8. control of gene expression Flashcards
MUTATIONS
what’s a mutation?
alteration to the DNA base sequence, often arising spontaneously during DNA replication
MUTATIONS
what’s a addition mutation?
one extra base added to the sequence.
means all subsequent are altered in a FRAMESHIFT
so diff amino acid coded for, can lead to a non-functioning protein.
TAC TTC AGG TGG
TAC ATT CAG GTG G
———————>
MUTATIONS
what’s a deletion mutation?
deletion of a base in a sequence
FRAMESHIFT TO LEFT
diff polypeptide chain produced as diff AA coded for.
TAC TTC AGG TGG
TAC TCA GGT GG
———————>
MUTATIONS
what’s a substitution mutation?
replacement of a base by a different base in DNA- no frameshift.
Only one codon changes and as the genetic code is degenerate it may still code for the same AA (no impact)
TAC TTC AGG TGG
TAC ATC AGG TGG
MUTATIONS
what’s an inversion mutation?
section of bases detach from DNA and when rejoin they are inverted. Diff AA coded for in this region.
FRAMESHIFT
TAC TTC AGG TGG
TAC GGA CTT TGG
MUTATIONS
what’s a translocation mutation?
Section of bases on one chromosome detached and inserted into the DNA of a diff chromosome.
MUTATIONS
what’s a duplication mutation?
where one or more bases duplicate and repeat
FRAMESHIFT
MUTATIONS
which mutations are most like out to have a significant impact and why?
insertion, deletion, duplication, translocation because they produce a frameshift meaning the entire amino acid sequence produced will be diff.
MUTATIONS
what is a mutagenic agent? give examples
factors that increase the rate of gene mutation.
chemical mutagens such as tabasco smoke and alcohol.
Ionising radiation such as UV and X-ray
STEM CELLS
What is a stem cell?
undifferentiated cells that continually divide to become specialised in differentiation
STEM CELLS
name the types of stem cells
totipotent
pluripotent
multipoint
unipotent
STEM CELLS
describe totipotent stem cells
divide to produce any type of body cell including placenta and embryo.
certain parts of the DNA are selectively translated so only some genes are switched on to differentiate the cell into a specific type.
STEM CELLS
describe pluripotent cells
can divide into any type of cell other than placenta and embryo.
can divide into unlimited numbers so can be used to repair or replace damaged tissues.
STEM CELLS
describe multipoint cells
can only divide into a limited number of diff cell types.
found in mature mammals, e.g. in bone marrow
STEM CELLS
describe unipotent cells
A cell that can only differentiate into one type of cell.
only found in mature mammals
STEM CELLS
which type of cells are found in embryos?
totipotent, pluripotent
STEM CELLS
give some uses of stem cells
Medical therapies, e.g. bone marrow transplants, treating blood disorders.
drug testing on artificially grown tissues
REGULATION OF TRANSCRIPTION
what is a transcription factor?
a protein that controls the transcription of genes so that only certain parts of the DNA are expressed (turns on/off gene)
what are induced pluripotent stem cells (IPS)
reprogramming unipotent cells into pluripotent using transcription afford in a lab
REGULATION OF TRANSCRIPTION
how do transcription factors work?
- move from the cytoplasm into the nucleus
- bind to promoter region upstream of target gene
- makes it easier or more difficult for RNA polymerase to bind to gene. This increases or decreases the rate of transcription.
REGULATION OF TRANSCRIPTION
Give an example of a hormone that affects transcription and explain how it works
Oestrogen
can initiate transcription by binding to a receptor site in the cytoplasm
Changes shape so it’s complementary to DNA and can bind and initiate transcription (initiates binding of RNA polymerase)
REGULATION OF TRANSCRIPTION
what are epigenetics?
a heritable change in gene function without change to the base sequence of DNA
REGULATION OF TRANSCRIPTION
how does increased methylation of DNA affect gene transcription?
methyl groups added to DNA, attach to cytosine bases.
This prevents transcription factors binding, so gene transcription is suppressed.
REGULATION OF TRANSCRIPTION
how does decreased acetylation of histones affect gene transcription?
inhibits transcription
CANCER
what are benign tumours
grow at slow rate
non-cancerous - produce adhesion molecules which sticks them together and to a particular tissue
impact = localised (don’t spread easily), can be removed by surgery, rarely return (easy to treat)
CANCER
describe malignant tumours
cancerous, uncontrollable rapid growth.
don’t produce adhesion mols- metastasis occurs where the tutor spreads easily and quickly to other parts of body.
difficult to treat and can be life threatening
CANCER
describe the role of tumour suppressor genes
produce proteins that slow down cell division/cause cell death if damage/ copying errors are detected.
CANCER
explain how tumour-suppressor genes can be involved in developing cancer?
a mutation in the tumour-suppressor gene means they aren’t transcribed
due to the amino acid sequence/tertiary structure being altered.
OR
so the protein isn’t produced that prevents cell division.
This results in uncontrollable cell division.
increased/abnormal/hypermethylation can lead to this too.
CANCER
describe the role of proto-oncogenes
control cell division - in particular code for proteins that stimulate cell division.
CANCER
explain how proto-oncogenes can be involved in developing cancer
mutation in the gene could turn it into a permanently activated oncogene.
This results in uncontrolled cell division and formation of a tumour.
CANCER
explain how abnormal methylation of genes can cause cancer
hyper-methylation of tumour-suppressor genes (methyl groups added) means the transcription of tumour suppressor genes is inhibited, leading to uncontrolled cell division.
(turn the gene off/inactivate)
CANCER
explain how oestrogen can be involved in developing breast cancer
an increase of oestrogen concentration in breast tissue can cause uncontrolled cell division due to it activating RNA polymerase
REGULATION OF TRANSCRIPTION
what can inhibit the translation of mRNA? and how?
RNA interference (RNAi)
or smalll interfering RNA (siRNA)
- an enzyme cuts mRNA into siRNA
- One strand of siRNA combines with another enzyme
- siRNA-enzyme complex will bind via complementary base pairing to another mRNA mol
- enzyme will cut up mRNA so cannot be translated
GENOME PROJECTS
what is the genome?
the complete set of genetic info contained in the cells of an organism.
GENOME PROJECTS
what is the proteome?
the range of different proteins that a cell can produce
GENOME PROJECTS
what is genome sequencing?
identifying the DNA base sequence of an individual
GENOME PROJECTS
can we directly translate the genome onto the proteome?
in simple organisms, yes as they don’t contain introns, but in complex organisms due to the presence of non-coding DNA (introns) and regulatory genes it’s much harder to obtain the proteome.
GENOME PROJECTS
give an application of sequencing the proteome in simple organisms
Identifying potential antigens for use in vaccine production.
GENOME PROJECTS
Determining the genome of the viruses could allow scientists to develop a vaccine. explain how
the scientists could identify the proteome then they could identity potential antigen to use in the vaccine
GENOME PROJECTS
Determining the genome of the viruses could allow scientists to develop a vaccine. explain how.
the scientists could identify the proteome, then they could identify potential antigens to use in the vaccine.
RECOMBINANT DNA
what is meant by recombinant DNA technology?
the transfer of DNA fragments from one organism to another
RECOMBINANT DNA
outline the process of using reverse transcriptase to produce DNA fragments
mRNA complementary to the target gene is used as a template.
it’s mixed with free nucleotides which match up to their base pairs and reverse transcriptase which forms the sugar-phosphate backbone to create cDNA (complementary DNA)
RECOMBINANT DNA
outline the process of using enzymes to produce DNA fragments
restriction endonucleases cut DNA at specific DNA base sequences.
Diff ones cut at different points.
Cut to create staggered ends and exposed DNA bases (sticky ends) - ability to join DNA with complimentary sticky ends.
RECOMBINANT DNA
outline the process of the gene machine
amino acid sequence is determined, then DNA and mRNA sequence is worked out.
DNA sequence is entered into computer which checks for biosafety and security that the DNA created is safe and ethical to produce.
computer forms small sections of single stands of DNA
IN VIVO CLONING
outline the process of in vivo cloning
Restriction endonucleases are used to cut out DNA fragment.
Vector (plasmid) is then cut using the same restriction endonuclease (same sticky ends produced) so means DNA fragments sticky ends are complimentary to sticky ends on plasmid).
DNA ligase joins the DNA fragment and plasmid together (annealing)
Transformation:
vector needs to be inserted into host cell for translation. To make cell membrane of host cell more permeable, it’s mixed with Ca2+ and heat shocked.
IN VIVO CLONING
how do you identify transformed cells?
Marker genes (e.g. coding for fluorescence) can also be inserted into vectors along with the DNA.
When cells begin to grow, UV light can be used to identify which cells have taken up the vector and which haven’t.
GENETIC FINGERPRINTING
How does genetic fingerprinting work?
every organisms genome contains non-coding regions called variable number tandem repeats (VNTRs).
probability of two individuals having same VNTRs is very low so we can compare them to see if two DNA samples come from the same person.
GENETIC FINGERPRINTING
outline the process of genetic fingerprinting analysis up to gel electrophoresis
small sample of DNA is collected. VNTRs cut out using restriction enzymes, labelled, and cloned using PCR.
Fragments are separated using gel electrophoresis.
GENETIC FINGERPRINTING
outline the separating of fragments of DNA in gel electrophoresis
DNA samples are loaded into small wells in agar gel and placed in buffer liquid with electrical voltage applied.
DNA = neg charged so DNA samples move through the gel towards the pos end.
shorter fragments travel further. The pattern of bands created is unique to the individual.
GENETIC FINGERPRINTING
give applications of genetic fingerprinting.
forensic science - to place suspects at the crime scene or victims.
medical diagnosis
animal or plant breeding.
IN VITRO/PCR
describe the reaction mixture in the first stage of PCR
- DNA fragment to be amplified
- primers
- free nucleotides
- DNA/ taq polymerase
GENETIC FINGERPRINTING
what are DNA problems and how are they used to locate specific alleles?
short, single stranded pieces of DNA complementary in bases to DNA/gene
They are labelled (e.g. fluorescently labellee) and amplified using PCR.
Then they are mixed with single stranded DNA VNTRs. The probe will bind if the allele is present.
IN VITRO/PCR
name and describe the first stage of PCR?
Denaturation
The temperature is first increased to 95 degrees to break the H bonds and split the DNA into single strands.
IN VITRO/PCR
describe the second stage of PCR.
Annealing
the temperature is decreased to 55degrees so primers can attach (anneal) and is cool enough for H bonds to reform.
IN VITRO/PCR
describe the last stage of PCR.
synthesis
DNA polymerase attaches to complementary free nucleotides and makes a new stands to align next to each template (synthesis).
The temp is increased to 72degrees (optimum temp for taq polymerase)
DNA PROBE
the scientists used a radioactively labelled DNA probe to show the cells contained a gene.
describe how they would do this.
Extract DNA and add restriction endonucleases.
Then separate the fragments using gel electrophoresis.
Treat the DNA to form single strands.
The probe will bind to the gene.
Use autoradiography to show the bound probe.
describe how DNA is broke down into smaller fragments [2]
restriction endonuclease cuts the DNA at a specific base sequence/ at recognition site.
RECOMBINANT DNA
what’s the role of reverse transcriptase?
produces cDNA using mRNA
RECOMBINANT DNA
explain the role of DNA polymerase
joins nucleotides to produce complementary strands of DNA
