the 1st unicram (3 part 2) Flashcards
What can mutations be?
Insertion
Deletion
Substitution
Transposition
What are the possible outcomes of insertion or deletion
Causes a frameshift at point of mutation
Produces a stop codon
Produces a non-coding chain
Changes all amino acids, new polypeptide produced
Happens on intron, no effect on the polypeptide produced
What is missense?
A change in one base that changes the amino acid coded for (changes primary structure of the polypeptide being coded for)
What are the possible outcomes of missense?
Different base causes different amino acid, so different primary/tertiary structure. So they can change the functionality
Produces a stop codon, no polypeptide gets produced or a truncated polypeptide gets produced
Happens in non-coding region and has no effect
Tumour suppressor genes?
Control cell cycle at the checkpoints
Cells which rest/are damaged/old move into G0 for destruction
What is proto-oncogenes?
These genes control the production of cell membrane receptors or chemicals that bind to them
Mutation here causes faulty receptors, which turn on without stimulus
Triggers high cell division and the production of cancer
What is epigenetics?
Heritable changes in gene expression
Associated with the relationship of DNA to histones
Changes associated with environmental factors, wether the environment is external or internal
What is the process of epigenetic?
Methylation
Acetylation
Phosphorylation
Ubiquitylation
SUMOlyation
Methylation of histones?
Addition/removal of methyl group (CH3)
Methyl group binds to lysine
Stops negatively charged DNA from binding to the histone, can now be expressed
Methyl group can be removed from lysine, allows DNA to bind and stop gene expression
Methylation of DNA directly?
Methyl group can be added to DNA directly
Catalysed by methyl transferase
Acetylation/Deacetylation?
Acetyl group can be added or removed to histones using enzymes.
Acetylation of lysine reduces positive charge (frees DNA and allows transcription)
Comes from acetyl coA
Deacetylation reverses the process
Effect of phosphorylation on histones?
Makes it more negative, dislodges proteins bound to chromatin or attracts proteins that enhance transcription
What is miRNA?
Enzymes cleave miRNAs to produce a single strand
Base pairs imperfectly with target mRNA to stop translation
What is siRNA?
Small interfering RNA
Repress translation by base-pairing with mRNA to form a double strand
Chromosomal mutations?
When there is an error in the number of chromosomes:
Polysomy and polyploidy
Errors within chromosomes:
Deletion
Duplication
Inversion
Translocation
