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A-level Biology > the control of gene expression > Flashcards

the control of gene expression Flashcards

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1
Q

Gene mutation

A

change in base sequence of DNA
occurs during DNA replication includes addition, deletion, substitution, inversion, duplication and translocation of bases

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2
Q

Mutagenic agents

A

chemical or radiation that
increases mutation rate

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3
Q

Addition mutation

A

One extra base is added to the DNA sequence
causes all subsequent codons to be altered (frameshift)

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4
Q

Deletion mutation

A

One base is deleted in the DNA sequence.
causes all subsequent codons to be altered (frameshift)

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5
Q

Substitution mutation

A

One base in the DNA sequence is changed
no frameshift
only one codon changes
may have no impact due to degenerate genetic code

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6
Q

Frameshift

A

A change in all the codons after the point of mutation
each base shifts left or right one position

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7
Q

Inversion mutation

A

A section of bases detach from the DNA sequence and re-join inverted
results in different amino acids being coded for in this region

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8
Q

Duplication mutation

A

One base is duplicated at least once in the sequence
causes a frameshift to the right

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9
Q

Translocation of bases
mutation

A

A section of bases on one chromosome detaches and attaches to a different chromosome

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10
Q

Non-functioning protein

A

a protein with a different primary and tertiary structure
therefore the shape is changed it cannot carry out its function

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11
Q

Tumour

A

a mass of cells as a result of uncontrolled cell division
can be benign or malignant

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12
Q

Benign tumour

A

non-cancerous tumour
grows large but at a slow rate
produce adhesive and are surrounded by a capsule so they cannot spread

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13
Q

Malignant tumour

A

cancerous tumour
grows rapidly
can become unspecialised can metastasise
grow projections
develop own blood supply

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14
Q

Metastasis

A

cancer cells breaking off from the tumour
spreading to form secondary
tumours in different tissues or organs

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14
Q

Cancer

A

Malignant tumours that form due to uncontrolled cell division

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15
Q

Oncogene

A

a mutated version of a proto- oncogene
results in constant initiation of DNA replication and mitotic cell division
causes tumour formation

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16
Q

Tumour suppressor genes

A

genes that produce proteins to slow down cell division and cause cell death if DNA copying errors are detected

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17
Q

Epigenetics

A

the heritable change in gene function
without changing the DNA base sequence
caused by changes in the
environment
can inhibit transcription

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18
Q

Hypermethylation

A

an increased number of methyl groups attached to a gene results in the gene being deactivated
results in cancer if happens to a
tumour suppressor gene

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19
Q

Methylation of DNA

A

inhibits transcription
methyl groups attach to the cytosine base on DNA
prevents transcriptional factors from binding
condenses the DNA-histone complex

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20
Q

How can oestrogen increase the risk of breast cancer?

A

Oestrogen is a steroid hormone it binds to a receptor site on a transcriptional factor
causing a change in shape
so it can bind to the DNA to
initiate transcription
can result in uncontrolled cell division

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21
Q

Stem cell

A

undifferentiated cells that can continually divide and become specialised

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22
Q

Totipotent stem cell

A

can differentiate into any body cell
occur for a limited time in early mammalian embryos

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23
Q

Multipotent stem cell

A

can differentiate into a limited number of cells
found in mature mammals e.g in bone marrow

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23
Q

Pluripotent stem cell

A

can differentiate into almost any body cell
occur in embryos

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24
Q

Unipotent stem cell

A

can differentiate into one type of cell
found in mature mammals

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25
Q

Induced pluripotent
stem cell

A

produced from adult somatic cells
using protein transcriptional factors
overcomes ethical issues of using embryonic stem cells

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26
Q

Transcriptional factor

A

proteins that can bind to different base sequences on DNA
initiate transcription of genes

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27
Q

What is a vector?

A

a DNA molecule used as a vehicle to carry a DNA fragment
e.g. plasmids/viruses

28
Q

Acetylation of histones

A

Decreased acetylation inhibits transcription
removing acetyl groups makes the histones more positive this attracts the negative phosphate group on DNA making it harder for the transcriptional factors to bind

29
Q

Sequencing projects

A

Reading the full genome of organisms
provides opportunities to screen DNA to identify potential medical problems

29
Q

RNA interference

A

inhibition of the translation of mRNA
the mRNA gets destroyed so it cannot be translated

30
Q

siRNA

A

small interfering RNA destroys mRNA molecules to prevent translation

31
Q

Recombinant DNA technology

A

combining different organisms’ DNA
enable scientists to manipulate and alter genes to improve industrial processes and medical treatment

32
Q

How can you create a DNA fragment?

A

Reverse transcription with reverse transcriptase restriction endonucleases gene machine

33
Q

Gene machine

A

creates DNA fragments using a computerised machine

34
Q

Restriction endonulceases

A

Enzymes that cut up DNA to create fragments
cut at specific recognition/restriction sequences
results in sticky ends

35
Q

Reverse transcriptase

A

An enzyme that makes cDNA single-stranded copies of DNA from mRNA

36
Q

In vivo cloning

A

Creating DNA fragments using bacteria
involves restriction endonulcease enzymes

37
Q

In vitro cloning

A

Using PCR to create a large number of copies of a DNA fragment

38
Q

Uses of PCR

A

Used widely in gene technology to make large numbers of copies of DNA fragments
e.g. forensics, genotyping, cloning, paternity tests, microarrays

39
Q

Describe the PCR process

A

increase temperature to 95C to break hydrogen bonds & split
DNA into single strands temperature is decreased to 55C so primers can attach
DNA polymerase joins complementary nucleotides & makes a new strand temperature increased to 72C (optimum for Taq DNA polymerase)

40
Q

Uses of genetic fingerprinting

A

Forensic science
medical diagnosis
plant/animal breeding
paternity tests

41
Q

What is gel electrophoresis

A

Separation of DNA samples using an electrical voltage
different lengths of DNA VNTRs are separated

42
Q

Why does the DNA move in gel electrophoresis?

A

DNA is negatively charged and moves towards the positive end of the gel
the shorter the piece of DNA, the faster and further it moves

43
Q

What is genetic screening?

A

Testing DNA to identify the presence of alleles that can cause/increase the risk of developing a disease

43
Q

What is genetic counselling?

A

a type of social work giving people advice and information following the screening of disease causing alleles

44
Q

What is cDNA?

A

Complementary, single- stranded DNA strands
created by reverse transcriptase

45
Q

What are the advantages of using the gene machine?

A

Very quick
accurate
create intron-free DNA

46
Q

What are the advantages of using reverse transcription?

A

Creates intron-free cDNA

47
Q

What are the advantages of using restriction endonculeases?

A

Creates sticky ends on DNA to enable the DNA fragments to join with complementary base pairs

48
Q

Oligonucleotides

A

Short DNA molecules
used in gene machines to create DNA fragments

49
Q

Sticky ends

A

Exposed staggered ends of bases
palindromic base sequences created by restriction endonuclease enzymes

50
Q

Palindromic sequence

A

sequences of bases that read the same forwards as they do
backwards

51
Q

Blunt end

A

When a restriction endonuclease cuts the DNA double-strand in the same position
there is no overhang of bases

52
Q

What are the two methods to amplify DNA?

A

In vivo
in vitro (PCR)

53
Q

Terminator region

A

added at the end of the gene it causes RNA polymerase to detach and stop transcription to ensure one gene is copied into mRNA at a time

53
Q

Promoter region

A

a sequence of DNA that is the
binding site for RNA polymerase
to enable transcription to occur

54
Q

Plasmid

A

a small loop of bacterial DNA contains only a few genes contains the genes for antibiotic resistance

55
Q

Recombinant plasmid

A

a small loop of bacterial DNA with the DNA from another organism inserted into it

56
Q

Transformation

A

the process of getting a plasmid to re-enter a bacterium
involves calcium ions and temperature shocking

57
Q

How can transformed cells be identified?

A

using marker genes antibiotic resistance genes genes coding for fluorescent proteins
genes coding for enzymes

58
Q

What is a marker gene?

A

genes on the plasmid used to identify which bacteria successfully took up the recombinant plasmid

59
Q

DNA probe

A

short, single-stranded pieces of DNA
labelled radioactively or fluorescently so that they can be identified

60
Q

DNA hybridisation

A

DNA is heated to separate the double helix into single strands it is then mixed with complementary sequences of single-stranded DNA
it is then cooled so
complementary strands will anneal

61
Q

Personalised medicine

A

screening for the presence of particular alleles
to select medicines and personalise health advice based on your genotype

62
Q

VNTRs

A

variable number tandem repeats sequences of bases in introns
unique to each person

63
Q

How can DNA samples be collected?

A

From blood, body cells or hair follicles

64
Q

How is DNA extracted from cells so that it can be examined?

A

cell fractionation and ultracentrifugation

65
Q

How is DNA digested in genetic fingerprinting?

A

Restriction endonucleases are added to cut the DNA into smaller fragments
enzymes that cut close to the target VNTRs are added

66
Q

Why can the genome not be easily translated into the proteome in complex organisms?

A

due to the presence of non- coding DNA and regulatory genes

67
Q

What is the role of DNA ligase in making recombinant DNA?

A

used to stick the DNA fragment to create recombinant DNA

A-level Biology (8 decks)

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