Genetics

Question 1

Chargaff’s rule

Answer 1

Adenine pairs with Thymine

Guanine pairs with Cytosine

The bases form weak hydrogen bonds

Question 2

Mitosis

Answer 2

The process of cell division in which the exact duplication of chromosomes in the parent cells then splits producing daughter cells that are genetically identical to parent cells

Question 3

Functions of mitosis

Answer 3

Cell growth

Replace worn out cells

Repair damaged cells

Question 4

Stages of mitosis

Answer 4

DNA condenses into chromosomes and each chromosome replicates so it contains two identical chromosomes

The chromosomes align in the middle of the parent cell

Spindle fibres attached the centromere and contract pulling away

The cell splits in two to produce two genetically identical diploid daughter cells

Question 5

Meiosis

Answer 5

A form of cell division which is called reduction division (one diploid cell producing four genetically different haploid daughter cells) that only takes place in the sex organs

Question 6

Function of meiosis

Answer 6

To produce gametes with half the number of chromosomes of all the other non-gamete cells in the body

Question 7

Stages of meiosis

Answer 7

Before meiosis begins, all the chromosomes duplicate to form two chromatids

Homologous pairs of chromosomes randomly align in the middle of the parent cells

Spindle fibres attach to the centromere and contract pulling chromosomes to opposite poles

Each cell divides again so each new cell only contains one chromatids from each chromosome

Four different haploid daughter cells are produced

Question 8

Genetic variation is caused by

Answer 8

Genetics and environment

Question 9

Haemophilia

Answer 9

Causes a problem with the blood-clotting mechanism. Sufferers are at risk for excessive bleeding. Caused by a recessive allele on the X chromosome

Question 10

Cystic fibrosis

Answer 10

Sufferers have frequent and serious lung infections and problems with food digestion. Caused by a recessive allele so affected individuals must be homozygous recessive

Question 11

Huntington’s disease

Answer 11

Affects nerve cells in the brain leading to brain damage. Only becomes apparent in middle age, is fatal and has no cure. It’s caused by the presence of a dominant allele

Question 12

Down’s syndrome

Answer 12

Caused by an extra of chromosome, causes an issue in muscle tone and cognitive development

Question 13

Amniocentesis

Answer 13

Involves inserting a needle into the amniotic fluid surrounding a foetus and examining the fluid for genetic abnormalities. May cause a miscarriage