Gene expression - Yr 2

Question 1

Totipotent (or omnipotent)

Answer 1

Cells which can mature into any type of body cell

Question 2

Pluripotent

Answer 2

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

Question 3

Multipotent

Answer 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

Question 4

Induced pluripotent stem cells

iPSCs

Answer 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.

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

Adult stem cells

Answer 8

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

Question 9

Embryonic stem cells

Answer 9

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

Question 10

Transcriptional factors

Answer 10

Specific molecules which move from cytoplasm to nucleus to stimulate transcription

Question 11

siRNA

Answer 11

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

Question 12

Epigenetics

Answer 12

Epigenetics is the study of cellular and physiological traits (and their underlying mechanisms) that are heritable by daughter cells and which result from changes in gene expression that are not due to an alteration in the DNA nucleotide sequence).

Question 13

Methylation

Answer 13

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

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

Heterochromatin

Answer 15

Tightly packed DNA – strong association between histones and DNA.

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

Benign tumour

Answer 19

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

Question 20

Metastasis

Answer 20

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

Question 21

Proto-oncogene

Answer 21

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

Question 22

Tumour suppressor gene

Answer 22

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

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’)

Question 24

Genome

Answer 24

All of the genetic material in an organism.

Question 25

Complete proteome

Answer 25

The full range of proteins coded for by the genome. (Identified by gel electrophoresis and mass spectrometry).

Question 26

Cellular proteome

Answer 26

refers to the proteins produced by a given type of cell under a certain set of conditions.

Question 27

Epigenome

Answer 27

The sum of all the epigenetic changes in a cell.

Question 28

Sanger Sequencing

Answer 28

Initial method of sequencing genomes that requires terminator nucleotides, free nucleotides, primers, DNA polymerase and result in multiple fragments of varying length, which allows the DNA sequence to be determined.

Question 29

Human Genome Project

Answer 29

International scientific research project to determine the nitrogenous base pair sequence which make up human DNA, identifying and mapping all the genes of the human genome

Question 30

Next Generation Sequencing (NGS)

Answer 30

Faster, more recent sequencing methods that are continually developing and becoming more efficient, powerful and cost effective.

Question 31

Whole-genome (shotgun) sequencing

Answer 31

Focuses on sequencing all of the DNA in an organism’s genome by cutting the DNA into many small, easily sequenced sections then uses computer algorithms to align overlapping segments to assemble the entire genome.

Question 32

DNA electrophoresis

Answer 32

Method of separating out negatively charged DNA fragments by applying a current. The smaller fragments will move quicker towards the positive anode.