[Unit 4.2] DNA and Protein Synthesis

Question 1

why cant DNA leave the cell

Answer 1

it is too large
it would risk being damaged by enzymes

Question 2

what are the stages of transcription

Answer 2

start of each gene marked by promoter region. RNA polymerase binds here
Section of DNA unzips (H bonds break)
Free nucleotides line up to complementary bases on anti-sense strand
U replaces T in mRNA
RNA polymerase joins the nucleotides
pre mRNA is formed
pre mRNA is modified - introns removed, exons spliced by enzymes
mature mRNA leaves nucleus

Question 3

what are the stages of translation

Answer 3

-mature mRNA moves into cytoplasm through nuclear pore and into ribosome
-mRNA read by ribosome in codons
-anticodon of complementary tRNA and codon of mRNA form base pairs
-ATP is used in joining amino acids in condensation polymerisation
-amino acids joined by peptide bonds
-sequence of codons determines sequence of amino acids in polypeptide.

Question 4

what are the features of genetic code

Answer 4

universal
degenerate
non overlapping
read in same direction
start code is ATG
multiple stop codes

Question 5

what is meant by saying genetic code is “universal”

Answer 5

all living organisms share the same bases

Question 6

what is meant by saying the genetic code is “degenerate”

Answer 6

one amino acid can be coded for by more than one triplet

Question 7

what is meant by saying the genetic code is “non-overlapping”

Answer 7

triplets are all sequential. it matters where you start. triplets dont share bases