4.1 - 4.2 DNA and protein synthesis

Question 1

define gene

Answer 1

a section of DNA in a chromosome coding for one or more polypeptide

Question 2

what is the coding DNA called

Answer 2

exons

Question 3

what is the non-coding NDA called

Answer 3

introns

Question 4

what does degenerate mean

Answer 4

that there is more than one codon for each amino acid

Question 5

what is longer mRNA of tRNA

Answer 5

mRNA is longer

Question 6

define mRNA

Answer 6

Short, single stranded molecules. Found in the cytoplasm and nucleus. it is made during transcription and copied from DNA therefore complementary to the DNA sequence.
groups of three bases are called codons

Question 7

define tRNA

Answer 7

in the cytoplasm amino acids attach to the transfer RNA molecules. Each tRNA is specific for one amino acid. each tRNA molecule has a sequence of three bases called an anticodon. there are complementary to the codons on the mRNA molecule.

tRNA is involved in translation, it carries the amino acids that are used to make proteins to the ribosomes. tRNA is a single polynucleotide strand that is folded into a cover shape. H bonds between basepairs hold the shape.

Question 8

short definition of transcription

Answer 8

where one gene on the DNA is copied into mRNA

Question 9

short definition of translation

Answer 9

where the mRNA joins with a ribosome and corresponding tRNA molecules bring the specific amino acids the codon codes for

Question 10

all transcription (5 steps + splicing)

Answer 10

transcription happens in the nucleus, a complementary RNA of one gene on the DNA is created in the nucleus mRNA is much shorter that DNA so it is able to carry the genetic code to the ribosome in the cytoplasm to enable the protein to be made.

1. the DNA helix unwinds to expose the bases to act as a template
2. only one chain of the DNA acts as a template
3. the unwinding and breaking the hydrogen bonds is catalysed by DNA helicase
4. free mRNA nucleotides in the nucleus align opposite to the exposed complementary DNA bases
5. the enzyme RNA polymerase bonds together the RNA nucleotides to create a new RNA polymer chain, one entire gene is copied.

following transcription pre-mRNA has to be modified to become mRNA that is ready to live the nucleus and take part in translation.
the intros are spliced out by a protein called spliceosome, this leaves behind the exons (only the coding regions)

Question 11

5 steps of translation

Answer 11

1. once the modified mRNA has left the nucleus it attaches to a ribosome at the start codon
2. the tRNA molecule with the complementary anticodon to the start codon aligns opposite the mRNA, held in place by the ribosome
3. the ribosome will move along the mRNA molecule to enable another complementary tRNA to attach to the next codon on the mRNA
4. the two amino acids that have been delivered by the tRNA molecules are joined by a peptide bond. this is catalysed by an enzyme and requires ATP
5. this continues until the ribosome reaches the stop codon at the end of the mRNA molecule. the stop codon does not code for an amino acid and therefore the ribosome detaches and translation ends.