TOPIC 3 - INHERITANCE

Question 1

Describe the process of DNA replication (4)

Answer 1

1. helicase unwinds DNA double helix breaking H bonds
2. 2 template strands formed
3. free nucleotides attach to template strands
4. DNA polymerase joins nucleotides forming phosphodiester bonds
5. new DNA contains half the original DNA

Question 2

how does Rhythmical tapping of the chest wall ease CF symptoms (2)

Answer 2

• loosens mucus
• mucus can be expelled more easily
• airways become clearer

Question 3

Explain why people with cystic fibrosis can have breathing difficulties.

Answer 3

• Thicker mucus is produced
• cilia unable to waft mucus out of lungs
• loss of SA of airways
• reduced gaseous exchange
• ucus can trap bacteria causing respiritory infections

Question 4

define gene

Answer 4

a specific sequence of DNA bases which codes for a particular protein

Question 5

what is an autosome?

Answer 5

any chromosome that isnt a sex chromosome

Question 6

what are linked genes

Answer 6

• do not idependantly assort in meiosis
• passed on to offspeing together

Question 7

what is sex linkage?

Answer 7

• inheritance of a gene is dependant on sex
• males more likely to develop condition as they only have one x chromosome

Question 8

what 3 mechanisms increase genetic diversity of gametes?

Answer 8

independant assortment + crossing over + random fertilisation

Question 9

what is independant assortment?

Answer 9

production of different combinations of alleles in daughter cells due to the random alignment of homologous pairs along the equator of the spindle during meiosis I

Question 10

describe crossing over

Answer 10

• non sister chromatids cross over
• at chiasmata
• section of chromosome breaks off and joins with other chromosome