Mutations and Gene Expression Flashcards

Question

Role of RNA interference with miRNA

Answer 1

In mammals, miRNA isn't fully complementary to the target mRNA so it is less specific and can target many mRNA molecules associates with proteins and binds to target mRNA in the cytoplasm miRNA-protein complex blocks the translation of the target mRNA mRNA then moved into a processing body where its stored or degraded When stored it can be returned and translated later

Answer 2

Acquired mutations Occur in the genes that control the rate of cell division by mitosis Causes uncontrolled cell division Results in tumour that invade and destroy surrounding tissue Two types of gene that control cell division: Tumour suppression gene can be inactivated by a mutation - normally slow cell division by stopping cells dividing or slef-destroying them (apoptosis) - mutation will mean protein is not produced so the cells divide uncontrollably Proto-oncogene can be increased by mutation - called an oncogene - proto-oncogenes stimulate cell division by making proteins that make cells divide - oncogenes cause overactive cell division

Answer 3

Not cancerous Grow slower Covered in fibrous tissues that stops them invading other cells Often harmless Can cause blockages or put pressure on organs

Answer 4

Grow rapidly Invade and destroy surrounding tissue Break off and spread to other parts of body in the bloodstream or lymphatic system

Answer 5

Have irregular shape Nucleus is darker and larger Don't produce all the proteins to function correctly Different antigens on their surface Dont respond to growth regulating processes Divide by mitosis more frequently

Answer 6

Adding a methyl group (-CH3) | Is important in regulating gene expression - can control if a gene is transcribed and translated

Answer 7

Hypermethylation - Tumour suppressor genes become hypermethylated, genes not transcribed, proteins that slow cell division not made, cells divide uncontrollably Hypomethylation - porto-oncogenes act as oncogenes - increasing procession of protein that encourage cell division - cells divide uncontrollably

Answer 8

Increased exposure to oestrogen over a long period of time increases chance of breast cancer Theories why: - Oestrogen stimulate breast cells to divide and replicated - more cell divisions increases chance of mutation - increased chance of malignant tumour - If cells become cancerous, oestrogen helps their rapid replication - Oestrogen can introduce mutations directly to DNA of breast cells, increasing chance of cancer

Answer 9

Genetic - specific inherited allies | Environmental - radiation, lifestyle choice (smoking, alcohol), high-fat diet

Answer 10

In eurkayotes Controls whether a gene is switched on or off Works through attachment or removal of chemical groups (epigenetic marks) to or from DNA or histone proteins Dont alter base sequence Alter how easy it is for enzymes needed for transcription to interact with and transcribe the DNA

Answer 11

Most epiginetic marks on the DNA are removed between generations, some escape the removal process and are passed on to offspring. Offspring can therefore be affected by environmental changes which affected their parents

Answer 12

Methylation of DNA is when a methyl group (an epigenetic mark) is attached to DNA coding for a gene Always attaches at the CpG site, which is where cytosine and guanine bases are next to each other Increased methylation changes the DNA structure so that the transcriptional machinery can't interact with the gene, gene is not expressed

Answer 13

Histones are supercoiled around DNA to form chromatin, makes up chromosomes - can be highly or less condensed Histones can be epigenetically modified by the addition or removal of acetyl groups (epigenetic mark) When acetylated, the chromatin is less condensed. Transcription machinery can access the DNA, gene can be transcribed When Acetyl groups are removed, chromatin becomes highly condensed and DNA can't be transcribed - machinery can't access them Histone deacetylase is the enzyme responsible for removing the acetyl groups

Answer 14

Drugs designed to counteract the changes Increased methylation leads to a gene being switched off, Drugs that stop DNA methylation can be used to treat these diseases - azacitidine in chemotherapy Decreased acetylation of histones leads to genes being switched off. HDAC inhibitor drugs, stops HDAC enzymes so proteins remain acetylated and can be transcribed

Answer 15

Bacteria Don't have much non-coding DNA Easy to determine proteome and therefore identify antigens which can be used in vaccines

Answer 16

transferring a fragment of DNA from one organism to another Possible as genetic code is universal Organisms that contain transferred DNA are known as transgenic organisms

Answer 17

mRNA molecules used as templates to make lots of DNA Reverse transcriptase makes DNA from an RNA template cDNA is produced (complimentary DNA) For example, only two copies of insulin gene, but many mRNA copies, possible to make cDNA from insulin mRNA. mRNA is isolated from cells, mixed from free nucleotides and reverse transcriptase

Answer 18

DNA nucleotide strand are palindromic and are antiparallel Restriction endonucleases cut DNA at palindromic sequences Different Restriction endonucleases cut at different sections due to its active site being complimentary DNA is incubated with specific endonuclease and the DNA fragment is cut via a hydrolysis reaction The cut either leaves sticky ends - can be used to bind (anneal) the DNA fragment to another sticky end DNA fragment with complimentary sequences - or blunt ends

Answer 19

Database includes the information needed to produce the DNA fragment Any sequence can be made Sequence required is designed First nucleotide sequence is fixed to some sort of support Nucleotides added step by step in correct order, adding protecting groups to stop branching Short sections of DNA called oligonucleotides are made and are added up to make longer DNA fragments

Answer 20

Vector: organism used to transfer DNA into a cell Vector DNA cut open using same restriction endonulease that was used to isolate DNA - sticky ends are complimentary DNA and DNA fragment are mixed together with DNA ligase - joins the sticky ends together - ligation Forms recombinant DNA

Answer 21

Vector with recombinant DNA transfer the gene into cells Plasmid vectors: heat shock Bacteriophages: infect the cells Host cell take up the gene and are transformed

Answer 22

Only 5% are transformed - use marker genes Inserted at same time Host cells grown on agar plates. Transformed cells will form a colony. Marker gene can code for antibiotic resistance, so only transformed cells will survive and grow when exposed to antibiotic Marker gene can be fluorescent and visible under UV

Answer 23

To produce protein from transformed cells which are coded for by the DNA fragment, the vector needs a specific promoter and terminator region Promoter regions are DNA base sequences that start RNA polymerase producing mRNA. Terminators stop it.

Answer 24

PCR Reaction mixture: DNA sample, free nucleotides, primers and DNA polymerase Primers are short pieces of DNA that are complementary to the bases at the start of the fragment desired DNA mixture heated to 95C to break hydrogen bonds between strands of DNA Mixture then cooled to 55C so primers can bind/anneal to the strands Reaction mixture heated to 72C so DNA polymerase can work DNA polymerase lines up free DNA nucleotides alongside each template strand Base pairing forms new complementary strands Two new copies of the fragments of DNA are formed every one cycle Cycle starts again at 95C and all four DNA strands are used

Answer 25

Altering the defective genes inside cells that cause disorders If caused by 2 mutated recessive alleles you can add a working dominant allele If caused by a mutated allele you can silence the allele by putting DNA in the middle of the allele so it does not function Both involve inserting a DNA fragment into the person's original DNA Uses vectors to do this Somatic therapy - involves altering alleles in body cells - most affected by disorder - doesn't affect sex cells so offspring can still inherit Germ line therapy - involves altering alleles in the sex cells - offspring will not be affected by disorder - currently illegal

Answer 26

Short strands of DNA. Specific base sequence Will bind (hybridise) to target allele if present in sample Has a label attached so it can be detected - radioactive X-ray or fluorescent

Answer 27

Sample of DNA turned into fragments using restriction endonucleases and separated using electrophoresis DNA fragments are transferred to a nylon membrane and incubated with the fluorescently labelled DNA probe If allele present the DNA probe will hybridise(bind) to it Membrane is then exposed to to UV light and if the gene is present there will be a fluorescent band

Answer 28

Variable Number Tandem Repeats Base sequences that don't code for anything and repeat The number of repeats varies in everyone and can be used for genetic fingerprinting

Answer 29

Sample of DNA from blood, saliva PCR to make many copies that contain VNTRs - primers used to to either side of repeats so the whole repeat is amplified DNA fragments produced have lengths that correspond to the number of repeats Fluorescent tag added so the DNA fragments can viewed under UV light Electrophoresis: DNA mixture placed into well and covered in buffer solution that conducts electricity Electrical current added, DNA is negatively charged so they move toward positive electrode at other end of gel Small DNA fragments move faster and travel further - DNA fragments separate according to size DNA fragments viewed as bands under UV light

Answer 30

``` DNA cut Using restriction enzyme Separates according to mass Transfer to nylon membrane Make single stranded - DNA helices Apply probe Radioactive or fluorescent Reference to VNTRS ```

Answer 31

Heritable changes in gene function | Without changes to the base sequence of DNA