Chapter 7- Gene Sequencing Flashcards
How does gene probing work (DNA-RNA hybridisation)
Gene probes find the unique sequence of nucleotides on DNA using a stretch of complimentary RNA
What is a gene probe
Fluorescently labelled mRNA
What are transcription factors?
Proteins that bind to DNA in the nucleus and affect the process of transcribing genetic material
What is a promoter sequence?
Specific regions of DNA to which transcription factors bind to stimulate transcription
Where are promoter sequences found?
At the ‘5 end of DNA
How do enhancer sequences work?
They change the structure of chromatin, making it more or less open to RNA polymerase, stimulating or preventing transcription
What happens in RNA splicing
Pre-mRNA is converted to mRNA. The introns (non-coding DNA) are removed along with some exons. The remaining exons are joined together by enzyme complex spliceosomes.
Why is RNA splicing important?
It allows more variety in the phenotype than is coded for in the genotype
What is DNA methylation
Addition of -CH3 group to modify the structure of histones to silence genes by changing the arrangement of the DNA molecule
Where does DNA methylation occur?
At the cite of Cytosine next to Guanine.
What is DNA methylation used for?
Used in embryonic development and X chromosome inactivation
What happens in DNA demethylation?
A methyl group is removed so gene becomes active and can be transcribed
What are histones?
Positively charged proteins
How is chromatin formed?
DNA winds around histones
What is Heterochromatin?
Supercoiled chromatin, no genes available for transcription
What is active chromatin
Loose chromatin, uncoiled regions of DNA opens up some genes for transcription
What is histone acetylation
COCH3 group added to lysines, opens up the structure forming active chromatin that allows transcription
What is the effect of remove a actyl group?
Chromatin supercoils into Heterochromatin so no genes are available to be transcribed
What is histone methylation
CH3 group added to lysines. Depending on position on lysines methylation may cause inactivation of DNA or activation
What is histone methylation used for?
Often linked to silencing of one X chromosome in every cell of female mammals
What are epigenetic’s
Changes to the DNA structure. Gene expressions that do not alter the base sequence of the DNA strand
