DNA & inheritance

Question 1

What is a gene

Answer 1

section of DNA that contains a specific sequence of bases which code for a specific protein

• length of DNA determines single characteristic of an organism
• unit of inheritance

Question 2

Mutation

Answer 2

sudden change in DNA of an organism

Question 3

Gene mutation

Answer 3

change in structure of a gene

Question 4

Chromosome mutation

Answer 4

change in number / structure of chromosome

Question 5

Sickle cell anaemia

Answer 5

gene that codes haemoglobin undergoes mutation to produce abnormal haemoglobin
- less soluble
- tends to stick together
- distort RBC ; sickle-shaped ( half moon )
- cannot transport oxygen
- may block small capillaries ; larger diameter
- destruction of sickle cells causes severe form of anemia

Question 6

Albinism

Answer 6

body can no longer produce melanin pigment
- white hair
- very light-coloured skin
- pink eyes

Question 7

Down’s Syndrome

Answer 7

• 24 chromosomes instead of 23 in ovum
• child will have 47 chromosomes instead of 46
• slow physical & mental development
• broad flat face
• shorter life span
• extra chromosome in 21st group ; 3 instead of 2

Question 8

Mutagens

Answer 8

agents increasing mutation rate
- change structure of gene ; altering the way it works

Question 9

Examples of mutagens

Answer 9

• chemicals : mustard gas & tar from cigarette smoke
• high energy radiation : X-rays & UV light

Question 10

Significance of mutations

Answer 10

main source of genetic variation ; new alleles of genes produced

Question 11

Other causes of variation

Answer 11

• meiosis
• random mating between organisms
• random fertilisation of gametes