protein synthesis

Question 1

describe transcription

Answer 1

DNA separates into 2 strands
breaking hydrogen bonds
by DNA helicase
free RNA nucleotides align
by complementary base pairing e.g. uracil replaces thymine
RNA polymerase joins nucleotides
mRNA is modified
introns removed (splicing)
mRNA detaches and moves out of nucleus

Question 2

describe translation

Answer 2

modified mRNA moves to ribosome
tRNA carries specific amino acid
mRNA read in codons
complementary anticodon of tRNA attaches to start codon of mRNA
ATP used in joining amino acids
amino acids joined by peptide bonds
tRNA used repeatedly until stop codon
ribosome detaches

Question 3

explain why genetic code is described as non-overlapping and degenerate

Answer 3

each base is part of only one codon
some amino acids are coded for by more than one codon/base sequence

Question 4

compare tRNA and mRNA

Answer 4

tRNA-
clover shaped
amino acid binding site
anticodon
has H bonds between complementary base pairs

mRNA-
linear
no H bonding
no base pairs

Question 5

role of tRNA in process of translation

Answer 5

anticodon complementary to codon reads message on mRNA
specific amino acid is carried to ribosome
to form the correct sequence of amino acids along polypeptide

Question 6

comparison of DNA replication and translation

Answer 6

similarities-
H bonds break and DNA unzips
DNA acts as a template for complimentary base
polymerase enzymes are involved

differences-
U replaces T in RNA
in replication, all the DNA is copied, in translation, sections are copied
only one strand is used as a template in transcription, both are used in replication
RNA vs DNA polymerase
mRNA produced vs DNA produced

Question 7

locus definition

Answer 7

position of a gene on a strand of DNA

Question 8

gene definition

Answer 8

short sections of DNA that code for a protein

Question 9

mutation definition

Answer 9

change in the base sequence of a gene

Question 10

allele definition

Answer 10

alternative forms of a gene

Question 11

codon definition

Answer 11

sequence of three bases called a triplet that code for a specific amino acid. the base sequence determines the amino acid sequence in a polypeptide

Question 12

exon definition

Answer 12

sequence of bases in a gene that code for the polypeptide

Question 13

introns

Answer 13

eukaryotes only!!!!
sequence of bases in a gene that do not code for a polypeptide

Question 14

non-overlapping

Answer 14

each base is part of only one codon

Question 15

degenerate genetic code

Answer 15

there are 20 amino acids and 64 codons, so most amino acids have more than one codon