Gene Expression - Stem Cells Flashcards
Gene
Stretch of DNA that codes for a protein
How does mRNA become translated into a protein
1) Codons (3 nucleotides)
2) Codons are complementary to specific tRNA’s
3) tRNA attaches to teh codon thats complementary
4) tRNA delivers a specific amino acid
5) Ribosome joining together the amino acids
6) Forming a peptide bond between each nucleotide
What do we do because we cant use embryonic stem cells or adult stem cells
IPSC’s
Induced pluripotent stem cells
Make adult stem cell totipotent again
Epigenetics
How does the environment influence our DNA
How does epigenetics affect histomes
Whether they are wrapped or not
What changes how histomes are wrapped
Wrapped = methylation attaches onto histome
Unwrapped = acetylation
Whats a gene mutatin
Change in sequence if base pairs in a DNA molecule that may result in an altered plypeptide
Types of mutations
Continously
Spntaneously
What des degenerate mean
Single amin acid may be coded by more than one triplet code
Why might mutations not not alter the polypeptide
Code is degenerate
Codes fro mre than one
What can mutations in DNA base sequences result in
Insertion, Deletion, Substitution of a nucleotide
OR
Inversion, duplication or translocation of a section of a gene
What does an insertion of nucleotides do
Changes original amino acid and creates different triplet of bases
Frame shift
Can change the polypeptides function
Deletion of nuleotides
Nucleotide deleted randomly from DNA sequence mutation
Changes original amino acid, changing the grup of three bases, sometimes frameshift
Changing plypeptides functin
Whats a substitution of nucleotides
Mutation when a base in DNA sequence randomly swapped for a different base
Difference between substitution and insertion and deletion
Substituion only changes amino acid for the triplet in which the mutation occurs, will not have a knock on effect
Three types of substitution mutations
Silent mutations - mutation does nto alter amino aciid sequence, degenerate code
Missense - alters single amino acid in polypeptide, changing single amino acid sequence
Nonsense -mutation creates a premature stop codon, causing plypeptide produced to be incomplete, affecting final protein structure and function
WHats duplication of a gene
Gene or section of gene duplicated so there are two cpies of the gene on the same chromosome
Original version intact = mutation isnt harmful
If second copy is duplicated, can develop new functions
Why are duplication mutations important
Evolutionary change
What is translocation of a gene section
Gene cut in two pieces and attaches to a separate gene
Cut gene is non functioning as it has a section missing
Gene gained the translocation section is also likelly to be non functioning
WHat happenbs if a proto-oncogene is translocated
Boost expression and lead to tumour
What happens ia. Sectionof a tumour suppressor gene is translocated
Faulty tumour suppressor gene
Leads to cell continuoing to replicate when it contains faulty dna
Cuases of mutations
Rate that mutations occur
Exposure to mutagenic agents = high energy ionising radiation (alpha, beta gamma radiation) OR chemicals (NO2, tobacco smoke)
WHat happens as a result of gene mutations on polypeptides
Most mutations do not alter the polypeptide
Small number of mutations alter polyeptide with a different shape
May affect the ability of the protein to perform its funciton
Effect of gene mutations on phenotype
Cellular mechanisms affect phenotype of an organism
Mutation causes major alteration, could affect cellular mechanisms whihc impact the phenotype of an organism
What is potency
Ability of stem cell to differentiate into more than one specialised cell type
Three types of potency
Totipotency
Pluripotency
Multipotency
Describe totipotent stem cells
Produce any type of cell
Embryonic, exist for limited time
During development totipotent cells translate part of their DNA, specialising themselves
Where are pluripotent cells found
Embryos
Differentiate into any type
Not able to differentiate into extra-embryonic cells (placenta cells)
Used to treat disorders
What are induced pluripotent stem cells
Produced from adult somatic cells (that arent gametes) using transcription
Cause genes to be expressed that dedifferentiate a cell back into pluripotent state
What are multipotent adult stem cells
Found in mature mammals
Divide to form a limited number of cell types
Growth, cell replacement, tissue repair
Bone marrow cells
What are unipotent cells
Differentiate into their own lineage
How can diabetes be treated using stem cells
Stem cells differentiated into insulin
Producing pancreatic cells
Benefits of uding stem cells
Treat diseases (diabettes, paralysis)
Organs developed from own patients stem cells, reduces risk of organ rejection and need to wait for an organ donation
Adult stem cells already been used and are successful, proof of benefits
Risk of using stem cells
Cultures in lab could become infected with a virus which could be transmitted to the patient
Risk of stem cells accumulating mutations that can lead to cancer cells
Low numbers of stem cell donors
Social issues
Possible to collect embryonic from birth or after birth (umbilical cord, amniotic fluid)
Lack of peer reviewed clinical evidence of success of stem cell treatments
Educating public about what stem cells can and cannot be used for
Ethical issues
Stem cells from embryos, is it right
Create embryos and then destroy them, who owns them
Should an embryo be treated as a person with human rights
Methd creating tissue cultures
1) Disinfect surfaces and soak apparatus in sterilant = no fungi contaminate
2) break small floret of cauliflower from plant
3) sterilise explant by soaking in steriliser and swirl
4) take out explant and add to container of agar growth medium (get nutrients
5) leave container holding agar growth medium
