Topic 8 Mutations Flashcards
What is a mutation
Change in the DNA base sequence
What are the 6 types of gene mutations
- Addition
- Deletion
- Substitution
- Inversion
- Duplication
- Translocation of bases
What is addition mutation
One extra base is added
Results in frame shift so all the codons are now different
What is the deletion mutation
The deletion of a base sequence frame shift backwards
What is a substitution mutation
Where one base is swapped for another this could result in different amino acid or the same as genetic code is degenerate
What is inversion mutation
Section of bases when they re join they are inverted so this section of code is read backwards
What is duplication
Where one base is duplicated at least once also causes frame shift
What is translocation
Where a section of bases on one chromosome detaches and attached onto a different chromosome
What are stem cells
Undifferentiated cells that can continuously divide and become specialised
What are the 4 different types of stem cells
Totipotent, pluripotent, multipotent and unipotent
What is a totipotent stem cell
Divide and produce any type of body cell for a limited time in early embryos
What are pluripotent stem cells
Found in embryos can divide into unlimited numbers and be used in treating human disorders can turn into everything except placenta cells
What are multipotent and unipotent stem cells
Found in nature mammals and can divide to form limited number of different cells
What are induced pluripotent stem cells
(IPS) can be produced from adult somatic cells using appropriate protein transcription factors to overcome ethical issues
Genes that were switched off to make the cell specialised must be switched back on done using transcriptional factors
How is transcription controlled
In eukaryotes transcription of target genes stimulated or inhibited when specific transcriptional factored move from cytoplasm into nucleus
Can turn genes on or off
How does transcription factors occur (4)
- Transcription of gene occurs when molecule from cytoplasm enters nucleus binds to DNA
- These are proteins called transcription factors each binds to different base sequence on DNA and initiate transcription of genes
- Once bound transcription begins creating mRNA for the gene which is then translated in the cytoplasm to create protein
- Without binding transcription factors gene is inactive and protein won’t be made
What is oestrogen
A steroid hormone that can initiate transcription
What is epigenetics
Heritable change in gene function without changing the DNA base sequence caused by changes in environment
What is methylation of DNA
When methyl groups are added to DNA attach to base cytosine
Prevents transcription factors from binding and attracts proteins that condense the DNA histone complex so prevents a section of DNA from being transcribed
What is acetylation of his tone proteins
Decreased acetylation of associated histones inhibits DNA transcription
If acetyl group removed from histones become more positive and attract phosphate group on DNA
Makes DNA and histones more strongly associated and hard for transcription factors to bind
What is RNAi
RNA interference this inhibits translation
What is the molecule that destroys mRNA
siRNA (small interfering RNA)
How does siRNA work
An enzyme can cut the mRNA into siRNA
One strand-of the siRNA combines with another enzyme
This siRNA enzyme complex will bind via complementary base pairing to another mRNA molecule once bound enzyme with cut up mRNA so it can’t be translated
How does cancer form
Mutation of genes and non functioning proteins or if mitosis is not regulated resulting in uncontrollable division
What is a benign tumour
Grow large at a slow rate
Non cancerous
Produce adhesive sticky molecule so it can’t move
Impact is localised
Non life threatening normally
What is a malignant tumour
Cancerous
Grow large and rapidly
The tumour can break off and spread to other tissues in body
Not encapsulated
Can reach blood supply
For a tumour to develop what genes would need to have mutated
Tumour suppressor gene and/or the oncogene
What are oncogenes
Mutated versions of protocogenes which creates proteins involved with the initiation of DNA replication
Oncogenes can mutate to cause cells to permanently activated to make cells divide continuously
What are tumour suppressor genes
Produce proteins to slow down cell division and cause cell death
What happens if there is a mutation in tumour suppressor gene
Gene not produced so cell division would continue and mutated cells Wouldn’t be identified
How can oestrogen cause cancer
Once menopause is reached you no longer produce oestrogen from ovaries so instead fat cells in breast tissue produce oestrogen which has been linked with breast cancer
This could be due to oestrogen activating s gene that initiated transcription and if this is a proto oncogene so this grid permanently turned on activation cell division
What are the 3 recombinant DNA technologies
-creating DNA fragments
- genetic fingerprinting
- genetic screening, counselling and locating genes
What is recombinant DNA technology
Combining different organisms DNA which could enable scientists to manipulate and alter genes to improve industrial processes
Explain the process of reverse transcription (6)
- Enzyme makes DNA copies from mRNA this enzyme is revers transcriptase
- A cell that naturally produced lots of the protein of interest
- These cells should have large amounts of mRNA for the protein
- The reverse transcriptase enzyme joins the DNA nucleotides with complementary base pairs to the mRNA sequence
- Single sensed DNA made
- To make DNA double stranded DNA polymerase used
What are restriction endonucleases
Anyone’s that cut up DNA
What is a promoter region
Sequence if DNA which is the binding site for RNA polymerase
How do you insert DNA into a vector
Plasmid is cut open using restriction endonucleases
This creates sticky ends so DNA fragment sticky ends are complementary to the sticky ends of plasmid
What are the 3 different marker genes that can be used to identify bacteria
- Antibiotic resistance
- Genes coding for fluorescent proteins
- Evened coding for enzymes
How do the fluorescent markers work
Jellyfish contain glowing gene this gene can be inserted into bacteria plasmid
What is in vitro fertilisation
Fragments of DNA can be amplified in vitro via the polymer as e chain reaction
What is the method of PCR(3)
- Temperature is increased to 95° to break down hydrogen bonds and split DNA into single strands
- Temperature decreases so that primers can attach (annealing)
- Enzyme DNA polymerase attaches to complementary free nucleotides and makes new strand to align next to each template
Temperature increases to the optimum for taq polymerase
Give 3 advantages of PCR
- Automated - efficient
- Rapid - 100 billion copies of DNA made in hours
- Doesn’t require living cells
What are DNA probes
Shirt single stranded pieces of DNA labelled radioactively or fluorescent ly so you can locate specific alleles see if they contain gene of interest
What are VNTRS
variable number of tandem repeats
What are VNTRS used for
Analysis of DNA fragments used to determine genetic relationships
What is gel electrophoresis
Agar gel creates resistance for moving DNA and smaller pieces of DNA can move faster
This shows the lengths of VNTRS separates
What is hybridisation
DNA probes added and they will mix with the single stranded VNTRS and bind to them
