Intervening Sequences - Introns - Genetics

?
  • Created by: Alex
  • Created on: 13-04-13 13:00
Introns
Non-coding sequences in the Gene that do not appear in the mature mRNA as they are removed by splicing
1 of 29
Occurence
Variable could be 0,1,2 or 20
2 of 29
Size
Variable from 70-80 nucleotides to several thousands - smaller more common
3 of 29
What percent of the human genome are introns
24%
4 of 29
What percent of the human genom are exons
1%
5 of 29
What makes up the rest of the genome
DNA between genes - often highly repeated sequences of DNA
6 of 29
Self -splicing introns
Some introns have enxymatics activity that allows them to self splice and therefore cut themselves out of the RNA
7 of 29
Introns in nucleus of eukaryotes - splicing
Require a spliceosomw to remove introns and join extrons
8 of 29
Spliceosome
removes introns from a transcribed pre-mRNA (hnRNA) segmen. Complec of several protiens and RNA molecules - resembles a ribosome
9 of 29
Sequence of a intron
Starts wiht gT, ends with AT. Sequences next to gT and AT as well as the brand point sequence in the middle are all similar
10 of 29
Functions of introns
Some contain control sequences(rare), depending on how slices one RNA can be sliced to produced many different mature mRNAs. involcved in evolution - allowed genes encoding new and large proteins to be easily produced by recombination of existing one
11 of 29
Average numan gene length
27,000 nucleotides
12 of 29
Average number of exons
9
13 of 29
Average length of a human exon
145 nucleotides
14 of 29
average human intron length
3365 nucleotides
15 of 29
What makes up the rest of the human genome
the rest is the DNA between genes – often highly repeated short sequences of DNA
16 of 29
Intron Sequence
sequences next to the GT and the AG and also a third sequence in the middle (called the branch point) are all similar in each intron (they are consensus sequences). The branch point is a fixed distance from the 3´ end
17 of 29
spliceosome
A spliceosome is a complex of specialized RNA and protein subunits that removes introns from a transcribed pre-mRNA (hnRNA) segment
18 of 29
Intron splicing
1. Spliceosome cuts 5´ boundary 2. 5´ boundary of intron is joined to branch point 3.3´ boundary is cut, exons are joined and lariat is released
19 of 29
Lariat (intron)
Lasso shaped intron (loop with long 'rope end') - shape spliced intron is released as
20 of 29
Alternative Splicing
Constitutive splicing, Exon skipping, Intron Retention, Mutually exclusive Exons, Alternative 5' and 3' splice site
21 of 29
Constitutive splicing
Every Intron is cut out at every intro/exon meet point leaving the full unchanged exons behind
22 of 29
Intron Retention
when introns are not spliced out of the RNA transcript, resulting in the intron(s) being retained within the mRNA as part of an exon
23 of 29
Exon skipping
cells to “skip” over faulty or misaligned sections of genetic code, leading to a truncated but still functional protein despite the genetic mutation. restore the reading frame within a gene
24 of 29
Mutually exclusive exons
Refer to a case in which multiple cassette exons are used in a mutually exclusive manner. In the simplest case: two consecutive exons that are never both included in the mature mRNA transcript.
25 of 29
Alternative 3'/5' splice site
inclusion or skipping of the extended part of the exon, Cut's of the 3' or 5' end of the exon along side the introns
26 of 29
Why do introns exist?
important way in which the cell can encode many related proteins with one gene. decided by protein factors that bind to the intron boundaries and either help or hinder cutting by the spliceosome
27 of 29
Domain (in protein)
conserved part of a given protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain
28 of 29
Introns and protein domains
Thought introns are at the point a gene encodes a junction between a domain - haemoglobin and Leghaemoglobin support
29 of 29

Other cards in this set

Card 2

Front

Occurence

Back

Variable could be 0,1,2 or 20

Card 3

Front

Size

Back

Preview of the front of card 3

Card 4

Front

What percent of the human genome are introns

Back

Preview of the front of card 4

Card 5

Front

What percent of the human genom are exons

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »