together

Question 25

Why would autosomal linked genes be split up?

Answer 25

Crossing over would split them up first. The closer together chromosomes are, the more closely linked they are, so the less likely they are to be split by crossing over.

Question 26

What is epistasis?

Answer 26

When the allele of one gene masks the expression of other genes

Question 27

What is the phenotypic ratio for a recessive epistatic allele?

Answer 27

When two homozygous parents are crossed (resulting in heterozygous offspring) the F2 generation will be a 9:3:4 ratio of dominant both: dominant epistatic recessive other: recessive epistatic

Question 28

What is the phenotypic ratio for a dominant epistatic allele?

Answer 28

When two homozygous parents are crossed (resulting in heterozygous offspring) the F2 generation will be a 12:3:1 ratio of dominant epistatic: recessive epistatic: dominant other: recessive both