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topic 8 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are the different gene mutations

A

-inversion
-translocation
-duplication
-substitution

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2
Q

describe inversion

A

a segment of a chromosome is reversed end to end

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3
Q

describe translocation

A

chromosomes and their genes change positions within or between chromosomes

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4
Q

describe duplication

A

part of a chromosome is replicated or duplicated

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5
Q

describe substitution

A

one or more bases in the DNA sequence are replaced by different bases

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6
Q

what is a mutagenic agent and give examples

A

-they increase the frequency of mutations above the rate of naturally occurring mutations
-they are physical or chemical agents that change the genetic material of an organism
e.g. x-rays, UV light

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7
Q

what is a nonsense mutation

A

leads to the stop codon being coded for. polypeptide chain stops being formed

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8
Q

what is a missense mutation

A

results in a different amino acid being coded for. may or may not lead to a different polypeptide chain being produced

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9
Q

what is a silent mutation

A

codes for the same amino acid, as the genetic code is degenerate. doesn’t affect the polypeptide chain

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10
Q

what is a non-disjunction mutation

A

gamete will have either 1 less or 1 more chromosome

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11
Q

what is epigenetics

A

heritable changes in gene function, without changes to the base sequence of DNA - caused by changes in the environment

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12
Q

what is DNA methylation

A

increased methylation inhibits transcription
changes structure of DNA molecule by adding methyl groups. prevents binding of transcription factors and RNA polymerase as it is no longer complementary. this reduces gene expression

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13
Q

what is histone acetylation

A

decreased acetylation inhibits transcription
makes histone more negatively charged so it is less attracted to the negative DNA molecules. there will be less affinity between the histone and DNA
This causes the DNA to be less tightly wrapped so RNA polymerase and transcription factors can more easily bind and therefore gene expression is stimulated

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14
Q

totipotent stem cells

A

can divide and produce any type of body cell.
only occur for a limited time in early embryos.

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15
Q

pluripotent stem cells

A

can become almost any type of cell
used in research to treat human disorders

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16
Q

issues related to pluripotent stem cells

A

-treatment sometimes doesn’t work
-may continually divide to create tumours
-ethical debates about destroying the embryo

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17
Q

multipotent stem cells

A

-can be found in bone marrow
-can differentiate into a limited number of cells

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18
Q

unipotent stem cells

A

-can only differentiate into one type of cell

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19
Q

sources of stem cells in mammals

A

-embryos (pluripotent)
-umbilical cord blood (multipotent)
-placenta (multipotent)
-bone marrow (multipotent)

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20
Q

what are induced pluripotent stem cells used for

A

used to overcome some of the ethical issues of embryonic stem cells

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21
Q

how are induced pluripotent stem cells made

A

-created from adult unipotent cells
-transcriptional factors switch on genes that return the unipotent cells to a state of pluripotency by attaching to gene/promoter region and stimulate/inhibit transcription
-can divide indefinitely
-do not cause the destruction of an embryo

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22
Q

tumour suppressor genes

A

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

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23
Q

what are transcription factors

A

a protein that controls the transcription of genes by binding to a specific region of DNA

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24
Q

what is the promoter region of a gene

A

a section of DNA that is the binding site for proteins that control the expression of the gene, including:
RNA polymerase
Transcription factors

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25
Q

describe oestrogen

A

-a steroid hormone that can initiate transcription
-binds to a receptor site on the transcriptional factor and changes its shape slightly to make it complementary to the DNA so it can bind and initiate transcription

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26
Q

how does siRNA work

A

-enzyme cuts mRNA into siRNA
-one strand of siRNA combines with another enzyme
-the siRNA-enzyme complex will bind to another mRNA molecule through complementary base pairing
-the enzyme will cut up the mRNA so it cannot be translated

27
Q

what are oncogenes

A

genes that have the potential to cause cancer

28
Q

DNA in tumour cells

A

DNA in human tumour cells have changes in DNA methylation and histone acetylation which causes tumour suppressor genes to be silenced and oncogenes to be activated
This leads to deregulation of the cell cycle and the formation of tumours

29
Q

how can siRNA be used in cancer treatment

A

siRNAs can be used in cancer treatment by targeting oncogenes that have been expressed
This reduces the number of proteins produced that can lead to cancer or that maintain cancerous growth

30
Q

Proto-oncogenes

A

produces proteins that stimulate cell division and can cause cancer if mutated.

31
Q

Oncogenes

A

formed from mutated proto-oncogenes and are
permanently switched on resulting in uncontrolled cell division

32
Q

reverse transcriptase

A

catalyses the formation of a strand of complementary DNA from a single strand of RNA. this means the cDNA is intron free.

33
Q

Restriction endonucleases

A

Cut DNA at specific sequences which it is complementary to (recognition sequence). They may cut DNA to leave sticky ends or blunt ends

34
Q

why are sticky ends useful

A

Sticky ends are important because if the same restriction endonuclease is used to cut two DNA fragments then the ends will be complementary. This allows them to attach together.

35
Q

gene machine

A

the protein is examined so the amino acid sequence can be identified and from that, so can the DNA and mRNA sequence.
this is entered into a computer which creates small sections of overlapping single strands of nucleotides that make up the gene called oligonucleotides.
they can then be joined to create the DNA for the gene
PCR can be used to amplify the quantity

36
Q

advantages and disadvantages of reverse transcription

A

adv- mRNA present in cell is from actively transcribed genes so lots of mRNA available to produce cDNA.
dis- more steps so more time consuming and difficult

37
Q

advantages and disadvantages of restriction endonucleases

A

adv-sticky ends on DNA fragments make it easier to insert to make recombinant DNA
disadv- still contains introns

38
Q

advantages and disadvantages of gene machines

A

adv- can design exact DNA fragment you want
disadv- need to know the amino acid/ base sequence

39
Q

promoter region

A

added to the start of a DNA fragment. it is the binding site for RNA polymerase to enable transcription to occur

40
Q

vector

A

carries the isolated DNA fragment into the host cell

41
Q

how is DNA inserted into a vector

A

the plasmid is cut open using the same restriction endonuclease used to cut the DNA fragment. This creates the same sticky ends.
therefore, the sticky ends of the DNA fragment are complementary to the sticky ends on the plasmid
the DNA fragment and the cut plasmid are combined and DNA ligase anneals them by catalysing the formation of phosphodiester bonds between nucleotides

42
Q

how is the vector inserted into the host cell

A

to increase the permeability, the host cells are mixed with Ca2+ and heat shocked.
this enables the vector to enter the host cell’s cytoplasm

43
Q

why might the host cell not take up the recombinant plasmid

A

-the recombinant plasmid might not get inside the cell
-the plasmid rejoins before the DNA fragment enters
-the DNA fragment sticks to itself rather than inserting into the plasmid

44
Q

what are marker genes

A

they identify which bacteria successfully took up the recombinant plasmid

45
Q

what is genetic fingerprinting for

A

the analysis of VNTR DNA fragments. used to determine genetic relationships and the genetic variability within a population

46
Q

examples of samples for genetic fingerprinting

A

blood, body cells, hair follicles.
if the sample is small, PCR is used to amplify the amount of DNA

47
Q

describe gel electrophoresis

A

-restriction endonucleases are added to cut the DNA into smaller fragments.
-the DNA samples are loaded into wells in agar gel.
-the gel is placed in a buffer liquid with an electrical voltage applied
-DNA is negatively charged so the DNA samples move through the gel towards the positive end of the gel
-different lengths of DNA (VNTRs) are separated as smaller pieces of DNA travel further and faster along the gel
-an alkali is used to separate the DNA strands

48
Q

what are DNA probes

A

short single-stranded pieces of DNA, complementary in base sequence to the VNTRs
they are radioactively or fluorescently labelled.
different DNA probes are mixed with the single stranded DNA VNTRs on the agar gel for them to bind

49
Q

what is PCR used for

A

to amplify fragments of DNA in vitro

50
Q

what are DNA primers

A

short, single strands of DNA complementary to the start of the target sequence in PCR. they indicate which sections of DNA should be amplified in PCR

51
Q

how does PCR work

A

the temperature is initially 95 to break H bonds and separate the DNA into single strands
it is then decreased to 55 so primers can anneal
the temperature is then increased to 72, the optimum temp for taq DNA polymerase to attach complementary free nucleotides which makes a new strand to align to each template

52
Q

what are the advantages of PCR

A

-automated
-rapid
-doesn’t require living cells

53
Q

how to locate specific alleles of genes

A

-DNA base sequence must be known to make the complementary DNA probe
-the fragment of DNA can be produced using a gene machine
-the fragment can be amplified using PCR
-a fluorescent or radioactive label is added
-add DNA probes and wash to remove any unbound DNA probes
-presence of radioactive/fluorescent label indicates presence of allele of interest

54
Q

what is genetic screening used for

A

to screen for potential genetic disorders or the presence of disease-causing oncogenes

55
Q

advantages of genetic screening

A

to determine the best dose which increases effectiveness, safety and can save money

56
Q

what is genome sequencing

A

working out the DNA base sequence for all of the DNA in a cell

57
Q

sequencing the genome of simple organisms

A

-no introns so the proteome can be determined directly from the genome

58
Q

what is cancer

A

a result of mutations in genes that regulate mitosis.
if mitosis is not regulated, cells may uncontrollably divide, creating a tumour

59
Q

benign tumours

A

do not tend to cause much harm apart from light damage caused by pressing against blood vessels or other cells. Benign tumours grow slowly and do not spread

60
Q

malignant tumours

A

grow rapidly and can spread to the neighbouring cells via metastasis (through the blood stream or
lymphatic system) thus causing damage by disrupting the running of important processes.
Malignant tumours are difficult to treat in comparison to benign tumours.

61
Q

proto oncogenes

A

stimulate cells to divide by producing proteins that stimulate cell division and can cause cancer if mutated.

62
Q

Abnormal methylation of tumour suppressor genes and oncogenes

A

increased methylation plays an important role in controlling tumour suppressor genes and oncogenes. The hyper-methylation of a tumour suppressor gene
called BRAC1 can lead to breast cancer.

63
Q

Increased oestrogen concentrations

A

can be linked to breast cancer development. These elevated levels are found in fatty tissues the breast. Oestrogen binds to the transcription factor which activates the genes promoting cell division, leading to tumour formation.

64
Q

how to make a radioactively labelled DNA probe

A

-extract DNA and add restriction endonucleases
-separate fragments using gel electrophoresis
-treat DNA to form single strands
-probe binds to gene of interest
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Biology (9 decks)

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