Inheritence/ variation 3

Question 1

How do gene mutations cause variation

Answer 1

-the dna base sequence is altered which then results in a new polypeptide

Question 2

How does crossing over result in variation?

Answer 2

• The chromosomes cross over where the alleles are crossed and new combinations of alleles are formed

Question 3

How does independent segregation cause variation?

Answer 3

• during meiosis II
  -the fist separation of homologous chromosomes happens separately from the separation of the other pair , resulting in random allele combinations

Question 4

How does random fertilisation cause variation?

Answer 4

-ocurrs during sexual reproduction,

Question 5

What are characteristic influenced by genetic factors

Answer 5

-controlled by one or two genes
-expressed as phenotypes
-represented as distinct groups on a bar chart.

Question 6

What are characteristic by environmental factors

Answer 6

• controlled by many genees
  -have no separate categories
  -normal distribution curve

Question 7

What are the 3 selection pressures in natural selection

Answer 7

predation
disease
competition

Question 8

What is stabilising selection

Answer 8

-when the environment isn’t changing
-the average in the graph is the one passing the genes as they’re not advantageous for a specific allele.

Question 9

What’s directional selection?

Answer 9

-when the environment is changing
-the change in environment selects for those organisms with allies for a phenotype towards an extreme range

Question 10

What’s disruptive selection

Answer 10

-opposite of stabling selection
-involves selection of phenotype from extreme
-most important bringing about evolutionary change
-the average isn’t advantaous

Question 11

When does evolution occur

Answer 11

When there’s a change in allele frequencies in a population

Question 12

What’s speciation

Answer 12

• evolution of new species from existing ones

Question 13

What can reproductive isolation of 2 populations cause in a gene pool?

Answer 13

• decreased variation
  -accumilation of difference

Question 14

How do new species arise from reproductive isolation

Answer 14

• allopatric speciation
  -they arrive from existing species

Question 15

describe allopatric speciation

Answer 15

-population already has variation due to meiosis, mutations and graphological differences
-populatons are isolated meaning there’s no gene flow
-different selection pressures for different phenotypes
-frequency of selected phenotypes
-

Question 16

why might allelic frequencies change. ( number of alleles for specific gene )

Answer 16

-mutations may occur independently in each population