Topic 3B - Reproduction and Inheritance

Question 1

EQ. State what is meant by the term sex-linkage. (2 marks)

Answer 1

• when the allele that determines the trait is only found on the sex chromosome
• expression of traits is determined by gender

Question 2

EQ. Explain what is meant by an inherited recessive disorder. (2 marks)

Answer 2

• its caused by a faulty gene

- only expresed if genotype is homozygous recessive

Question 3

EQ. Give one advantage and disadvantage of adult screening. (2 marks)

Answer 3

• identifies risk of developing disease in future so choices can be made
• the result may affect life insurance

Question 4

EQ. Give one advantage and disadvantage of Preimplantation Genetic Diagnosis. (2 marks)

Answer 4

• only healthy embryos are implanted so they do not need to make a decision about abortion
• PGD involves IVF which can be emotionally traumatising and only has a success rate of 30%

Question 5

EQ. Give one advantage and disadvantage of Amniocentesis. (2 marks)

Answer 5

• gives choice to abort child

- carry risk of miscarriage

Question 6

EQ. Suggest how a change in the mid region of the sperm may make it non-motile (2 marks)

Answer 6

• if it made the mitochondria less efficient

- ATP production could be inhibited reducing movement in the flagellum

Question 7

EQ. State 3 assumptions we have to make to use the Hardy-Weinburg theory. (3 marks)

Answer 7

• No mutations, migration or emigration
• No selective pressure for or against a specific genotype
• Population size is infinite

Question 8

EQ. Describe the 3 types of adaptations and an example for each. (3 marks)

Answer 8

• behavioural is the way an organism acts e.g scorpions dance to increase the chance to successful mating
• physiological is the chemical processes e.g brown bears hibernate by slowing their metabolism
• anatomical is the structural features e.g otters have a streamline shape so they can swim faster in water

Question 9

Define a locus

Answer 9

the location of a gene on a chromosome