Gene Expression

Question 1

Cells which can mature into any type of body cell

Answer 1

Totipotent (or omnipotent)

Question 2

Cells which can differentiate into almost all types of cells eg in a blastocyst

Answer 2

Pluripotent

Question 3

Cells which can differentiate into a related family of cells eg blood or muscle cells. Used by body to repair and replace damaged tissue

Answer 3

Multipotent

Question 4

normal, specialised adult cells that have been genetically reprogrammed to become undifferentiated, pluripotent stem cells. iPSCs are a new development, still at the research stage, but they may solve some of the problems of both adult and embryo stem cells.

Answer 4

Induced pluripotent stem cells

(iPSCs)

Question 5

Explant

Answer 5

Small samples of plant used for tissue culture/micro-propagation.

Question 6

Callus

Answer 6

A mass of undifferentiated plant cells grown from individual cells from a plant. A callus can be stimulated to form a plantlet

Question 7

PGRs

Answer 7

Plant Growth Regulators- added to callus to allow them to grow into plantlets for propagation

Question 8

Multipotent cells still existing in adult animals. Difficult to find and culture as usually only multipotent

Answer 8

Adult stem cells

Question 9

Embryonic stem cells

Answer 9

Pluripotent cells existing in embryos ie before they have differentiated. From ‘spare’ IVF (In vitro fertilisation) embryos- therefore ethically debatable

Question 10

Transcriptional factors

Answer 10

Specific molecules which move from cytoplasm to nucleus to stimulate transcription

Question 11

Small interfering RNA- small double-stranded sections of RNA which prevent gene expression by bonding to complementary base pairs to ‘block’ transcription

Answer 11

siRNA

Question 12

Heritable changes in gene function without changing the base sequence of DNA, caused by changes in the environment

Answer 12

Epigenetics

Question 13

Methyl groups are added to the DNA which represses transcription as it leads to the DNA becoming more tightly packed.

Answer 13

Methylation

Question 14

Acetylation

Answer 14

Acetyl groups are added to histones which allows transcription as it leads to the DNA becoming more loosely packed.

Question 15

Tightly packed DNA – strong association between histones and DNA.

Answer 15

Heterochromatin

Question 16

Euchromatin

Answer 16

Loosely packed DNA – weak association between histones and DNA.

Question 17

Tumour

Answer 17

A tumour is mass of identical cells (clones) formed by uncontrolled cell division.

Question 18

Malignant tumour

Answer 18

Tumour which grows quickly and spreads throughout the surrounding tissue, affecting its normal function and so causing harm (e.g. lung cancer reduces elasticity of alveoli). More difficult to treat without damaging the whole tissue.

Question 19

Tumour which grows slowly, remains encased in a capsule and does not spread far eg wart. Removable by surgery or chemotherapy

Answer 19

Benign tumour

Question 20

The spread of tumours to the bloodstream or lymphatic system and can spread to other body parts, causing secondary tumours there-the most difficult to treat.

Answer 20

Metastasis

Question 21

Proto-oncogene

Answer 21

Gene which controls a cell’s division, by stimulating it

Question 22

Gene which controls a cell’s division, by slowing it down

Answer 22

Tumour suppressor gene

Question 23

Two-hit hypothesis

Answer 23

Mutation of both alleles necessary to inactivate tumour suppressor genes ie the reason cancers are often associated with old age (mutation rates are slow so over a longer time, increased chance of two ‘hits’)