Gene expression is controlled by a number of features (20)

Question 1

What are stem cells?

Answer 1

undifferentiated cells that can divide indefinitely and turn into other specific cell types

Question 2

What happens to totipotent cells during embryonic development?

Answer 2

certain parts of the DNA are selectively translated so that only some genes are switched on, in order to differentiate the cell into a specific type and form the tissues that make up the foetus

Question 3

What are the 4 types of stem cell?

Answer 3

totipotent
pluripotent
multipotent
unipotent

Question 4

What can totipotent stem cells do?

Answer 4

mature into any cell type including the placenta and embryo

Question 5

What can pluripotent stem cells do?

Answer 5

mature into any cell type excluding placenta and embryo

Question 6

What can multipotent stem cells do?

Answer 6

can differentiate to a few different types of cell

Question 7

What can unipotent stem cells do?

Answer 7

can only develop into one type of cell

Question 8

What type of cell can unipotent stem cells develop into?

Answer 8

cardiomyocytes

Question 9

What are cardiomycocytes?

Answer 9

heart cells

Question 10

What is the advantage of pluripotent stem cells?

Answer 10

can divide in unlimited numbers so can be used to repair or replace damaged tissue

Question 11

Where are totipotent and pluripotent stem cells found?

Answer 11

in embryos

Question 12

Where are multipotent and unipotent stem cells found?

Answer 12

in mature mammals

Question 13

Which types of stem cell are found in embryos?

Answer 13

totipotent
pluripotent

Question 14

Which types of stem cells are only found in mature mammals?

Answer 14

multipotent
unipotent

Question 15

What is oestrogen?

Answer 15

steroid hormone that affects transcription and is lipid soluble

Question 16

What are 3 uses of stem cells?

Answer 16

• medical therapies e.g. bone marrow transplants, treating blood disorders
• drug testing on artificially grown tissues
• research e.g. on formation of organs and embryos

Question 17

What is a transcription factor?

Answer 17

protein that controls transcription of genes so that only certain parts of DNA are expressed e.g. in order to allow a cell to specialise

Question 18

What are the 3 steps on how transcription factors work?

Answer 18

1) move from cytoplasm to nucleus
2) bind to promotor region upstream of the target genes
3) make it easier or more difficult for RNA polymerase to bind to gene which either increases or decreases the rate of transcription

Question 19

How are induced pluripotent stem cells produced?

Answer 19

from mature, fully specialised (somatic) cells, cell regains capacity to differentiate through the use of proteins, in particular transcription factors

Question 20

What is meant by epigenetics?

Answer 20

heritable change in gene function without change to base sequence of DNA

Question 21

What is the role of tumour-suppressor genes?

Answer 21

code for proteins that control cell division, in particular, stopping cell cycle when damage is detected, as well as being involved in programming apoptosis

Question 22

What is the role of proto-oncogenes?

Answer 22

control cell division, in particular, code for proteins that stimulate cell division

Question 23

What are the 4 steps on how oestrogen works?

Answer 23

1) lipid soluble so easily diffuses through phospholipid bilayer
2) in cytoplasm, binds to a transcription factor called oestrogen receptor
3) forms oestrogen-oestrogen receptor complex
4) complex enters nucleus and acts as transcription factor to facilitate binding of RNA polymerase

Question 24

How is oestrogen linked to cancer?

Answer 24

can be involved in the development of breast cancer as it activates RNA polymerase, so in areas with high oestrogen levels, cell division can become uncontrolled

Question 25

What is an example of a place with high oestrogen levels?

Answer 25

adipose tissue in the breasts

Question 26

What happens in RNA interference?

Answer 26

RNA molecules inhibit gene expression, usually be destroying mRNA so that it cannot be translated

Question 27

Where does RNA interference occur?

Answer 27

in eukaryotes and some prokaryotes

Question 28

What are the 3 steps on how tumour-suppressor genes can be involved in causing cancer?

Answer 28

1) mutation in gene could code for nonfunctional protein 2) hypermethylation and low acetylation could prevent transcription 3) cells divide uncontrollably resulting in a tumour

Question 29

What is the word for high methylation?

Answer 29

hypermethylation

Question 30

What is the word for low methylation?

Answer 30

hypomethylation

Question 31

What are the 3 steps on how proto-concogenes can be involved in causing cancer?

Answer 31

1) mutation in gene could turn into permanently activated oncogene 2) hypomethylation and high acetylation causes excess transcription 3) cells divide uncontrollably resulting in a tumour

Question 32

What are 5 characteristics of malignant tumours?

Answer 32

- rapid, uncontrollable growth - ill-defined boundary - cells do not retain function and often die - spreads quickly and easily - difficult to treat

Question 33

What are the 2 types of tumour?

Answer 33

malignant tumours benign tumours

Question 34

What are 5 characteristics of benign tumours?

Answer 34

- slow growth - defined by clear boundary due to cell adhesion molecules - cells retain function and normal shape - don't spread easily - easy to treat

Question 35

How do epigenetic changes affect humans?

Answer 35

can cause disease either by over activating a gene's function (such as cancer) or suppressing it

Question 36

What are 2 uses of epigenetics?

Answer 36

- treat various diseases - develop ways to reverse epigenetic changes

Question 37

What are the 3 steps on how hypermethylation of DNA affects gene transcription?

Answer 37

1) involves addition of a methyl group to cytosine bases which are next to guanine 2) prevents transcription factors from binding 3) therefore gene transcription is suppressed

Question 38

What is the consequence of abnormal methylation?

Answer 38

can cause cancer as hypermethylation of tumour suppressor genes and oncogenes can impair their function, causing cell to divide uncontrollably