Section 8 Genes Flashcards
What is a stem cell?
An unspecialised/ undifferentiated cell with a potential to form any cell within the body
How does a stem cell become a specialised cell?
Differentiation
3 changes: Cell shape, number of organelles, new content
Occurs by controlling gene expression
Stem cell in animals/mammals/humans?
Totipotent=zygote
Pluripotent=Embryonic stem cells
Multipotent= bone marrow stem cells
Unipotent= Tissues
What are induced pluripotent stem cells?
Turning unipotent body cells into pluripotent cells involves activating certain deactivated genes using transcription factors
How can stem cells be used in human therapy?
Use stem cells to produce tissues/organs for transplant
Use stem cells to treat irreversible diseases.
Where are the stem cells within a plant cell?
In embryo= Zygote /Embryonic stem cells
In adult= meristem cells in stem/shoot/root
What are stem cells used for in plants?
Traditionally cuttings were taken from plants and used to grow genetically identical plants
Tissue culture
What is the process
Take cutting from plant or root (called an explant)
Place the explant in a nutrient rich medium so meristem cells divide by mitosis
Produces a mass of meristem (called callus)
Take each meristem cell and grow in plant grow factor medium to promote differentiation and formation of shoot and root
transfer plant to soil and greenhouse
Then transfer to field
What is controlling gene expression?
Either activating or inhibiting genes
Activating= protein made
Inhibition gene= protein not made
Examples of activating genes?
Using oestrogen
Oestrogen can enter a cell by simple diffusion and bind to receptors on the transcriptional factor
Causes transcriptional factor to change shape
So transcriptional factor can now enter nucleus and bind to promoters on the DNA to activate transcription
Examples of inhibiting genes?
Using siRNA (small interfering RNA)
Making siRNA= double stranded RNA cut down into small sections, made single stranded, then attaches to an enzyme
siRNA will bind to complementary sections on the mRNA= the enzyme will cut the mRNA so translation cannot occur= gene inhibited (protein not made).
What is epigenetics?
Heritable changes in the gene function without changes to the base sequence of DNA
Changes may be due to lifestyle, stress, diet
Chromatin is surrounded by an epigenome
Epignenome can either cause the chromatin to become more condensed or more loose
Chromatin becoming more condensed means transcription factors cannot reach the DNA and the gene will become inactivated
Chromatin becoming more loose means transcription factors can reach the DNA and the gene will be activated
These changes may be caused by Acetylation or Methylation.
How does methylation and acetylation affect the genome?
Increased methylation= adding methyl groups, this attracts proteins which condense the DNA-histone complex so transcription factors cannot gain access
Decreased acetylation= removing acetyl groups, increases positive charges on the DNA which condense the DNA histone complex so transcription factors cannot gain access (gene inhibited).
What is cancer?
Formation of a malignant tumour
Is caused by uncontrolled cell division (mitosis)
What is gene mutation?
A change in the base sequence of DNA
2 types=substitution and insertion/deletion
Substitution= replace one base for another, changes one triplet code
Insertion=adding a base, deletion= removing a base
Malignant vs benign tumours?
Malignant tumours
Rapid growth (rapidly dividing cells) Cells are unspecialised Cells can spread (Metastatis) Systemic effects Requires surgery/ chemotherapy/ radiotherapy
What normally controls cells division (mitosis)?
2 genes: proto-oncogene & tumour suppressor gene
Both produce proteins to control cell division
Proto-oncogene stimulates cell division
Tumour-suppressor gene inhibits cell division
Proto-oncogene produces growth factor and receptor protein, when the growth factor binds to receptor protein on cells it stimulates DNA replication that leads to cell division
Tumour suppressor gene produces a protein that inhibits cell division
What is cancer? (CONT.)
Caused by mutation of genes that control cell division
Causes of mutation = random or mutagens
Mutation of proto-oncogene leads to formation of a oncogene = over production of growth factor or receptor proteins permanently active= over stimulation of cell division
Mutation of tumour suppressor gene = loss of protein to inhibit cell division
Oestrogen and cancer?
Oestrogen leads to activation of genes- high levels of oestrogen can lead to over activation of proto-oncogen forming an oncogene= cancer
Epigenetics and cancer?
Main example= increased methylation of tumour suppressor genes leads to inhibition of tumour suppressor genes leading to cancer
What is genetic engineering?
Changing the genetic make-up of an organisms DNA by adding or removing a gene
The DNA becomes Recombinant
The organism becomes genetically modified
Why do we genetically engineer animals?
To provide better characteristics
To provide more/ better product
What are some examples of genetically engineering animals?
Additional characteristics
add a gene for disease resistance
Add a gene for growth hormone
Making useful products
Why are plants genetically engineered
To give them additional (favourable) characteristics
So they can make useful products
Examples of genetic engineering in plants?
Additional characteristics
Add gene for disease resistance
Add gene for pest resistance
Add gene to promote growth for a higher yield
MAKING USEFUL PRODUCTS
Why are bacteria genetically engineered?
So they can make useful products
E.G. To make proteins such as Insulin
What are the 5 steps of producing human proteins from genetically engineered bacteria?
- Isolation
- Insertion
- Transformation
- Identification
- Growth/cloning
What is the first step of producing human proteins from genetically engineered bacteria and what is the process?
Isolation
Either by reverse transcriptase or restriction enzyme or gene machine
RT= enzyme found in virus converts RNA to DNA, obtaining mRNA for insulin
RE = enzyme found in bacteria, cuts DNA at certain base sequences (called recognition sites) by breaking bond between sugar and phosphate, can cut straight or staggered, staggered used in GE as it leaves exposed bases called ‘sticky ends’ [cuts staggered at 6 base pair palindromes, were the 6 bases read forward are identical to 6 bases read backward on both strands]
GM = build DNA base sequence from know Amino Acid Sequence of the Protein (uses oligosacchairdes)
end result = Isolated Human Insulin Gene
What is the second step of producing human proteins from genetically engineered bacteria and what is the process?
Insertion
Cut plasmid using the RE from isolation stage
Leaves complementary sticky ends
Join human insulin gene with plasmid via the sticky ends
Use DNA Ligase to join the sugar phosphate to backbone
Recombinant plasmid (carrying human insulin gene)
What is the third step of producing human proteins from genetically engineered bacteria and what is the process?
Mix recombinant plasmid with bacteria
Add Calcium ions and heat shock
Bacteria will become permeable and take up the recombinant plasmid
Genetically modified bacteria
What is the fourth step of producing human proteins from genetically engineered bacteria and what is the process?
identify which of the bacteria have taken up the recombinant plasmid and of these which ones have accepted the new gene (human insulin gene)
step 1 = choose a plasmid that carries an Ampicillin Resistance Gene, so when Ampicillin is added only the bacteria that have taken up the recombinant plasmid will survive (as they will have obtained the ampicillin resistance gene)
step 2 = use gene markers (antibiotic resistant, fluorescent, enzyme) to identify which of the remaining bacteria have accepted the human insulin gene, the human insulin gene will be placed in the middle of these gene markers, if the bacteria accepts the human insulin gene they will reject the gene marker & if the bacteria rejects the human insulin gene they will accept the gene marker
antibiotic resistant = tetracycline resistance gene lost if human insulin gene accepted, so bacteria no longer resistant to tetracycline, add tetracycline by replica plating (on another plate that carries a few of the bacteria from each colony in their same position), the ones that die are the ones that we want, identify on original plate
fluorescent = fluorescent gene lost if human insulin gene accepted, so identify bacteria showing no fluorescence
enzyme = enzyme gene lost if human insulin gene accepted, therefore add colourless substrate, where there is no colour change select those bacteria (as enzyme not made to breakdown colourless substrate for colour change)
end result = Genetically Modified Bacteria
What is the fifth and final step of producing human proteins (insulin) from genetically engineered bacteria and what is the process?
Grow genetically modified bacteria
They will produce the protein
What is PCR?
Its a polymerase chain reaction
It is used to replicate DNA artificially
Step 1: heat to 95c hydrogen bonds break, double strand seperates, left with 2 template strands
Step 2: cool to 55c, primers bind (short single stranded sections of DNA) to start of each template strand, prevents the templates from rejoining and allows the DNA polymerase to bind and build a new strand.
Step 3: Heat to 72c, DNA nucleotides attach to complementary bases, DNA polymerase joins sugar phosphate backbone of new strands
Polymerase chain reaction vs semi conservative replication?
PCR can only replicate short DNA fragments, SCR can replicate whole DNA
PCR use 95oC, SCR uses DNA Helicase
PCR uses primers, SCR does not require primers
In vitro vs in vio method of DNA replication?
In-vitro= PCR
In-vivo= using bacteria to replicate DNA
Benefits of in-VITRO= more rapid, less complex
Benefits of in VIVO= more accurate, less chance of contamination
What is a DNA probe?
A short single stranded section of DNA
Has a specific base sequence so it binds to the complementary genes
Is radioactively/fluorescently labelled
If a gene is present in DNA, DNA probe will bind it and show up be radioactivity
What is genetic screening?
Analyse an individual’s DNA for the presence of a particular gene
Use DNA probes
Obtain individuals DNA, make it single stranded, add the specific DNA probe for the gene to be screened for, if the gene is present the DNA probe will bind, will show up as radioactivity on an x-ray film
What is Genetic Fingerprinting?(LONG 5 stage process)
used to produce a unique ‘fingerprint’ of an individual’s DNA (produces a specific banding pattern)
used in forensics and paternity testing
involves analysing the individual’s introns (non-coding DNA)
introns contain repetitive sequences called variable number tandem repeats (VNTR)
the number and length of the VNTR are unique for each individual organism
involves 5 steps: 1. Extraction, 2. Digestion, 3. Separation, 4. Hybridisation, 5. Development
- Extraction
extracting the individual’s DNA - Digestion
cutting the DNA down into fragments
use Restriction Enzymes that cut just outside the VNTR (leaves the VNTR of the introns) - Separation
separate out the DNA fragments by gel electrophoresis
add alkali to make the separated fragments single stranded
transfer the fragments to a nylon membrane by Southern Blotting
add UV light so the DNA fragments set - Hybridisation
add radioactively labelled DNA Probes complementary to the DNA fragments - Development
add photographic film and take an x-ray to produce the banding pattern picture
What is genetic sequencing
Determining base sequence of a genome
Uses whole genome shotgun (WGS) to cut DNA into smaller sections to be sequenced
Bioinformatics is the science by which the information is collected and analysed
Uses= Supports phlyogenetic classification, identify genes that are related to specific diseases
What is a proteome?
Full set of of proteins produced by a certain genome
