IPM

Question 1

How can mutations lead to human evolution?

Answer 1

Most mutations (permanent changes in nucleotide sequences of DNA) do not affect the phenotype.

But if a mutation creates a new phenotype that is better adapted to environmental changes (than the rest of the population), the mutation is likely to spread throughout the population over a small number of generations.

For example, over time the size of the human brain has increased, as those born with a bigger brain were found to be at a survival advantage.

Question 2

Variation

Answer 2

Many different combinations of an allele.

This means that the genetic variation is high.

Question 3

How can new alleles be created?

Answer 3

Only by mutations

Question 4

Mutations

Answer 4

permanent changes in nucleotide sequences of DNA which rarely affect the phenotype.

Question 5

Phenotype

Answer 5

Set of observable characteristics of an individual

Question 6

DNA extraction experiment?

Answer 6

Grind a small sample of fruit in soapy water
Filter the sample to produce a filtrate
Very slowly pour ice-cold ethanol into the filtrate
DNA moves into the ethanol by precipitation and can then be removed by a wire loop.

Question 7

Describe the structure of DNA (4 marks)

Answer 7

DNA is a polymer consisting of two long strands of small units that repeat throughout the structure, called nucleotides.

A nucleotide is made up of a phosphate and a base attached to the sugar.

The sugar and phosphates of nucleotides from the long strands.

Weak hydrogen bonds between opposite bases hold the two strands together.

Question 8

Desrcribe meiosis

Answer 8

Prophase 1 - homologous sections of homologous pairs cross over.

Anaphase 1 - sister chromatids stay together and the homologous pairs get pulled apart.

telephose 1 - fully split apart and are at opposite ends and begin to unravel at its chromatid state.

Produces four genetically different daughter cells.