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Section 8 Flashcards

1
Q

Give two characteristic features of stem cells

A

They will keep dividing so they can replace themselfes
They start off undifferentated then can differentate into other cell types

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2
Q

Describe the 3 new types of mutation

A

Duplication - doubling a base
Inversion - a section of a base sequence is inverted
Translocation - moving a section of base sequence to another part of the DNA

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3
Q

What is a totipotent cell?

A

Can differentiate into any body cell
Only present into mammalian embryos for a short time
During development they translate only part of their DNA resluting in cell specialisation

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4
Q

What is a pluripotent cell?

A

Found in embryos
Can differentiate into many different cell types (not embryonic) and can be used to treat human disorders

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5
Q

What is a multipotent cell?

A

can differentiate into many cell types within the same system

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6
Q

What is a unipotent cell and give an example

A

can only differentiate into one cell type e.g cardiomycetes in the heart

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7
Q

What are induced pluripotent cells?

A

produced from somatic cells using transcription factors

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8
Q

What are the advanatges of using induced pluripotent cells for genetic engenering?

A

Not taken from embryos and no risk of rejection as the cell is taken from the host body

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9
Q

What is potency?

A

a measure of how many types of specialised cells a stem cell can make

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10
Q

What is the difference between adult and embryonic stem cells?

A

Adult - can only differentate into cells within their type (e.g blood cells differentiating into different types of blood cell)
Embryonic - can differentiate into any cell type

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11
Q

What is epigenetics?

A

the process which enviromental factors cause heritable changes in gene function without changing the base sequence of DNA

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12
Q

What is a nucleosome?

A

When DNA is wrapped around histones

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13
Q

What is the epigenome?

A

Chemical tags on the nucleosome creating the shape of the DNA histone complex

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14
Q

What does RNA polymerase do?

A

binds RNA nucleotides together in phosphodiester bonds and catalyses the condensation reactions

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15
Q

What is a promoter?

A

a sequence of bases on the DNA strand where RNA polymerase binds to start transcription

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16
Q

What is a transcription factor?

A

Proteins that help RNA polymerase bind to DNA
They activate RNA polymerase and bind to the promoter
Made in the cytoplasm and travels to the nucleus

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17
Q

What is RNA interference?

A

the process of targeting mRNA using small RNA molecules so its not translated, genes are silenced so protein isn’t made

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18
Q

What is SiRNA?

A

Small interfering RNA, short double stranded, has to be fully complimentary to mRNA for hydrolysis by binding to the mRNA within RISC

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19
Q

What is miRNA?

A

mirco RNA, hair pin loop of RNA, not fully complimentary to mRNA so can bind to several mRNA for hydrolysis - binds to RISC by complimentary base pairing

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20
Q

What is RISC and what does it do?

A

An enzyme which which forms RNA induced silencing complexs
Breakes siNRA into seperate strands, one attaches and the other is discarded
The complex binds to mRNA casuing RISC to cut mRNA in two

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21
Q

What does RNA hydrolase/ nuclease do?

A

breaks down mRNA into nucelotides so can’t be translated

22
Q

What is histone acetylation?

A

Amino acids at the tails of histones can be chemically modified by adding acetyl groups
This causes the DNA to become less condensed giving easier acsess to transcription factors leading to more transcription (the genes become more active)
Removal of acetyl groups (deacetylation) from histones will inactivate genes

23
Q

What is DNA methylation?

A

Cytosine bases in DNA can be methylated making it so transcription factors can’t bind and transcription is inhibited

24
Q

Describe what happens in RNA interference

A

Small interfering RNA (SiRNA) binds to a protein called RISC and it breaks the double stranded SiRNA into seperate strands
One strand binds to RISC and the other is discarded
The RISC RNA complex binds to mRNA molecules in the cytoplasm by complimentary base pairing
This binding causes RISC to cut the mRNA in two so it can no longer be used in translation

25
What are the applications of SiRNA?
Can be used to silence genes SiRNA is made in the lab complimentary to the gene wanted to be silenced This can then identify gene functions, genetically modify plantsby getting rid of unwanted genes, silencing cancer genes
26
How is RNA interference used in the body?
Defence against viral attack
27
Describe the action of Oestrogen in translation
Steriod hormones enter the cell by diffusing across the membrane - they can do this because they are lipid soluble Inside the cell the hormone binds to a receptor protein The hormone - receptor complex enters the nucleus Where it binds to the promotor region of a specific gene and acts as a transcription factor And stimulates RNA polymerase to start transcription Which produces the mRNA which is then translated to make the protein encoded by the gene
28
How can altered DNA lead to cancer?
DNA is altered by mutation which changes the base sequence of a gene that controlls cell division This gene could be an oncogene or a tumor supressor gene An oncogene codes for a protein which stimulates cell division so mitosis is uncontrolled If a tumore supressor gene mutates a non functional protein is made so mitosis becomes uncontrolled which leads to a malignant tumor forming
29
What are oncogenes?
Mutated proto oncogenes (dominant) They mutate so it is permanently active and cell division is uncontrolled It may code for a growth factor receptor that is permanently active or a growth factor which is produced excessively
30
What are proto oncogenes?
They code for proteins which are involved in stimulating a cell to divide in response to a growth factor
31
What does a growth factor do?
Binds to a cell surface receptor A series of events occur which lead to the activation of genes controlling DNA replication and cell division
32
What is a tumor supressor gene?
Recessive gene Slows down cell division Repairs mistakes Regulates apoptosis
33
What happens when tumor supressor genes mutate?
If the gene is switched off by mutation the cell can divide uncontrollably
34
Fill in the gaps Increased methylation of DNA _____ genes and ______ transcription If tumor supressor genes are incativates cell division is ______ Decreased methyation of DNA ______ genes and ______ transcription Proto oncogenes become _______ If oncogenes are activated cell division is _______
inactivates prevents increased activates stimulates oncogenes increased
35
How do restriction endonucleases work?
They cut double stranded DNA molecules at a specific recognition site Makes a staggered cut breaking phosphodiester bonds making sticky ends (unpaired bases at the end)
36
What does DNA ligase do?
Joins fragments of DNA together by their sticky ends creating a recombinant piece of DNA Reforms phosphodiester bonds
37
How does reverse transcriptase make DNA using mRNA as a template?
Reverse transcriptase makes a strand of complimentary DNA from the mRNA mRNA is degraded A strand of complimentary DNA is made by DNA polymerase
38
Describe how a gene machine works
The desired DNA sequence is put into a computer The computer designs short overlapping sequences of bases called oligonucleotides A machine supplied with chemical reagents make the sequences in the right order Chemicals are added to make sure the nucleotides join at the right points The short sequences are joined to make longer sequences
39
Describe gene cloning using plasmids
A desired gene is isolated from the human cell Human DNA and plasmid are treated with the same restriction enzyme to make identical sticky ends Mix DNAs together and add DNA ligase Add new DNA into bacteria culture
40
What are the conditions for bacteria to take up new DNA?
Calcium chloride treatment and heat shock
41
Give two examples of marker genes and how they work
The new DNA has antibiotic resistance so ones without will die if treated The new DNA has the GFP gene added to it and under UV it glows green
42
Describe how the polymerase chain reaction happens
Strand separation - Heat to 93degC - this separates the strands and H bonds are broken Primer binding - Add primers and cool to 55degC - Primers are made in the gene machiene and are short sequences of single stranded DNA complimentary to the ends of the DNA being amplified Strand synthesis - Add heat stable DNA polymerase and free nucleotides and heat to 72degC -Complimentary strands of DNA are made by DNA polymerase - 2 new strands made from one - the cycle is repeated by changing the temp
43
What is the point of PCR?
produces larger numbers of identical copies of double stranded DNA Very small amount of DNA can be used
44
What are the uses of PCR?
To copy small amounts in forensic smaples so it can be used in genetic finger printing Genetic screening Detection of bacteria of viruses when present in small numbers
45
What is the problem with PRC?
Very sensitive - the wrong DNA may be copied if the sample is contaminated
46
Describe the process of genetic profiling
Use PCR to amplify the DNA DNA is cut into fragments using restriction endonucleases The fragments are seperated using gel electrophoresis which seperates fragments according to size and charge DNA transfererd to a filter sheet and made into single strands A probe is added which is radioactive so it can be detected This identifies VNTRs within DNA fragments A pattern of bands is formed that is unique to every individual
47
What is a gene probe?
A short sequence of single stranded DNA with a label e.g radioactive isotopes or fluroescent
48
What are VNTRs?
Variable number tandem repeates Aka mini satellites Short sequences of bases that repeate themselves over and over again They differe in people by the number of repeates and the types of them
49
What are some uses of genetic modification?
GM organisms to produce human proteins/ drugs for medical use (insulin) GM plants for more yeild, more nutrition, make their own pesticides, toleratant of extreme conditions
50
What are some risks/ ethical issues around genetic modification?
effects biodiversity and food chains if pests are killed antibiotic resistance using viruses as vectors may cause disease might switch on/ off other genes designer babies playing God animal rights

Biology (8 decks)

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