Protein Synthesis

Outline the purpose of transcription and each step of this process

Transcription is the process of using the DNA template to create a strand of mRNA . Transcription has three stages: initiation, elongation, and termination.

Describe the role of RNA polymerase in transcription 

RNA polymerase catalyzes transcription by unwinding DNA and forming covalent bonds between mRNA nucleotides.

Explain the role of hydrogen bonding and complementary base pairing in transcription, emphasizing the pairing of adenine (A) on the DNA template strand with uracil (U) on the RNA strand

During transcription, RNA nucleotides form complementary base pairs with DNA nucleotides of the gene being transcribed. The DNA and RNA bases are held together by hydrogen bonds.

Explain the significance using single DNA strands as a template for transcribing a base without changing the DNA base sequence particularly in somatic cells that do not divide.

Single DNA strands can be used as a template for transcribing a base sequence, without the DNA base sequence changing. In somatic cells that do not divide, such sequences must be conserved throughout the life of a cell.

Describe how transcription is required as the first step of gene expression that can be switched on and off to regulate which genes are expressed in a cell and which are not at any given time.

Not all genes in a cell are expressed at any given time. Gene expression can be switched on and off by regulating transcription of genes. If transcription does not occur, then translation cannot occur.

Outline the purpose of translation and each step of this process to synthesize polypeptides from mRNA

Translation is the synthesis of polypeptides by ribosome and it occur at the ribosome where the triplet code in mRNA is read to add amino acid to make a polypeptide (one amino acid at a time)

Outline the roles of mRNA, ribosomes, and tRNA in translation

Ribosomes require messenger RNA (mRNA) and transfer RNA (tRNA) to synthesize polypeptides.

mRNA: brings the genetic code from the DNA in the nucleus to the ribosome

tRNA: brings amino acids from the cytoplasm to the ribosome.

Describe the complementary base pairing between tRNA (at an anticodon) and mRNA (at a codon)

During translation, codons of mRNA bind to anticodons of tRNA, within ribosomes, by complementary base pairing. Codons and anticodons form hydrogen bonds between complementary nucleotides. Both mRNA and tRNA contain uracil, so the complementary base pairs are: Cytosine - Guanine, Adenine - Uracil. 

Outline the feature of the genetic code and the reasons for a triplet code in a codon, focusing on “degeneracy” and “universality”

The genetic code is universal, as the same code is used in all life forms. The genetic code is degenerate, as more than one codon may code for the same amino acid. 

Deduce the sequence of amino acids coded by an mRNA strand using the genetic code expressed as a table of mRNA codons

The sequence of amino acids in a polypeptide can be determined using the codon sequences in mRNA, combined with a table of mRNA codons. 

Describe the stepwise movement of the ribosome along mRNA and linkage of amino acids by peptide bonding to the growing polypeptide chain, focusing on elongation of the polypeptide, rather than on initiation and termination

During the elongation phase of protein synthesis, the ribosome moves along the mRNA strand, and amino acids are linked together by peptide bonds to form the growing polypeptide chain.