Genetic diversity and adaptation

Question 1

How does a change in base sequence of DNA effect a protein?

Answer 1

• change in base sequence of DNA
• change in base sequence of mRNA
• change in amino acid sequence
• change in ionic/hydrogen/disulphide bonds
• change in tertiary structure of protein
• change in protein function

Question 2

What does ‘fitness’ mean?

Answer 2

organisms with advantageous alleles to pass on to offspring

Question 3

What is the pneumonic for natural selection?

Answer 3

Very - variation
Massive - mutation
Elephants - environment
Cause - compete
Sandstorms - survive
Round - reproduce
Africa - advantageous alleles

Question 4

What are the stages of natural selection?

Answer 4

• there is genetic diversity within any population due to mutations in the gene pool. These mutations can result in new alleles of genes
• this allele may be harmful or beneficial dependent on the environment eg. there may be environmental change which changes conditions and gives the individual that possess new alleles an advantage
• some individuals can better survive their competition due to alleles, and will survive and reproduce
• the advantageous alleles are passed onto the next generation and new offspring have ‘advantageous alleles’ and will survive to breed
• this continues over time and adaptations may be anatomical, physiological or behavioural

Question 5

What is selection?

Answer 5

the process by which organisms that are better adapted to the environment survive and breed, while those who are less well adapted tend not to

Question 6

What is the difference between directional selection and stabilising selection?

Answer 6

directional selection changes the characteristics of a population, whereas stabilising selection preserves them

Question 7

What is a selection pressure?

Answer 7

something that puts the population at risk eg. antibiotics in a bacteria culture

Question 8

What is directional selection and give an example?

Answer 8

individuals that have varied alleles are favoured, so the mean will move in the direction of these individuals

eg. antibiotic resistance

• a mutation occurred in the allele of a gene in a bacterium that allowed it to produce an enzyme which broke down antibiotics before they could kill bacteria
• this gave the bacteria an advantage, so was able to survive whilst the other bacteria were killed
• bacteria with advantageous alleles divides by binary fission and so a population of antibiotic resistant bacteria build up
• the distribution curve shifts in the direction of a population having greater antibiotic resistance (mean, mode,median remain the same just shifted)

Question 9

What is stabilising selection and give an example?

Answer 9

• when environmental conditions remain stable, individuals with phenotypes closest to the mean are favoured an more likely to pass on alleles - it therefore tends to eliminate the extreme phenotypes

eg. human birth rate

• mortality rate is greatest at the 2 extremes - very light and very heavy
• very small babies have a high SA:V ratio so lose heat quickly, very big babies will be difficult to birth
• those around the mean are less likely to die and so populations characteristics are preserved rather than changed
• mean becomes more frequent

Question 10

What are the 3 types of adaptation as a result of natural selection?

Answer 10

• anatomical eg. shorter ears and thicker fur
• physiological eg. oxidising of fat rather than carbs produces additional water in a hot environment
• behavioural eg. migration

Question 11

What is the difference between a gene and an allele?

Answer 11

A gene is a portion of DNA that determines a certain trait. An allele is a specific form of a gene. Genes are responsible for the expression of traits. Alleles are responsible for the variations in which a given trait can be expressed