Gene Expression

Front 1

What is transcription?

Back 1

When a gene is copied from DNA into mRNA using enzyme RNA polymerase.

Front 2

What are transcription factors?

Back 2

For transcription to occur the gene has to be switched on by proteins called transcription factors.

Front 3

What are target genes?

Back 3

The genes they control expression of.

Front 4

How to transcription factors control expression?

Back 4

By controlling the rate of transcription.

Front 5

Why are not all cells affected by oestrogen?

Back 5

Not all cells have oestrogen receptors.

Front 6

What do transcription factors do?

Back 6

Move from cytoplasm to the nucleus and bind to specific DNA sites called promoters.

Front 7

Where are promoters found?

Back 7

Near the start of target genes.

Front 8

How do activators affect the rate of transcription?

Back 8

Stimulate or increase rate of transcription e.g. they help RNA polymerase to bind to the start of the target gene and activate transcription.

Front 9

How do repressors affect the rate transcription?

Back 9

Inhibit or decrease the rate of transcription.

Front 10

What type of a hormone is oestrogen?

Back 10

steroid hormone

Front 11

What does osetrogen do when it reaches the plasma membrane of a cell?

Back 11

Diffuse through the phospholipid bilayer.

Front 12

Why can oestrogen diffuse through the phospholipid bilayer?

Back 12

it is lipid soluble.

Front 13

What does oestrogen do when it is inside the cell?

Back 13

Binds to transcription factor called an oestrogen receptor which is complementary shaped.

Front 14

What does oestrogen form when ir bind to oestrogen receptor?

Back 14

oestrogen-oestrogen receptor complex.

Front 15

What happens to the oestrogen receptor when oestrogen binds to it?

Back 15

The oestrogen changes the DNA binding site on the transcription factor.

Front 16

What is the transcroiption factor that oestrogen binds to called?

Back 16

oestrogen receptor.

Front 17

How does the oestrogen-oestrogen receptor complex enter the nucleus?

Back 17

through nuclear pores

Front 18

What happens when oestrogen-oestrogen receptor complex enters the the nucleus?

Back 18

It binds to specific base sequences on DNA

Front 19

Why are not all cells affected by oestrogen?

Back 19

not all cells have oestrogen receptors

Front 20

What controls gene expression?

Back 20

epigentics and transcriptions

Front 21

What is epigenetics?

Back 21

Heritable changes in gene function, without changes to the base sequence of DNA. These changes are caused by changes in the environment that alter transcription through the removal or attachment of chemical groups to or from DNA or histone proteins.

Front 22

What are two methods used to inhibit transcription?(in terms of epigenetics)

Back 22

Increased methylation of DNA

decreased acetylation of histones

Front 23

Describe increased methylation of DNA?

Back 23

Methylation is when a methyl group is attached to the DNA coding for a gene. The group attaches to the CpG site .Which is where cytosine and guanine base are next to each other in DNA.

Front 24

What is an epigenetic mark?

Back 24

CHemical group that is added or removed from DNA or histone proteins that alters transcription.

Front 25

What affects the attachment of epigenetic marks?

Back 25

changes in the environment.

Front 26

What is the CpG site?

Back 26

Where cytosine and guanine base are next to each other in DNA and linked by a phosphodiester bond. MEthyl group attaches to this site.

Front 27

What group is involved in methylation?

Back 27

-CH3

Front 28

How does increased methylation of DNA prevent gene expression?

Back 28

It changes the structure of DNA so that the DNA-Histone complex is more condensed and the transcription machinery can't interact with the gene.

Front 29

What is the transcriptional machinery?

Back 29

enzymes etc involved in transcription.

Front 30

What is chromatin?

Back 30

Histones with DNA wrapped around.

Front 31

What are histones?

Back 31

proteins that DNA wraps around to form chromatin.

Front 32

What affects the accessibility of DNA in terms of the structure of the chromatin?

Back 32

How condesnsed it is.

Front 33

How can histones be epigentically modified?

Back 33

addition or removal of acetyl groups.

Front 34

Name two examples of epigenetic marks?

Back 34

acetyl group and methyl group.

Front 35

What happens when histones are acetylated?

Back 35

the chromatin is less condensed and the transcriptional machinery can access the DNA allowing the DNA to be transcribed.

Front 36

what is the enzyme that is responsible for removing acetyl groups to make a chromatin more condensed/

Back 36

Histone deacetylase (HDAC)

Front 37

What does HDAC stand for?

Back 37

histone deacetylase

Front 38

What are many diseases e.g. cancer triggered by?

Back 38

Epigenetic changes that cause certain genes to be activated or silenced.

Front 39

Are epigenetic changes reversible?

Back 39

yes

Front 40

Why is it useful that epigenetic changes are reversible?

Back 40

they make good targets for new drugs to combat diseases they cause.

Front 41

What type of drugs are sometimes used in relation to increased DNA methylation?

Back 41

Drugs that stop DNA methylation and therefore stop genes being switched off.

Front 42

What is azacitidine and what does it do?

Back 42

USed in chemotherapy for types of cancer that are caused by increased methylation of tumour suppressor genes. Tumour suppressor genes usually slow cell division, so if they are switched off by methylation, cells are able to divide uncontrollably to form a tumour. Azacitidine inhibits methylation of these genes by inhibiting the enzymes involved in the process.

Front 43

What do tumour suppressor genes do?

Back 43

slow cell division

Front 44

What are the problems of developing drugs that counteract epigenetic changes?

Back 44

These changes take place normally in a lot of cells. It is important to make the drugs as specific as possible.

Front 45

What type of cells do drugs in cancer therapies target?

Back 45

Target dividing cells to avoid damaging normal body cells.

Front 46

What part of protein syntehsis does RNAi affect?

Back 46

translation

Front 47

What does RNAi stand form?

Back 47

RNA interference

Front 48

What is RNAi?

Back 48

Small, double stranded RNA molecules stop mRNA from target genes being translated into proteins in eukaryotic cells.

Front 49

True or false RNAi takes place in prokaryotic cells?

Back 49

false but a similar process to RNAi can also occur in some prokaryotes.

Front 50

What are the molecules called that are involved in RNAi?

Back 50

smaill interfering RNA and microRNA.

Front 51

What is an abbreviation for small interfering RNA?

Back 51

siRNA.

Front 52

What does miRNA stand for?

Back 52

microRNA

Front 53

What type of RNA molecules are siRNA and miRNA?

Back 53

non-coding RNA (as tehy don't code for proteins)

Front 54

What happens to mRNA once it has been transcribed?

Back 54

It leaves the nucleus for teh cytoplasm through nuclear pores.

Front 55

What is siRNA double stranded or single stranded?

Back 55

double stranded, when it associates with proteins it unwinds and one of the single strands is selected and the other is broken down.

Front 56

What happens to double stranded siRNA in teh cytoplasm?

Back 56

It associates with several proteins and unwinds. One of the resulting single strands of siRNA is selected and the other is broken down.

Front 57

What happens to the singl;e strand of siRNA?

Back 57

binds to traget mRNA because they have a base sequence with is complementary.

Front 58

WHy can mRNA no longer be translated after siRNA has bound to it?

Back 58

The proteins associated with siRNA cut the mRNA into fragments.

Front 59

Why does the resulting single stranded siRNA bind to teh target mRNA?

Back 59

They have a base sequence which is complementary.

Front 60

What cuts the mRNA into fragments when it binds to siRNA?

Back 60

proteins associated with siRNA.

Front 61

How is miRNA in plants similar to siRNA?

Back 61

The base sequence of miRNA is complementary to the target mRNA sequence and therefore binding occurs and mRNA is cut up and broken down.

Front 62

How is miRNA in plants similar to miRNA in mammels?

Back 62

Its production is similar to mammalian miRNA. When it is first transcribed it exists as a long folded strand. It is processed into a double strand and then into two single strands by enzymes in teh cytoplasm. One strand associates with proteins.

Front 63

Which is more specific siRNA or miRNA and why?

Back 63

miRNA is less specific as it isn't fully complementary to the target mRNA. It can therefore target more than one mRNA molecule.

Front 64

How is miRNA in mammals made?

Back 64

When miRNA is first transcribed, it excists as a long folded strand. It is processed into a double strand then into two single strands by enzymes in the cytoplasm. One strand assocaiates with proteins and binds to target mRNA in cytoplasm.

Front 65

What do the proteins associated with miRNA do?

Back 65

the miRNA-protein complex physically blocks translation of target mRNA. The mRNA is moved into a processing body, where it can eitehr be stored or broken down.

Front 66

What happens to mRNA when miRNA binds to it?

Back 66

The miRNA-proteins complex physically blocks its translation. It is moved to a procesing body.

Front 67

What happens to mRNA when it is stored?

Back 67

It can be returned and translated at another time.

Front 68

What is the phenotype of an organism the result of?

Back 68

An organism's genotype and the interaction of its genotype with the environment.

Front 69

Why are studies of genetically identical twins extremely useful?

Back 69

As twins are genetically identical, any differneces in phenotype must be due to environmental factors. If a characteristic is very similar in identical twins genetics probably plays more of an important role.