Unit 1 slowly building up

Question 1

What is a somatic cell

Answer 1

Any cell in the body other than cells that are involved in reproduction and the stem cells that divide to make them.
They divide by mitosis to make more somatic cells (diploid)

Question 2

What is a germline cell

Answer 2

Gametes (sperm & ova and the stem cells that divide to make them).
They divide by mitosis AND meiosis (Haploid)

Question 3

How many PAIRS of chromosomes does a diploid cell have

Answer 3

23

Question 4

What happens when a germline cell divides by meiosis

Answer 4

It undergoes 2 divisions:
Firstly separating homologous chromosomes.
Secondly separating chromatids.
4 daughter cells are produced that are all haploid.

Question 5

What is differentiation

Answer 5

When an unspecialised cell changes into a specialised cell.
The cell expresses certain genes to produce proteins characteristic for that type of cell

Question 6

What type of stem cells are multipotent

Answer 6

Tissue stem cells as they can only differentiate into the types of cell found in a particular tissue
E.G blood stem cells can only change into white blood cells (phagocytes, lymphocytes) or red blood cells, platelets

Question 7

What type of stem cells are pluripotent

Answer 7

Embryonic stem cells as all the genes in embryonic stem cells can be switched on so they can differentiate into any type of cell

Question 8

What are therapeutic uses of stem cells

Answer 8

Stem cells are involved in growth and repair of damaged organs and tissues not cells
E.G corneal repair in the eye, regeneration of damaged skin

Question 9

What is the structure of a DNA nucleotide

Answer 9

deoxyribose sugar, phosphate, base

Question 10

What is the structure of DNA

Answer 10

DNA consists of 2 strands of nucleotides twisted into a double helix

Question 11

How are 2 DNA strands held together

Answer 11

They are held together by hydrogen bonds

Question 12

What does DNA replication require

Answer 12

A DNA template
Free DNA nucleotides
DNA polymerase
Primers
ATP

Question 13

What must happen before cell division

Answer 13

DNA replication so that every daughter cell will inherit an identical copy of the DNA

Question 14

What are the steps of PCR

Answer 14

DNA is heated to between 92 and 98°C to separate the strands.
It is then cooled to between 50 and 65°C to allow primers to bind to target sequences.
It is then heated to between 70 and 80°C for heat-tolerant DNA polymerase to replicate the region of DNA.

Question 15

What is Polymerase Chain Reaction (PCR)

Answer 15

PCR amplifies DNA using complementary primers for specific target sequences

Question 16

What are the requirements for PCR

Answer 16

DNA sample
Primers
Heat tolerant DNA polymerase
Free nucleotides

Question 17

What is the first stage of replication

Answer 17

DNA is unwound, weak hydrogen bonds break between base pairs and form two template strands.
DNA template strands become stabalised and expose their bases at a Y-shaped replication fork

Question 18

What is the second stage in DNA replication

Answer 18

The leading strand is synthesised continuously in a 5’ to 3’ direction. A primer is needed to start replication
The lagging strand is synthesised in fragments because DNA polymerase can only add DNA nucleotides in a 5’ to 3’ direction.

Question 19

What is stage three in DNA replication

Answer 19

The fragments are then sealed together by ligase.
The 2 new strands twist to form double helixes. Each is identical to the original strand.