Cell Differentiation And Gene Expression

Question 1

What do stem cells do?

Answer 1

Differentiate into specialised cells

Question 2

What are stem cells?

Answer 2

Unspecialised cells that develop into tiger types of cell

Question 3

What is the process of cells becoming specialised called?

Answer 3

Differentiation

Question 4

Define totipotency

Answer 4

Ability to produce all cell types (including placenta cells)

Question 5

Define pluripotentcy

Answer 5

Ability to produce all specialised cells except extraembryonic cells

Question 6

Define a cells genome

Answer 6

Entire set of DNA

Question 7

How do cells become specialised

Answer 7

Different genes in DNA become active (expressed)

Question 8

How is it only active genes are expressed

Answer 8

mRNA is only transcribed from active genes

Question 9

Define transcription factors

Answer 9

Proteins that bind to DNA and activate/ deactivate genes by increasing/ decreasing rate of transcription

Question 10

What are the two type of factors

Answer 10

Activators: increase rate of transcription

Repressors: decrease rate of transcription.

Question 11

How do activators work?

Answer 11

Help RNA polymerase bind to DNA and begin transcription

Question 12

How do repressors work?

Answer 12

Preventing RNA polymerase binding

Question 13

Where do transcription factors bind to?

Answer 13

Operator regions near start of target gene

Question 14

Define an operon

Answer 14

Section of DNA that contains a cluster of structural genes

Question 15

Describe continuous variation

Answer 15

Characteristic in a range with no categories

Question 16

Describe discontinuous variation

Answer 16

Distinct categories such as eye colour

Question 17

What causes variation in phenotype

Answer 17

Variation in genotype

Question 18

What is a characteristic controlled by 1/ multiple genes called

Answer 18

1: monogenic (usually discontinuous)

Multiple: polygenic (multiple genes at different loci)

Question 19

How can changes in environment directly affect phenotype?

Answer 19

Epigenetic’s determine is a gene is expressed or not

Question 20

How do epigenetic controls work?

Answer 20

Attaching or removing chemical groups to/from DNA. Alters how easy it is for gene to be transcribed

Question 21

What are two ways epigenetics can work?

Answer 21

1. Increased methylation of DNA depresses a gene

2. Modification of Histones affects gene expression

Question 22

Describe methylation

Answer 22

Methyl group attaches to CpG site on DNA coding for a gene. Prevents transcription factors binding so gene is repressed

Question 23

What are Histones?

Answer 23

Can be highly or less condensed

Question 24

How can how condensed chromatin is affect gene expression

Answer 24

How condensed it is affects accessibility of DNA and whether or not transcription factors can bind

Question 25

How can Histones be modified by epigentics

Answer 25

Addiction or removal of acetyl groups

Question 26

What happens when an acetyl group is added

Answer 26

Histone acetylated, chromatin less condensed so transcription factors can bind, allowing gene to be transcribed (activated)

Question 27

What happens when acetyl group removed?

Answer 27

Chromatin becomes highly condensed and genes in DNA cannot be transcribed as transcription factors cannot bind. Repressed

Question 28

What happens to epigenetic changes in cell division?

Answer 28

Changes to gene expression may be passed on to daughter cells - Methyl groups usually removed (not all) during production of gametes