3.7 Genetics, population and ecosystems

Question 1

Define genotype

Answer 1

The genetic constitution of an organism (the alleles it has for a gene)

Question 2

Define phenotype

Answer 2

expression of the genes and its interaction with the environment

Question 3

What is a homozygous chromosome?

Answer 3

a pair of homologous chromosomes carrying the same alleles for a single gene

Question 4

What is a heterozygous chromosome?

Answer 4

a pair of homologous chromosomes carrying two different alleles for a single gene

Question 5

What is a recessive allele?

Answer 5

an allele only expressed if no dominant allele is present

Question 6

What is a dominant allele?

Answer 6

an allele that will always be expressed in the phenotype

Question 7

What is a codominant allele?

Answer 7

When both alleles are equally dominant and expressed in the phenotype

Question 8

What is a sex linkage?

Answer 8

A gene whose locus is on the X chromosome

Question 9

What is the autosomal linkage?

Answer 9

Genes that are located on the same chromosome (not on the sex chromosomes)

Question 10

What is epistasis?

Answer 10

When one gene modifies or masks the expression of a different gene at a different locus.

Question 11

What is a monohybrid cross?

Answer 11

A genetic inheritance cross of a characteristic determined by one gene

Question 12

What is a dihybrid cross?

Answer 12

A genetic inheritance cross for a characteristic determined by two genes at the same times

Question 13

What happens in a genetic cross?

Answer 13

you must show parental phenotype and genotype, the possible gametes, the offspring genotype and phenotype and the proportion of each phenotype.

Question 14

What happens in a dihybrid cross?

Answer 14

Figure out F1 and then cross F1 offspring together
•Each possible gamete should have one copy of each gene
•When homozygous dominant is crossed with homozygous recessive the offspring will be heterozygous
•Ratio of each phenotype is 9:3:3:1

Question 15

When is the ratio of a dihybrid cross not 9:3:3:1?

Answer 15

There is autosomal linkage or crossing over in meiosis

Question 16

How does crossing over in meiosis affect a dihybrid cross?

Answer 16

New combinations of alleles in the gametes, means the predicted gametes in the punnet square may differ

Question 17

How does autosomal linkage affect a dihybrid cross

Answer 17

Alleles for each gene linked on the same chromosome will be inherited together.

Question 18

What is a Hardy- Weinberg principle?

Answer 18

This is a mathematical model which can be used to predict the allele frequencies within a population.

Question 19

What is a gene pool?

Answer 19

All the alleles of all the genes within a population at one time

Question 20

What is a population?

Answer 20

All the individuals of one species in one area at one time

Question 21

What is an allele frequency?

Answer 21

The proportion of an allele within the gene pool

Question 22

What is the equation for Hardy Weinberg principle?

Answer 22

p2 + 2pq + q2 = 1 or p + q =1

Question 23

What is the ‘p’ in the Hardy Weinberg principle?

Answer 23

The frequency of the dominant allele

Question 24

What is the q in the Hardy Weinberg principle?

Answer 24

The frequency of the recessive allele

Question 25

What is the ‘p2’ in the Hardy Weinberg principle?

Answer 25

The frequency of the homozygous dominant genotype

Question 26

What is the ‘2pq’ in the Hardy Weinberg principle?

Answer 26

The frequency of the heterozygous genotype

Question 27

What is the ‘q2’ in the Hardy Weinberg principle?

Answer 27

The frequency of the heterozygous genotype

Question 28

What is variation?

Answer 28

The individuals within a population of a species may show a wide range of variation is phenotype that is due to genetic and environmental factors

Question 29

What is the primary source of genetic variation?

Answer 29

Mutation