Cell differentiation and gene expression

Question 1

Define cell differentiation

Answer 1

The production of different cell types within an organism from one original cell type

Question 2

Define cell determination

Answer 2

When a cell differentiates into a new cell type the process is stable and complex.
The change is not normally reversible even of the signal that indued the change has ceased

Question 3

Define cell lineage

Answer 3

The series of cell types leading from the zygote to a particular cell
Branches are not cell divisions

Question 4

Define modulation

Answer 4

A simple, reversible change in gene expression with no change in cell type

Question 5

Define euchromatin

Answer 5

lightly packed form of chromatin thats rich in genes and often under active transcription

Question 6

Define heterochromatin

Answer 6

tightly packed form of chromatin thats poor in genes and cannot be transcribed

Question 7

What is DNA methylation and where does it occur

Answer 7

Methylation causes folding which blocks transcriptional machinery from assessing DNA
This normally occurs around the promoter or control sequence

Question 8

DNA methylation process

Answer 8

Occurs on a cytosine when the CpG pair is already methylated
Maintenance methyltransferase copies the methylation onto the newly synthesised strands of DNA

Question 9

De novo methylation process

Answer 9

Un-methylated CpG pairs can become methylated via de no methyltransferase
The complementary CpG pair is methylated by maintenance methyltransferase

Question 10

Specific transcriptional regulation of individual genes process

Answer 10

Specific protein transcription factors can bind to DNA, normally on promoters
This either increases or decreases the transcription of a specific gene
This allows for household and luxury genes

Question 11

What is a master gene regulator

Answer 11

Regulates a whole set of lineage-specific genes for a given cell type, can have positive or negative effects on different genes

Question 12

3 patterns of cell divisions in mature differentiated cells

Answer 12

1. Cells may divide very little but can divide to repair damage e.g. endothelium and liver
2. Terminal differentiation - cells that cannot divide e.g. neurones and lens
3. Terminally differentiated cells may be constantly replaced by division of precursor cells called somatic stem cells e.g. bone marrow and epidermis

Question 13

Cell differentiation in cancer

Answer 13

Differentiation is deficient in cancers e.g. tumour cells can resemble precursors like blast cells

Question 14

Cell differentiation in birth defects

Answer 14

Differentiation of a particular cel type is affected