Topic 8 - The control of gene expression Flashcards
What is a gene mutation?
A change in the base sequence of DNA, which may alter the sequence of amino acids in a polypeptide.
What types of gene mutations exist?
Substitution, addition, deletion, inversion, duplication, and translocation of bases
What is a substitution mutation?
One base is replaced by another, possibly changing one amino acid
What is a frame shift mutation?
Addition or deletion of bases causes a shift in the reading frame, changing every triplet downstream.
Why don’t all substitution mutations change the amino acid?
Due to the degenerate nature of the genetic code, some triplets code for the same amino acid.
What is the potential effect of a mutation on a protein?
It can alter the primary structure, affecting the shape and function of the protein.
What increases the rate of mutation?
Mutagenic agents such as ionising radiation, chemicals like benzene, and viruses.
What are totipotent stem cells?
Cells that can differentiate into any cell type, found in early mammalian embryos
What are pluripotent stem cells?
Found in embryos; can differentiate into most but not all cell types.
What are multipotent and unipotent stem cells?
Found in mature mammals; multipotent form a limited range, unipotent form one type (e.g., cardiomyocytes).
What are iPS cells?
Induced pluripotent stem cells—adult cells reprogrammed to behave like embryonic stem cells.
What is epigenetics?
Heritable changes in gene expression without changes to the DNA base sequence.
What are two main epigenetic mechanisms?
Increased DNA methylation and decreased histone acetylation—both repress transcription
How does oestrogen regulate transcription?
Oestrogen binds to a transcription factor, enabling it to enter the nucleus and activate gene transcription.
What is RNA interference (RNAi)?
A mechanism where siRNA binds to mRNA, preventing its translation
What is the aim of genome projects?
To determine the entire base sequence of an organism’s DNA
Why is proteome determination easier in prokaryotes?
They have fewer regulatory genes and little non-coding DNA.
How can genome knowledge help in medicine?
Identifying antigens for vaccine production and enabling personalised medicine
What is recombinant DNA technology?
Transfer of DNA fragments between organisms using vectors like plasmids.
What are the methods to isolate genes?
Reverse transcriptase to make cDNA, restriction enzymes, and gene machines
How are DNA fragments amplified?
In vitro using PCR; in vivo by inserting into host cells
What are DNA probes used for?
To locate specific genes or alleles via hybridisation.
What is genetic fingerprinting used for?
Identifying individuals and relationships using VNTR patterns.
What ethical issues surround recombinant DNA tech?
Concerns include GM crops, ownership of genetic data, and unforeseen medical risks.
