Lecture 18 - Organisation of the Human Genome 3 Flashcards
What is annotation
Once the human genome had been sequenced, the next step was to identify the genes present.
What is the presence of a protein coding gene indicated by
Open Reading Frame (ORF)
What could inter-species sequence comparison be used for
To further suggest that detected ORF represented a true protein coding gene
What are ESTs and what do they do
Expressed Sequence Tags
How many protein coding genes are in the human genome
22,000
What are TEs
Transposon Elements
What are a large number of protein-coding genes encoding for
rRNAs, tRNAs, snRNAs
What are long non-coding RNAs (lncRNAs)
Thousands of these exist and the size of them varies
Some have been shown to play important roles in regulating gene transcription by interacting with DNA
The function of the majority of them though has not been characterised
Their sequence is poorly conserved between species
What are miRNAs
MicroRNAs
These are tiny RNAs (~22nt) that bind to the 3’UTR of mRNAs in order to regulate their translation
miRNAs are highly conserved
We’re still discovering new ones
Tens of thousands probably exist
What are TEs (full def)
A large proportion of the genome is made up of highly repetitive transposon-based genes
These transposable elements or ‘TEs’ can change their position and multiply within the genome
The biological role of TEs is still unclear, but it’s thought they may have a role in promoting genome evolution by regulating genome complexity
What are the 4 classes of TE
LINEs
SINEs
LTRs
DNA Transposons
What do retrotransposons do
Amplify
What are LINEs
Long Interspersed Nuclear Elements (LINEs) are a very common type of retroptransposon
Three families exist, LINE-1, LINE-2 and LINE-3
LINE-1 genes are by far the most common
What does a LINE1 gene consist of
They consist of mini-systems that encode enzymes capable of copying and pasting the gene itself and hence they can function as autonomous units
What are LTRs and ERVs
Long Terminal Repeats (LTRs) are usually associated with endogenous retroviral (ERV) sequences
These derive from retroviral sequences which have become non-infectious, but have maintained transposon activity
At some point in our history they infected the germline and have thus been transmitted through the population
