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Biology - Unit 8 > Chapter 20 - Gene Expression > Flashcards

Chapter 20 - Gene Expression Flashcards

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1
Q

Define mutation

A

A sudden change in the amount or the arrangement of the genetic material in a. cell

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2
Q

Define gene mutation

A

A change to one or more nucleotide bases in DNA resulting in a change in genotype which may be inherited

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3
Q

When may gene mutations arise?

A

During the replication of DNA

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4
Q

What is a substitution of base?

A

A nucleotide in a DNA molecule is replaced by another nucleotide with a different organic base

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5
Q

What are the three consequences of base substitution?

A
  • Formation of stop codon and hence protein synthesis stops
  • Formation of different codon and different acid and hence a possible nonfunctional protein
  • Formation of different codon but same amino acid so no effect
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6
Q

Define frame shift

A

Where a DNA base is deleted ands the reading frame containing each three letters is moved to the left by one

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7
Q

Define deletion of base

A

A loss of a nucleotide from a DNA sequence

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8
Q

Define and describe addition of bases

A

An extra base becomes inserted and frame shift to the right occurs unless n3 bases are inserted

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9
Q

Define and describe duplication of bases

A

Where one or more bases are repeated causing frameshift to the right

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10
Q

Define and describe inversion of bases

A

When a group of bases becomes separated and rejoins the DNA in inverse order causing a reversed effect on the amino acids

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11
Q

Define and describe translocation of bases

A

Where a group of bases become separated and inserted on a different chromosome causing abnormal phenotypes

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12
Q

Define and describe two mutagenic agents

A
  • High energy ionising radiation which disrupt the structure of DNA
  • Chemicals such as nitrogen dioxide disrupt the structure of DNA or interfere with transcription
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13
Q

Why may mutations be “good?”

A

They created genetic diversity necessary for natural selection and speciation

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14
Q

Why may mutations be “bad?”

A

They produce harmful effects and can disrupt cellular activities

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15
Q

What causes a cell to become specialised?

A

Expression of certain genes

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16
Q

Define totipotent stem cell

A

A cell derived from a fertilised egg able to differentiate into any type of cell found in the body and into embryonic cells

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17
Q

Why do cells specialise instead of expressing all genes?

A

Prevent wastage and to carry out functions more effectively

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18
Q

Give the two ways in which genes are prevented from expressing themselves

A
  • Prevention of transcription (no mRNA)

- Prevention of translation

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19
Q

How do stem cells replenish themselves?

A

Self renewal

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20
Q

Give four origins of mammalian stem cells

A
  • Embryonic stem cells
  • Umbilical cord blood stem cells
  • Placental stem cells
  • Adult stem cells
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21
Q

Define pluripotent cell

A

Cells that can differentiate into almost any type of cell but cannot form extra embryonic cells

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22
Q

Define multipotent cell

A

Cells found in adults that can differentiate into a limited number of specialised cells. Examples include adult and umbilical cord stem cells

23
Q

Define unipotent cell

A

A cell derived from multipotent cells that can differentiate into one type of cell

24
Q

What are induced pluripotent cells?

A

Pluripotent cells created from unipotent cells by expressing genes which are currently not expressed

25
Q

What is added to embryonic stem cells to cause them to differentiate in in vitro conditions?

A

Differentiation factors

26
Q

What are transcriptional factors?

A

Molecules that bind to a specific site on DNA to begin the process of transcription

27
Q

Describe how oestrogen regulates transcription

A
  • Lipid soluble so freely diffuses into the cell membrane
  • Binds to receptor on transcription factor and changes shape making it complementary/removes inhibitor
  • Transcription factor moves into nucleus and binds to DNA to start transcription
28
Q

What is epigenetics?

A

Heritable changes in gene function without changes to the base sequence of DNA

29
Q

What is the epigenome?

A

The second layer found in DNA created by the chemical tags on histones

30
Q

Why is the epigenome flexible?

A

The chemical tags on histones can respond to environmental changes

31
Q

Describe how the epigenome is altered

A
  • Environmental signal stimulates proteins to carry messages
  • Protein passes this into nucleus
  • Protein attaches to DNA causing acetylation or methylation
32
Q

What is the effect of acetylation?

A

Activation of gene

33
Q

Describe the consequence of less condense DNA-histone complexes

A

A weak association between DNA and histones leaving DNA accessible to transcription factors

34
Q

Describe the consequences of more condense DNA-histone complexes

A

A strong association between DNA and histones leaving DNA not accessible to transcription factors

35
Q

What is acetylation?

A

The process whereby an acetyl group is transferred to a molecule

36
Q

How is DNA acetylated?

A
  • Acetylecoenzyme A donates an acetyl group to DNA
37
Q

What is the effect of deacetylation on DNA?

A
  • Increases positive charge of histones
  • Increases attraction to phosphate groups
  • Association stronger
  • Not accessible to transcription factors
38
Q

What is methylation of DNA

A

Addition of methyl (CH3) to cytosine bases

39
Q

How does methylation inhibit transcription?

A
  • Prevention of transcription factors binding to DNA

- Attracts proteins that induce deacetylation making DNA inaccessible to transcription factors

40
Q

How can methylation increase the chances of mutations?

A
  • Some genes repair DNA
  • Increased methylation leads to genes being switched off
  • Protein that repairs damaged base sequences not produced
  • Cancer is a consequence
41
Q

What is small interfering RNA (siRNA)?

A

A type of RNA that destroys mRNA before translation

42
Q

How is siRNA produced?

A
  • Enzyme cuts large double stranded molecules of RNA into siRNA
43
Q

How does siRNA prevent translation?

A
  • After siRNA is produced, it combines with an enzyme
  • Bases on siRNA bond with bases on mRNA
  • Enzyme cuts the mRNA into smaller sections
  • mRNA no longer capable of being translated
44
Q

What are proto-oncogenes?

A

Cells that stimulate cells to divide by producing proteins that stimulate cell division

45
Q

How do proto-oncogenes stimulate cell division?

A
  • Produce proteins that stimulate cell division

- Activates genes that cause DNA to replicate

46
Q

What are oncogenes?

A

Mutated proto-oncogenes that produce a permanently activated receptor or code for a growth factor in excessive amounts

47
Q

What are tumour suppressor genes?

A

Cells that control cell division, cause the cell cycle to stop when damage occurs and programme apoptosis

48
Q

What occurs when a tumour suppressor gene mutates?

A

Cell division is not regulated and cells divide rapidly and out of control

49
Q

How does hypermethylation lead to cancer?

A
  • Occurs in specific region of tumour suppressor genes
  • Tumour suppressor gene inactivated
  • Transcription inhibited
  • Hence increased cell division occurs leading to a tumour
50
Q

How can increased oestrogen concentration cause tumour formation?

A
  • Oestrogen binds to transcription factor
  • Activates genes that promote cell division
  • Tumour forms
51
Q

Why are genome projects useful?

A
  • Understand inherited disease
  • More understanding means more medicine and cures
  • More predictions on likelihood of particular disease and so can avoid risk factors
  • Understand evolution
52
Q

Why is it easy to determine the proteome of a prokaryote?

A
  • Majority of prokaryotes have one circular piece of DNA

- No noncoding portions of DNA

53
Q

Why is it useful to know the proteome of pathogens?

A

So we can analyse the antigens and use this for vaccines

Biology - Unit 8 (2 decks)

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