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Biology > Section 8- Gene expression > Flashcards

Section 8- Gene expression Flashcards

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1
Q

What are mis-sense mutations?

A

Incorrect amino acid which may produce a malfunctioning protein

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2
Q

What is a nonsense muation?

A

STOP codon

Truncates protein into something smaller

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3
Q

What is a silent mutation?

A

Not harmful

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4
Q

What is a base duplication?

A

A number of bases are repeated causing a frameshift to the right

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5
Q

What is a base inversion?

A

A number of bases are reveresed

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6
Q

What is translocation mutation?

A

A number of bases are removed from one chromosome and become inserted in a different gene

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7
Q

What is a whole chromosome mutation?

A

Insertion of another chromosome

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8
Q

What are the effects of mutations?

A

Production of new advantageous protein = gain of reproductive advantage

Neutral mutation = no change

Production of disadvantageous protein = fatal or disease causing

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9
Q

What is a stem cell?

A

An undifferentiated cell

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10
Q

What is stem cell diferentiation?

A

Specialising cells

Replaces dead or damaged cells throughout the life of the organsim

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11
Q

What does totipotent mean?

A

A fertilised eff has the potential to form every type of human cell

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12
Q

What does pluripotent mean?

A

Capable of producing all cells derived from a particular germ layer

Restricted number

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13
Q

What is multipotent?

A

Can make a restricted range of related cell types

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14
Q

What is unipotent?

A

Able to make only one cell type

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15
Q

What happens with stem cells in plants?

A

Maintain totipotency in form of meristem cells

Cutting/ tissue culture can be used to produce whole plants or plant organs under the right growth conditions

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16
Q

What percentage of genes are being used at any one time?

A

3-5% of their genes at any given time

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17
Q

What are transcription factors?

A

Proteins which move in from the cytoplasm and bind to DNA at specific sites

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18
Q

What is a promoter region?

A

The specific site on DNA which transcription factor binds to

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19
Q

How do transcription factors activate a gene?

A

Allow RNA polymerase to attach to the DNA chain and start transcription

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20
Q

What is transcription initiated by?

A

RNA polymerase AND transcription factors binding to the DNA

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21
Q

What are transcription factors activated by?

A

Stimulated by hormones or growth factors

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22
Q

How does oestrogen stimulate the expression of a gene?

A

Oestrogen is lipid soluble so diffuses through membrane

It combines with receptor site on the transcription factor (complementary binding)

Causes change of shape to the transcription factor causing it to release the inhibitor molecules

Transcription factor enters the nucleus through a nuclear pore and combines with DNA activating transcription

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23
Q

What are epigenetics?

A

It is the study of heritable changes in gene function that do not involve changes to the base sequence of DNA

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24
Q

What is the epigenome and what it is determined by?

A

It is the combination of chemical tags present on DNA

Determined by environmental factors

25
Q

What do histones allow for?

A

Allow eukaryotic DNA to coil and condense

26
Q

What happens if DNA is tightly wrapped around histones?

A

Genes are inaccessible for transcription

Epigenetic silencing

27
Q

What happens is DNA is loosely wrapped around histones?

A

Genes are accessible and easily transcribed

28
Q

What is acetylation?

A

Adding of acetyl group to histone group

Leads to activation of genes causing DNA to uncoil

Switches gene on

29
Q

What happen when acetyl groups are removed?

A

Gene is inactivated

DNA coils slightly

Gene switched off

30
Q

What is hypo-methylation?

A

Hypo (low) methylation increases transcription

Of cytosine

31
Q

What is hyper-methylation?

A

Hyper (high) methylation inhibits transcription

Of cytosine

32
Q

What can cancer be associated with?

A

Reduced DNA methylation of proto-oncogenes which oncogenes

Increased methylation of promotor regions causing deactivation of tumour suppressor genes

33
Q

What are oncogenes?

A

Acts to promote tumour growth

Mutated proto-oncogenes

34
Q

What are tumour suppressor genes?

A

Prevents formation of tumour by preventing cell cycle

Control cell division by inhibiting the proto-oncogenes, repairing DNA and activating cell death

35
Q

How can diseases be treated with gene expression?

A

Enzymes involved in acetylation or methylation inhibited

36
Q

How can disease be diagnosed with gene expression?

A

Relies on detection of levels of methylation and acetylation relative to ‘normal’ levels

37
Q

What is the effect of siRNA on gene expression?

A
  1. Enzyme cuts double-stranded molecules of RNA into siRNA
  2. siRNA combines with enzyme and is broken down in to separate strands
  3. siRNA molecule guides enzyme to mRNA molecule by complimentary base pairing
  4. Enzyme cuts mRNA into smaller sections
    mRNA can no longer be translated into polypeptide
    Gene is not expressed
38
Q

What does siRNA stand for?

A

Small interfering RNA

39
Q

What are carcinogens and what do they do?

A

Cancer causing agents

Cause changes to genes that control cell division

40
Q

What are benign tumours?

A

Grow slowly but can get very large

Tend to remain as a distinct structure and only affect a specific part of the body

Less likely to be life threatening but can disrupt functioning of organs

Can be removed by surgery alone

41
Q

What are malignant tumours?

A

Grow rapidly and can get very large

Tend to extend into surrounding tissues

Develop own blood and lymph systems

May spread to other areas of the body by metastasis

Treatment may involve radiotherapy and chemotherapy as well as surgery

42
Q

What are proto-oncogenes and what do they control?

A

Stimulate cells division and control rate of cell division

A specific proto-oncogene needs to be switched on by a growth factor or hormone to cause cell to grow and divide

43
Q

What can a proto-oncogene mutate into and what is the result?

A

Can mutate into an oncogene

Results in gene activation in the absence of a growth factor

One copy of a mutated proto-oncogene is enough to stimulate cells to divide out of control

44
Q

What can a tumour suppressor gene mutate into?

A

Can become inactivated

Allows rate of cell division to increase or DNA not to be replicated

Both copies of the gene need to be mutated to cause cancer

45
Q

What are induced pluripotent stem cells?

A

Type of pluripotent cell that is produced from unipotent stem cells

Body cells are genetically altered in a lab to make them have characteristics of embryonic stem cells

No need for embryos
All possible type of specialised cells

46
Q

What is the human genome project?

A

Aim:
To identify all genes in human DNA
Find where each gene is located
Determine sequence of bases

47
Q

What was the estimated cost and time of the human genome project?

A

Time = 15 years - took 13 years

Cost = $3 billion

48
Q

What is whole-genome shotgun sequencing?

A

When researchers cut DNA into small easily sequenced sections and use a computer algorithm to align overlapping segments

49
Q

What is whole-genome shotgun sequencing and how is it used to sequence DNA?

A

Involves researchers cutting the DNA into many small, easily sequenced sections

Then using computer algorithms to align overlapping segments to assemble entire genome

50
Q

What are single nucleotide polymorphisms (SNPs)?

A

Single-base variations in the genome that are associated with disease and other disorders

51
Q

Why is it easy to determine the proteome of prokaryotes?

A

No introns

Only one circular piece of DNA, not associated with histones

52
Q

How can the methylation of tumour suppressor genes lead to cancer?

A

No transcription due to methylation

No control of mitosis

Protein produced prevents cell division

53
Q

What is methylation?

A

Attracting enzymes that can add or remove methyl groups to cytosine

54
Q

What is the DNA-histone complex?

A

Where the association of histones with DNA is weak, the DNA-histone complex is less condensed

DNA is accessible by transcriptional factors

Can initiate production of mRNA, switch on the gene

55
Q

How can hypomethylation cause cancer?

A

Reduced methylation

Occurs in oncogenes, leading to their activation

56
Q

How can increased oestrogen in menopausal women cause cancer?

A

Release inhibitor molecule that prevents transcription causing proto-oncogenes to develop into oncogenes

Oncogenes increase rate of cell division leading to development of a tumour

57
Q

What is the process of genome sequencing?

A

Extract samples of DNA from cells

Cut DNA into sections of varying lengths

Amplify DNA

Sequence short sections of DNA

Place sections in order by matching overlapping regions

58
Q

Why would siRNA only affect gene expression in cells infected with HIV?

A

Only infected cells contain mRNA

59
Q

What are 2 ways in which the structure of siRNA differs from mRNA?

A

siRNA is double stranded

siRNA is smaller

Biology (25 decks)

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