Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology A-Level > Genetic Technology (Chapter 19) > Flashcards

Genetic Technology (Chapter 19) Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is the aim of genetic engineering?

A

To remove a gene(s) from one organism and transfer it to another so that the gene is expressed in its new host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is DNA that has been altered by genetic engineering called?

A

rDNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is recombinant DNA (rDNA)?

A

DNA made by joining pieces from two or more different sources

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a genetically modified organism(GMO)/transgenic organism?

A

The organism which expresses the new gene(s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does genetic engineering provide?

A

A way of overcoming barriers to gene transfer between species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the stages of gene transfer?

A

1) the required gene is identified - may be cut from a chromosome/made by mRNA by reverse transcription/synthesised from nucleotides
2) multiple copies of the gene are made using PCR
3) the gene is inserted into a vector (e.g. plasmid) which delivers the gene to the cells of the organism
4) the vector takes the gene into the cells
5) the cells that have the new gene are identified and cloned

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the 3 tools needed for genetic engineering?

A

1) enzymes - restriction endonucleases/reverse transcriptase/ligases
2) vectors - plasmids/viruses
3) genes coding for easily identifiable substances that can be used as markers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are restriction endonucleases (REs)?

A

A class of enzymes which recognise and break down the DNA of bacteriophages (viruses) by cutting the sugar-phosphate backbone of DNA at specific places within the molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the role of REs in bacteria?

A

To resist a viral infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do REs work?

A

1) they bind to a specific target/restriction site (a sequence of bases) on DNA and cut at that site
2) they either cut straight across the sugar-phosphate backbone to give blunt ends or cut in a staggered fashion to give sticky ends

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are many REs?

A

Palindromic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is bacterial DNA protected from REs?

A

By chemical markers or by not have having the target site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are sticky ends?

A

Short lengths of unpaired bases which can easily form H-bonds with complementary sequences of bases on other pieces of DNA with the same restriction enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why is gel electrophoresis needed to find a specific piece of DNA?

A

Because when long pieces of DNA are cut with a restriction enzyme, there will be a mixture of different lengths

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a plasmid?

A

A small, circular piece of double-stranded DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are 4 characteristics of plasmids?

A

1) they are used as vectors
2) they occur naturally in bacteria
3) they can be exchanged between different bacteria
4) they often contain genes for antibiotic resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How are plasmids obtained from bacteria?

A

1) the bacteria containing them are treated with enzymes to break down their cell walls
2) the ‘naked’ bacteria are then spun at a high speed in a centrifuge so that the relatively large bacterial chromosomes are separated from the much smaller plasmid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How is a gene inserted into a plasmid?

A

1) the circular DNA of the plasmid is cut open with a restriction enzyme
2) opened plasmids and lengths of DNA are mixed together
3) some of the plasmid sticky ends pair up with the sticky ends on the new gene
4) DNA ligase is used to link together the sugar-phosphate backbone of the DNA molecule and the plasmid, producing a closed circle of double-stranded DNA, containing the new gene (recombinant DNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why does the same restriction enzyme need to be used to cut the gene and the plasmid?

A

So that the sticky ends are complementary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What has to be done if the restriction enzyme used gives blunt ends?

A

The sticky ends need to be attached to both the gene and the plasmid DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What characteristics of plasmids make them good vectors or are modified to make them good vectors?

A

1) they have a low Mr - are readily taken up by bacteria
2) they have an origin of replication - can be copied
3) they have several single target sites for different REs in a short length of DNA called a polylinker
4) they have one or more marker genes, allowing identification. Of cells that have taken up the plasmid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How else can plasmids be obtained?

A

They can be made artificially

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How are recombinant plasmids inserted into bacteria?

A

The bacteria are treated by putting them into a solution with a high [Ca2+], then cooled and then given a heat shock to increase the chances of plasmids passing through the cell surface membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens to the bacteria after they are treated with the plasmids?

A

Roughly 1% of the bacteria take up the plasmids with the desired gene (are transformed) and the rest take up plasmid without the gene or no plasmid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How are the bacteria containing the recombinant DNA identified? (old method)

A

1) spread the bacteria on agar plates, each containing an antibiotic
2) any plasmid with a gene won’t be able to grow bc the plasmid contains antibiotic resistance genes
3) ∴ only bacteria with the plasmids survive
4) to identify recombinant bacteria, use a replica plate containing agar with second antibiotic
5) the bacteria containing the desired gene will not grow as the 2nd resistance gene has been inactivated by the insertion of the new gene
6) ∴ identify the colonies on the first plate that did not grow on the second plate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What happens once the bacteria with the recombinant DNA are identified?

A

1) DNA polymerase copies the plasmids
2) the bacteria divide by binary fission so that each daughter cell has several copies of the plasmid
3) the bacteria transcribe the new gene and may translate it to give the required gene product e.g. insulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the concern with using the antibiotic resistance gene as a marker?

A

The gene could spread to other bacteria, leading to untreatable diseases caused by pathogenic bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are two alternatives to using the antibiotic resistance gene as a genetic marker?

A

1) enzymes that produce fluorescent substances e.g. GFP

2) enzyme beta-glucuronidase (GUS) from E.coli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How can the enzyme which makes the protein GFP (green fluorescent protein) be used as a genetic marker?

A

1) the gene for the enzyme is inserted into the plasmid
2) shine UV light on the bacteria
3) the bacteria which glow green are the bacteria which have taken up the recombinant plasmid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How can GUS enzyme be used as a genetic marker?

A

1) any transformed cell with this enzyme, when incubated with some specific colourless or non-fluorescent substrates, can transform them into coloured (blue)/fluorescent products
2) ∴ can see which part of plant expresses the desired genes and can check if gene transfer was successful
3) GUS marker is easy to use and see compared with antibiotic resistance marker

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How can the presence of a promoter be shown?

A

Not all genes in bacteria are switched on at once - bacteria only make the proteins that are required in the conditions in which they are growing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What does a promoter do? (3)

A

1) it controls the expression of genes
2) allows RNA polymerase/transcription factors to bind to the DNA
3) ensures that the RNA polymerase recognises which of the two DNA strands is the template strand
4) initiates transcription
5) avoids having to try and insert gene near to an existing promoter, which might be difficult or disrupt the expression of an existing gene and in eukaryotes the precise position of a promoter is important
6) need a complementary promoter to switch on the desired gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is a promoter?

A

The region of DNA to which RNA polymerase binds as it starts transcription (the transcription start point in the sequence of nucleotides) that is tissue specific

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What must be inserted with a gene so that it is expressed?

A

The appropriate promoter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What can a promoter ensure?

A

A high level of gene expression

36
Q

What else is needed in eukaryotes before transcription can begin?

A

Transcription factors (various proteins) which bind to the promoter region or to RNA polymerase

37
Q

How is insulin produced using genetic engineering?

A

1) extract mRNA from pancreatic beta cells (the only cells which express the insulin gene as they contained lots of insulin mRNA
2) incubate mRNA with reverse transcriptase, forming single-stranded cDNA (copy DNA)
3) convert the single-stranded cDNA molecules to double-stranded DNA molecules using DNA polymerase to assemble nucleotides, making the complementary strand
4) created sticky ends using restriction enzyme
5) mix the cDNA with plasmids and use DNA ligase to insert the cDNA into the plasmid at complementary sticky ends

38
Q

What are the advantages of producing insulin by genetic engineering?

A

1) reduced risk of rejection
2) more rapid response
3) identical to human insulin
4) no ethical issues
5) cheaper to produce in large volume/unlimited availability
6) less risk of transmitting disease
7) good for people who have developed tolerance to animal insulin

39
Q

What is gel electrophoresis?

A

A technique that is used to separate different molecules

40
Q

What does gel electrophoresis involve?

A

1) load DNA fragments created by restriction enzymes into wells at the negative end of the gel because the DNA is attracted to the anode due to phosphate groups of DNA, which give a negative charge
2) add a buffer
3) separation is due to the electric field applied
4) short fragments of DNA move further

41
Q

What does the movement of charged molecules within the gel in response to the electric field depend on? (3)

A

1) net (overall) charge of molecules
2) size of molecules
3) composition of the gel

42
Q

How does the net charge of molecules affect their movement in gel electrophoresis?

A
  • Negatively charged molecules move towards the anode
  • Positively charged molecules move towards the cathode
  • Highly charged molecules move faster than those with less net charge
43
Q

How does the size of molecules affect their movement in gel electrophoresis?

A

Smaller molecules move through the gel faster than larger molecules

44
Q

How does the composition of the gel affect the movement of molecules in gel electrophoresis?

A

The size of the ‘pores’ within the gel determines the speed with which proteins and fragments of DNA move

45
Q

What is the common gel for proteins?

A

Polyacrylamide

46
Q

What is the common gel for DNA?

A

Agarose

47
Q

What is the charge on proteins dependent on?

A

The ionisation of R groups

48
Q

Usually, what is the net charge of proteins

A

Negative

49
Q

What does whether the R groups are charged depend on?

A

pH

50
Q

What is different when proteins are separated by gel electrophoresis?

A

The procedure is carried out a constant pH using a buffer solution

51
Q

What has gel electrophoresis of proteins been used to separate?

A

Proteins produced by different alleles of many genes
e.g. allozymes (variant forms of enzymes produced by diff alleles) and variants of Hb (variant beta globin can indicate sickle cell allele as makes Hb molecules have slightly lower negative charge)

52
Q

Why do DNA fragments carry a small negative charge?

A

The negatively charged phosphate groups

53
Q

Give two examples of where gel electrophoresis is used

A

1) genetic profiling in forensic science

2) paternity testing

54
Q

How is gel electrophoresis of DNA carried out?

A

1) a region of DNA that is known to vary between different people is chosen - it often contains variable number tandem repeats (VNTR) (variable numbers of repeated DNA sequences)
2) two different restriction enzymes cut the DNA close to the VNTR regions
3) the fragments are selected and multiplied
4) gel electrophoresis takes place and the DNA fragments migrate - when the current is turned off the gel contains DNA fragments in different places
5) to make the fragments visible, a radioactive probe is added to bind to the invisible bands of DNA so they can blacken an X-ray film

55
Q

What is a probe?

A

Short sequences of single-stranded DNA with base sequences complementary to VNTR regions

56
Q

What is polymerase chain reaction (PCR)?

A

A method for rapid production of a very large number of copies of a particular fragment of DNA

57
Q

What happens during PCR?

A

1) DNA is denatured by heating it to 95 degrees from double stranded to single stranded, leaving the bases exposed, by breaking the H-bonds between bases
2) annealing (65 degrees) - primers are attached (anneal) to the start of the DNA strand at the complementary sequence
3) elongation (72 degrees) - taq DNA polymerase attaches to the DNA strand and then uses free nucleotides to synthesise complementary strands (the gene has been copied and forms part of two DNA molecules)
4) once the DNA has been copied, the mixture is heated again, which once more separates the two strands in each DNA molecule, leaving them available for copying again

58
Q

Why is DNA placed in a very thin and small tube in a PCR machine?

A

To allow temperatures to change quickly

59
Q

What is placed in the tube in a PCR machine?

A

1) DNA sample (template DNA)
2) primers
3) buffer solution
4) taq DNA polymerase
5) nucleotides
6) water

60
Q

How is PCR and gel electrophoresis used in forensic science?

A
  • PCR is used to amplify DNA from a very small tissue sample or blood drop left at a crime scene (a single DNA molecule can produce billions of copies of itself in a few hours)
  • Gel electrophoresis is then used to analyse the DNA
61
Q

What is taq polymerase and where is it isolated from?

A
  • It is the first heat-stable DNA polymerase used in PCR

- It is isolated fro, thermophilic bacterium Thermus aquaticus found in hot springs in Yellowstone

62
Q

Why is taq polymerase valuable for PCR? (2)

A

1) it is not destroyed by the denaturation step, so it does not have to be replaced during each cycle
2) its high optimum temperature means that the temperature for the elongation step does not have to be dropped below that of the annealing process - efficiency is maximised

63
Q

How can microarrays be used to compare the genes present in two different species?

A

1) DNA is collected from the two species and cut into fragments
2) the DNA is denatured to give lengths of single-stranded DNA
3) the DNA from one species is labelled with green fluorescent tags and the other with red fluorescent tags
4) when the DNA are mixed together, they hybridise with probes on the microarray (DNA that does not hybridise is washed away)
5) the microarray is inspected using UV light, which causes the tags to fluoresce, indicating that hybridisation has taken place because the DNA fragments are complementary to the probes
6) the microarray is then scanned and read by a computer, indicating what genes are present in both/one/neither species

64
Q

What do the different colour fluorescent spots on a microarray mean?

A

Red/green - DNA from only one species has hybridised with the probes
Yellow - two species have DNA with the same base sequence, suggesting they have the same genes
No colour - no DNA has hybridised with a probe, a particular gene is not present in either species

65
Q

How can microarrays be used to compare which genes are active and their level of activity?

A

By identifying genes that are being transcribed into mRNA

66
Q

How can microarrays be used to compare the mRNA molecules in cancerous and non-cancerous cells?

A

1) the mRNA from the cancerous and non-cancerous cells are collected and reverse transcriptase converts mRNA to c(opy)DNA, whose quantity is increased by PCR
2) the cDNA is labelled with fluorescent tags, denatured to give single-stranded DNA and hybridises with probes on the microarray
3) spots on the microarray that fluoresce indicate the genes that were being transcribed in the cell and the intensity of the light emitted by the spot indicates the level of activity in each gene - high/low intensity = many/few mRNA molecules present in sample

67
Q

What is bioinformatics?

A

The collection, processing and analysis of biological information and data using computer software

68
Q

What does bioinformatics do?

A

1) combines biological data with computer technology and statistics
2) builds up databases and allows links to be made between them

69
Q

What information does bioinformatics hold?

A

1) gene sequences
2) sequences of complete genomes
3) amino acid sequences of proteins

70
Q

What are 3 examples of bioinformatics software?

A

1) Ensembl - eukaryotes
2) Uniprot - proteins
3) BLAST (search tool) - comparing primary biological nucleotide sequences

71
Q

What can happen when a genome has been sequenced?

A

1) comparisons can be made with other known genomes e.g. human with drosophila/plasmodium
2) sequences can be matched and degrees of similarity calculated - close similarities indicate recent common ancestry

72
Q

Why are drosophila a useful model for investigating the effects of genes?

A

They may have similar genes/base sequences for development as humans

73
Q

How is information about the plasmodium genome is being used to find new methods to control the parasite?

A

Being able to read the gene sequences is providing valuable information on the development of vaccines for malaria

74
Q

What is an exon?

A

The coding part of the gene

75
Q

What is an intron?

A

The non-coding part of the gene

76
Q

What two kind of ends does cutting open a plasmid with a restriction enzyme give?

A

Blunt or sticky ends

77
Q

Why are sticky ends preferable?

A

Bc they allow us to insert genes in the correct orientation

78
Q

What enzyme is used to form mRNA from DNA?

A

Reverse transcriptase

79
Q

Where is mRNA for the insulin gene found?

A

In pancreatic beta cells

80
Q

How is GFP (marker gene) used to show successful uptake of a gene for a wanted protein?

A

1) GFP is combined with the gene of interest with a promoter
2) both of the genes are transcribed
3) where the gene of interest is expressed, GFP fluoresces

81
Q

Why is mRNA extracted from pancreatic cells and not DNA?

A

1) large number of copies of mRNA readily available
2) mRNA is only from gene coding for insulin
3) easier than extracting a gene from cell’s DNA
4) introns have already been removed

82
Q

What are the benefits of using eukaryotic cells for genetic engineering over prokaryotic cells?

A

1) promoters are already present

2) they have rough ER and Golgi body so insulin can be modified

83
Q

What is the disadvantage of using a gene that codes for GFP rather than the enzyme which produces GFP?

A

It may not fluoresce very brightly because only a few molecules of GFP are produced

84
Q

How can the presence of a gene be confirmed after carrying out gel electrophoresis?

A

1) compare the position of the fragment with reference DNA (ladder)
2) stain the plate and use UV light to see the position
3) use a DNA probe which is complementary to the DNA sequence

85
Q

What are the advantages of using bacteria for genetic engineering?

A

1) can generate huge amounts of target protein at any time
2) easy to grow as need little nutrients
3) have good selection markerrs
4) no ethical issues
5) have plasmids which are easily modified and inserted

Biology A-Level (44 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions