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Biochemistry

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Purines, Pyrimidines and Nucleic Acid Metabolism

Question
32 out of 59
 

Splicing activity present in (AIIMS May 2009)


A mRNA
B tRNA

C snRNA
D RRNA

Ans. C snRNA

1. Nuclear pre-mRNA splicing is the removal of introns and the joining of exons in mRNA.

img001


Introns - found in most eukaryotic genes; non-coding (usually); can be large;
Exons - coding; can be small
img002

2. The splicing process
Sequences specify where the intron is to be spliced out 5’ splice site; 3’ splice site; branch point These sequences are conserved ie in all introns and exons looked at
img003

3. The Spliceosome

a. the machinery that carries out the splicing reaction

  1. A complex of RNA and Protein
  2. Sub-particles are called snRNPs - each contains an snRNA and several proteins

img004
snRNAs

  1. 5 involved in splicing - U1, U2, U4,U5, U6.
  2. U4&U6 are based paired to each other.
  3. Base pair to nucleotides in pre-mRNA

Proteins. Can be:

a. snRNP Proteins - some specific for each snRNP, some common

b. img005Other splicing proteins (non-snRNP)

c.
img006

4. Alternate splicing

  1. some pre-mRNAs can be spliced in more than one way

img007

  1. gives increased variation in proteins
  2. can be tissue specific eg fibronectin

5. mRNA Transport

  1. processed mRNA exits the nucleus via nuclear pores
  2. 5’ cap important for transport
  3. transport can be regulated

Purines, Pyrimidines and Nucleic Acid Metabolism Flashcard List

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