Inheritance, selection and speciation

Question 1

What is a gene?

Answer 1

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

Question 2

What is an allele?

Answer 2

Different version of the same gene

Question 3

What is meant by genotype?

Answer 3

The genetic composition of an organism

Question 4

What is meant by phenotype?

Answer 4

The expression of genotype in an organism and it’s interaction with the environment

Question 5

What is meant by a dominant allele?

Answer 5

It is always expressed in the phenotype of an organism

Question 6

What is meant by a recessive allele?

Answer 6

An alleles whose characteristic will only appear in the phenotype if two copies are present- homozygous recessive

Question 7

What are co-dominant alleles?

Answer 7

Alleles that are both expressed in the phenotype and neither one is recessive

Question 8

What is meant by homozygous?

Answer 8

Two copies of the same allele , either dominant or recessive

Question 9

What is meant by heterozygous?

Answer 9

When an organism carries two different alleles, usually one dominant and one recessive and can often be described as a “carrier”

Question 10

What are gametes?

Answer 10

Sex cells i.e. egg and sperm. They only contain one allele for each gene

Question 11

What is monohybrid inheritance?

Answer 11

The inheritance of a single characteristic/gene controlled by different alleles

Question 12

What sex chromosomes do female mammals have?

Answer 12

XX

Question 13

What sex chromosomes do male mammals have?

Answer 13

XY

Question 14

How many pairs of chromosomes do humans have?

Answer 14

23

Question 15

What is the name given to genes/ alleles found on either the X or Y chromosome?

Answer 15

Sex linked

Question 16

What is meant by a species?

Answer 16

A group of similar organisms that can breed together to produce fertile offspring

Question 17

What is meant by the gene pool?

Answer 17

The range of alleles present within a population of a species

Question 18

What is meant by allele frequency?

Answer 18

How often an allele occurs in a population

Question 19

What are the equations of the Hardy Weinburg equations?

Answer 19

p² + 2pq + q² = 1

P + q = 1

Question 20

What can the Hardy Weinburg equations

Answer 20

Allele and genotype frequency , percentage of population with a certain genotype

Question 21

What does each part of the Hardy Weinburg principle mean?

Answer 21

P = frequency of dominant allele
Q = frequency of recessive allele
2PQ = frequency of heterozygous genotype 
p² = frequency of homozygous dominant genotype 
q² = frequency of homozygous recessive genotype

Question 22

What does the Hardy Weinburg principal predict?

Answer 22

The proportion of dominant and recessive alleles of any gene in a population remains the same from one generation to the next, provided certain conditions are met

Question 23

What conditions does the Hardy Weinburg equations need to meet?

Answer 23

• No mutations
• population is isolated
• no selection of any sort
• population is large
• random mating occurs

Question 24

What is meant by selection?

Answer 24

Process that results in the best-adapted organisms in a population to survive, breed and pass on their favourable alleles to the next generation

Question 25

What is a selection pressure?

Answer 25

The environmental force altering the frequency of alleles in a populations gene pool

Question 26

What is a major cause in changes of allele frequencies in a population?

Answer 26

Gene mutations

Question 27

What are the different types of selection?

Answer 27

Natural , stabilising and directional

Question 28

What is stabilising selection?

Answer 28

The individuals with alleles for characteristics towards the middle of the range are more like to breed and produce ( peak part of a graph)

Question 29

What is directional selection?

Answer 29

Individuals with alleles for characteristics of an extreme phenotype are more likely to survive and reproduce, can be in response to an environmental change ( graph shifts to left or right)

Question 30

When does stabilising selection occur?

Answer 30

When environmental conditions remain constant

Question 31

What is speciation and when does it occur?

Answer 31

Formation of new species from an existing species, occurs when populations of the same species become isolated in some way I.e. Reproductively or geographically