Chapter 2.6 Structure of DNA and RNA

Question 1

Transcription

Answer 1

the synthesis of mRNA copied from the DNA base sequences by RNA polymerase

Question 2

Translation

Answer 2

the synthesis of polypeptides on ribosomes

Question 3

Genetic code

Answer 3

according to it, the mRNA determines the amino acid sequence of polypeptides

Question 4

polypeptides

Answer 4

composed of amino acids covalently bonded together in a specific sequence

Question 5

mRNA

Answer 5

messenger RNA, each mRNA is a complementary copy of a DNA gene and has enough genetic information to code for a single polypeptide

Question 6

rRNA

Answer 6

ribosomal RNA, each ribosome is composed of rRNA and ribosomal protein

Question 7

tRNA

Answer 7

transfer RNA, each type of tRNA transfers one of the 20 amino acids to the ribosome for polypeptide formation

Question 8

Translation process

Answer 8

• mRNA will locate a ribosome and align with it, so that the first two codon triplets are within the boundaries of the ribosome
• its tRNA anticodon must be complementary to the first codon triplet of the mRNA molecule. The first amino acid is brought into the translation process –> the identity of the amino acid was determined by the strand of DNA that transcribed the mRNA being translated. While the 1st tRNA sits in the ribosome holding the 1st amino acid, the 2nd tRNA floats in and brings a 2nd amino acid. The 2nd tRNA matches the 3 anticodon bases with the 2nd codon triplet off the mRNA. Two specific amino acids are now being held side by side. An enzyme then catalyses a condensation reaction between the 2 amino acids, and the resulting covalent bond between them is called a peptide bond.
• then the bonds between the 1st tRNA molecule and the amino acid that is transferred in are broken. the 1st tRNA floats away into the cytoplasm and invariably reloads with another amino acid of the same type. The ribosome that has only 1 tRNA in it now moves one codon triplet down the mRNA molecule. This creates room for a third tRNA.
• Final codon triplet will signal stop and the entire polypeptide breaks away from the final tRNA molecule, and becomes a free floating polypeptide in the cytoplasm of the cell

Question 9

Polymerase Chain reaction (PCR)

Answer 9

a means by which DNA replication can be carried out artificially in a laboratory setting. can only replicate short segments of DNA. Scientists can produce huge numbers of these segments to study and analyse. (Crime scene-limited amount of DNA)
-an enzyme is used in PCR that is stable at relatively high temperatures, discovered in 1985 from bacterium cell called Thermus aquaticus (Taq). its enzymes are not denatured at high temperatures, including the specific DNA polymerase that it possesses. This DNA polymerase has been named Taq polymerase.