past paper questions paper 2

Question 1

what is a gene pool? (1) 2017

Answer 1

All the alleles of all genes in a population at one time

Question 2

Lord Howe Island in the Tasman Sea possesses two species of palm tree which have arisen via sympatric speciation. The two species diverged from each other after the island was formed 6.5 million years ago. The flowering times of the two species are different . Using this information , suggest how these two species of palm tree arose by sympatric speciation . (5) 2017

Answer 2

• Occurs in the same population
• Mutations cause different flowering times
• No gene flow
• Change in allele frequency
• Disruptive natural selection
• Eventually different species formed and cannot interbreed to produce fertile offspring

Question 3

What is meant by the term phenotype? (2) 2017

Answer 3

The gene expressed and its interaction with the environment

Question 4

Describe how alterations to tumour suppressor genes can lead to the development of tumours. (3) 2018

Answer 4

• Increased methylation of tumour suppressor genes
• Mutation in tumour suppressor genes
• Amino acid sequence is altered
• Results in uncontrollable cell division

Question 5

In genetic crosses , the observed phenotypic ratios obtained in the offspring are often not the same as the expected ratios . Suggest two reasons why (2) 2018

Answer 5

1) small sample size
2) fertilisation and fusion of gametes is random

Question 6

what is meant by a genome ? (1) 2018

Answer 6

All the dna in an organism

Question 7

Males have sex chromosomes XU and females have XX. R = red eyes and r = white eyes. Male fruit flies are more likely than females to have white eyes explain why. (2) 2021

Answer 7

• Females would need 2 recessive alleles.
• Males only have one X chromosome therefore only need one copy of a recessive allele