Replication, Transcription and Translation

Question 1

DNA Replication

Answer 1

1. The double helix is unwound by a helicase and topoisomerase
2. One DNA polymerase produces the leading strand copy
3. Another binds to the lagging strand. This enzyme makes discontinuous segments (called Okazaki fragments)
4. DNA ligase joins them together

Question 2

what is trascription ?

Answer 2

the process of synthesising an RNA transcript with the transfer of sequenece information from a DNA template

Question 3

what is the DNA molecule trabsribed into ?

Answer 3

a complementary sequence of bases called mRNA which are used for protein synthesis

Question 4

what is the DNA molecule trabsribed into ?

Answer 4

a complementary sequence of bases called mRNA which are used for protein synthesis

Question 5

how is mRNA synthesised ?

Answer 5

• from DNA during transcription and forns a single nucleic acid chain

Question 6

what pattern doe mRNA carry ?

Answer 6

• 3 nucleotide sequences which form codons that specify to the amino acid sequenece for protein sythesis

Question 7

what is tRNA?

Answer 7

• key molecule that deciphers the 3 nucleotides codons of mRNA in protein synthesis
• tRNA has an antoi codon which which recorgnises the codon on mRNA to bring about protein synthesis

Question 8

what does rRNA do in protein systhesis ?

Answer 8

• associates with a range of protein to form the small and large sub-units of ribososmes
• provide spatial and complementary structure to move along mRNA to bind to tRNA

Question 9

what are the main 2 steps in protein systhesis ?

Answer 9

1. transcription
2. translation

Question 10

what are the 3 stages of transcription ?

Answer 10

1. Initiation
2. Elongation
3. Termination

Question 11

what happens in the stage of initiation ?

Answer 11

• RNA polymerase (RNAP) + general trancription factors bind to promoter DNA
• RNAP creates a transcription bubble: separation of 2 strands of DNA by breaking hydrogen bonds between nucleotides

Question 12

what are the 6 general transcription factors ?

Answer 12

1. TFIIA
2. TFIIB
3. TFIID
4. TFIIE
5. TFIIF
6. TFIIH

Question 13

What is the RNA polymerase-promoter closed complex referred to as ?

Answer 13

preinitiation complex

Question 14

what happens in the stage of elengating ?

Answer 14

• RNAP adds RNA nucleotides given that athey are complimentary
• RNA sugar-phosphate backbone forms with assistance from RNAP to form an RNA strand
• Proofreading mechanism for any errors

Question 15

what happens in the stage of elengating ?

Answer 15

• RNAP adds RNA nucleotides given that athey are complimentary
• RNA sugar-phosphate backbone forms with assistance from RNAP to form an RNA strand
• Proofreading mechanism for any errors

Question 16

What happens in the stage of termination ?

Answer 16

1. hydrogen bonds in RNA-DNA helix break = newly synthesized RNA strand
2. RNA is further processed
3. RNA may exit cytoplasm through nuclear pore complex

Question 17

what happen is Translation ?

Answer 17

mRAN is translated into protein

Question 17

what happen is Translation ?

Answer 17

mRAN is translated into protein

Question 18

what does each ribosome have ?

Answer 18

1. Binding site for mRNA
2. Three binding sites for tRNA ( A +P : charged tRNA bind during peptide synthesis, E : discharged tRNA)

Question 19

what are the 3 stages of translation ?

Answer 19

1. Initiation
2. Elongation
3. Termination

Question 20

what happens in the initiation stage of translation ?

Answer 20

1. initisted by Met-tRNAi coded by AUG near a 5’start codon
2. 40S subunit with Met-tRNAi : 5’cap and scans mRNA start codon

Question 21

what are Eukaryotic Initiation Factors (eIF) ?

Answer 21

interact with the 40S ribosomal subunit to stimulate assembly of the translation initiation complex

Question 21

what are Eukaryotic Initiation Factors (eIF) ?

Answer 21

interact with the 40S ribosomal subunit to stimulate assembly of the translation initiation complex

Question 22

what happens in the termination stage of translation ?

Answer 22

1. Stop codons triggering release of the completed polypeptide chain UAG,UAA,UGA
2. No tRNA exists for the stop codon
3. Requires specific protein: releasing factor (eRF)