Transcription and Translation

Question 1

Transcription Def.

Answer 1

Copying DNA to make mRNA

Question 2

Translation Def.

Answer 2

Converts mRNA into protein

Question 3

RNA Outline

Answer 3

Long unbranched sigle strand chain of ribonucleotides joined by 3’ to 5’ phosphodiester bonds. 3 Types: messenger, ribosomal, transfer

Question 4

Transcription Outline

Answer 4

Catalyzed by RNA polymerase (no primer) Transcribes a DNA strand reading 3’ to 5’ and creating RNA 5’ to 3’. Gene contains distinct promoter (start) and terminator (end) sequences

Question 5

Untranslated Regions (UTR)

Answer 5

Part of mRNA that doesn’t code for protein but provides information for translation process

Question 6

Coding Strand (sense) (Def.)

Answer 6

DNA strand that mRNA is identical to (barring Uracil)

Question 7

Template (antisense) Strand (def.)

Answer 7

DNA strand that RNA polymerase uses to form mRNA

Question 8

Gene Orientations on DNA strands

Answer 8

Are opposite to each other

Question 9

Translation Bubble Outline

Answer 9

How RNA Polymerase moves along DNA

Question 10

Polydenation Signal

Answer 10

Sequences of bases that act as terminator sequence for transcription

Question 11

Components of Complex (Eukaryotic) Transcription

Answer 11

Activators, repressors, basal transcription factors, Coactivatord

Question 12

Activators Def.

Answer 12

Proteins that bind to enhancer genes. Speeding up transcription rate

Question 13

Repressor Def.

Answer 13

Proteins bind to silencer genes . Slow transcription

Question 14

Coactivators Def.

Answer 14

Adapter molecules. Integrate signals from activators and repressors

Question 15

Basal Transcription Factors Def.

Answer 15

When stimulated by activators they begin transcription by placing RNA at start sequence

Question 16

Why Eukaryotic Transcription is more complex

Answer 16

More genes, more non-coding DNA and differentiated/ selective expression

Question 17

Heterogenous Nuclear RNA (hnRNA)

Answer 17

RNA molecules synthesised RNA polymerase 2 calles primary transcripts

Question 18

Post-Transcriptional mRNA Processing Modification

Answer 18

hnRNA modified 5’ Capping, splicing and 3’ poly(A) tailing

Question 19

mRNA precursors 5’ Capping Outline

Answer 19

7-methyl-guanosine residue addition, 5’-5’ triphosphate link to 5’ mRNA, guanyltransferase (capping enzyme) catalyses. Cap binds sets of proteins

Question 20

5’ Capping Functions

Answer 20

Protect 5’ end from nuclease, guides mRNA through nuclear pore and permits translation initiation

Question 21

3’ poly(A) tailing mRNA precursors

Answer 21

After polyadenylation signal, endonuclease recruitment and mRNA cleaved poly(A) polymerase adds 40-250 A residues to cleaved (3’) end. Tail shortens after entering cytosol.

Question 22

Poly(A) Polymerase Functions

Answer 22

Stabilises mRNA molecules, slows 3’ -exonucleases (enzymes cleave nucleotides) and facilitates mRNA nucleus exit

Question 23

mRNA precursor splicing outline

Answer 23

Necessary for eukaryotes because of genes in different regions in mature mRNA. Non-coding sequences (introns) are cut out. Small nuclear ribonucleoproteins (snRNPs) form spliceossome which atacks 5’ intron end. 5’ becomes attached to A nucleotide forming DNA loop. Free 3’ end attacks 5’ end of other. 3’ and 5’ ends bond covalently

Question 24

Relationship between protein mRNA codes for and splicing

Answer 24

mRNA that code for different proteins have different genes kept/cut

Question 25

Open Reading Frame (Def.)

Answer 25

Set of codons that run continuously bound by initiation and termination codons

Question 26

Codon Def.

Answer 26

3 nucleotides which code for amino acid

Question 27

Codon Notation

Answer 27

5’ base - Middle Base - 3’ base

Question 28

Synonymous (silent) Genetic Mutation

Answer 28

Produces same amino acid

Question 29

Nonsynonymous (missense) Gene Mutation

Answer 29

Produces different amino acid

Question 30

Nonsense (stop) Gene Mutation

Answer 30

Stop codon added

Question 31

Genetic Code Characteristics

Answer 31

Specific, universal (across species), redundancy (several codons code same amino acid), non-overlapping (strict sequence)

Question 32

tRNA Structure

Answer 32

Cloverleaf shape. Amino acid binds to acceptor arm if tRNA molecule is complementary (Aminoacyl-tRNA-synthetases). Anticodon arm binds with mRNA

Question 33

Wobble Base Pairing

Answer 33

Pairings between tRNA and matching codons are flexible (not perfectly aligned). Some tRNAs match more then 1 codon, single tRNA can recognise 2 codons. Increases tRNA efficency

Question 34

Translation Initiation Outline

Answer 34

2 Parts. Components of chain formation assembly and recoginition of tRNA(met) molecule

Question 35

Chain Formation Components assembly

Answer 35

2 ribosomal sub units (40S and 60S), mRNA, complementary tRNA (1st mRNA codon) Guanosine Triphosphate (GTP), initiation factors

Question 36

Key Ribosome Sites

Answer 36

Aminoacyl Site (tRNA acceptor), peptidyl site (amino acid chain), exit site (deacylated tRNA)

Question 37

Elongation Outline

Answer 37

Ribosome translates mRNA in 5’ to 3’ direction. Aminoacyl-tRNA delivered to Aminoacyl site via elongation factors. Peptide bonds form between aa by peptidetransferase. Growing aa chain moves to A site. Ribosome bond is translocated 3 nucleotides in 3’ direction (next codon)

Question 38

Termination Outline

Answer 38

Occurs when 1 of 3 termination codons in A site (release factor signalled). Release binds to A site. New protein released. Disassembly of tRNA-ribososme-mRNA complex