Inheritance And Selection

Question 1

What is a genotype?

Answer 1

The genetic composition of an organism

All alleles in an organism

Question 2

What is a phenotype?

Answer 2

The characteristics of an organism, often visible, resulting from its genotype and the environment

Question 3

What is a gene?

Answer 3

A section of DNA that is a sequence of nucleotides that determine a singular characteristic
Codes for a specific amino acid

Question 4

What is an allele?

Answer 4

One of the different forms of a gene

Question 5

What is a dominant allele?

Answer 5

An allele that is always expressed in the phenotype

Question 6

What is a recessive allele?

Answer 6

When the allele is only expressed if it is homozygous or diploid as it is masked by the dominant

Question 7

What are co-dominant alleles?

Answer 7

When two alleles are equally dominant and do contribute to the phenotype

Question 8

What is monohybrid inheritance?

Answer 8

The inheritance of a single gene

Question 9

What are the sex chromosomes for male and female?

Answer 9

Male - XY

Female - XX

Question 10

How are sex linked diseases inherited?

Answer 10

For most of the X chromosome there is no equivalent portion of the Y chromosome
Recessive alleles on the non-homologous portion of the X chromosome will appear more frequently in males
Because there is not dominant allele to stop the recessive allele being expressed

Question 11

In sex linked diseases who is the disease inherited from?

Answer 11

A male inherits it from his mother as his father will have a Y chromosome and so cannot pas an allele on
But a father can pass it to a daughter on the X chromosome

Question 12

What are the blood groups and which ones are recessive or dominant?

Answer 12

A - AA or AO
B - BB or BO
AB - AB
O - OO

A and B are co dominant and O is recessive

Question 13

What five conditions are assumed when calculating Hardy-Weinberg?

Answer 13

No mutations
An isolated population
Mating is random
No selection 
The population is large

Question 14

What does the Hardy-Weinberg principle predict?

Answer 14

That the proportion of dominant and recessive alleles of any gene in a population remains the same from one generation to the next

Question 15

What is directional selection?

Answer 15

If the environmental conditions change so that those with phenotype a further away from the mean are more adapted for the new conditions

Question 16

What is stabilising selection?

Answer 16

When environmental conditions stay stable so individuals with phenotypes closer to the mean are favoured

Question 17

What is speciation?

Answer 17

The evolution of a new species from existing species

Question 18

Stages of geographical isolation

Answer 18

When a physical barrier prevents two populations from breeding
Climate change creates two different conditions, one hot, one cold
Those with advantageous phenotypes survive and breed passing on the allele for it
Others not adapted die
Allele type and frequency in the gene pools become more different until they are different species
They will not be able to breed to produce fertile offspring