RNA processing and translation

Question 1

Conversion of primary transcript into
mature mRNA

Answer 1

Occurs primarily in eukaryotes

Question 2

Conversion of primary transcript into
mature mRNA localised in

Answer 2

nucleus

Question 2

RNA processing achieves three things:

Answer 2

 Removal of introns
 Addition of a 5’ cap
 Addition of a 3’ tail

Question 3

This signals the mRNA is

Answer 3

ready to move out of the nucleus and
may control its lifespan in the cytoplasm

Question 4

5’ Capping involve the addition of

Answer 4

a methylated-guanosine (7-methyl G) is
linked to the phosphates at the 5’ end of the mRNA.

Question 5

Addition of poly-A tail

Answer 5

at 3’ end of the mRNA

Question 5

5’ Capping is mediated by

Answer 5

guanylyl transferase in the capping enzyme complex

Question 5

Functions of 5’ capping (PST)

Answer 5

• Protects against degradation by ribonucleases and 5’ exonucleases
• Serves as recognition site for ribosomes (initiation factors)
• Transports mRNA from nucleus to cytoplasm

Question 6

what attach poly(A) generated from ATP

Answer 6

Poly(A)polymerase and cleavage &
polyadenylation specificity factor (CPSF)

Question 6

Functions pf poly a tai; EP

Answer 6

i. Ensuring efficient translation of the mRNA
ii. Provide stability of the mRNA during
transportation out of the nucleus.

Question 6

Highly regulated and vital in the creation of stable and mature messenger RNA able

Answer 6

to undergo translation during protein synthesis

Question 6

These modifications (5’ cap and 3’ end) share several functions (fph)

Answer 6

◦ facilitate the export of mRNA to the cytoplasm
◦ protect mRNA from hydrolytic enzymes
◦ help ribosomes attach to the 5’ end

Question 6

Removal of introns involves

Answer 6

a complicated “molecular device” called a
spliceosome that involves protein and RNA (like a ribosome).

Question 7

The 3’ end of a eukaryotic mRNA

Answer 7

is trimmed and cleaved 15-20 nucleotides past AAUAAA

Question 7

Eukaryotic genes often contain intervening sequencings (introns)

Answer 7

that separate the exons and must be removed for proper protein translation to occur.

Question 7

Splicing allows an increase in

Answer 7

the information content of a genome due to
alternative splicing products that produce novel proteins.

Question 7

Performed by

Answer 7

spliceosomes (large RNA-protein complex
made of small nuclear ribonucleoproteins (snRNP)

Question 8

Recognize exon-intron
boundaries and splice exons
together by

Answer 8

transesterification reactions

Question 8

The 5′ splice site at the 5′ (left) end of the intron includes

Answer 8

the consensus sequence GU

Question 8

The 3′ splice site at the 3′ (right) end of the intron includes

Answer 8

the consensus sequence AG.

Question 8

The GU-AG rule describes

Answer 8

the requirement for these constant dinucleotides at the first two and last two positions of introns in pre-mRNAs.

Question 8

Why splice?

Answer 8

more than one mRNA can be made from
the same gene.

Question 8

The same pre-mRNA can be

Answer 8

spliced in three different ways, depending on which exons are kept

Question 9

Pre-mRNAs undergo three steps before translation

Answer 9

5’ Capping, polyadenylation, and splicing.

Question 9

Alternative splicing from the same mRNA using different exons allows

Answer 9

cells to choose the protein they will make

Question 9

a poly-A tail

Answer 9

(a chain of around 200 adenine residues)

Question 10

The Genetic Code

Answer 10

The set of rules used by living cells to translate information encoded within genetic material (DNA or mRNA sequences of nucleotide triplets, or codons) into proteins.

Question 11

▪The sequence of codons in the mRNA

Answer 11

defines the primary structure of the final protein.

Question 12

Three nucleotides in mRNA (a codon)specify

Answer 12

one amino acid in a protein.

Question 13

The Genetic Code Characteristics

Answer 13

The triplet sequence of mRNA that specify
certain amino acid
Degenerate
▪Unambiguous
▪ Non overlapping

Question 14

Translation

Answer 14

s the process by which ribosomes read
the genetic message in the mRNA and produce a protein product according to the message’s
instruction.