Topic 4 Protein Syntheis

Question 1

What is the definition of a gene?

Answer 1

Base sequence of DNA which codes for a specific amino acid sequence of a polypeptide and functional RNA.

Question 2

What is a locus?

Answer 2

Fixed poison on a DNA molecule.

Question 3

Describe prokaryotic DNA
What organelles in plant and eukaryotes have prokaryotic DNA?

Answer 3

Short circular DNA not associated with histone
Mitochondria and chloroplast have prokaryotic DNA

Question 4

Describe Eukaryotic DNA

Answer 4

Long linear DNA and associated with histones

Question 5

What is the purpose of histones?

Answer 5

Histones condense DNA to form chromosomes

Question 6

What is the definition of Codon

Answer 6

Triplet of bases that encode for a specific amino acid sequence

Question 7

What is the definition of Genome?

Answer 7

Full DNA sequence in a cell

Question 8

What is a proteome?

Answer 8

Full range of proteins that a cell able to produce

Question 9

What are the properties of the genetic code?
What does each property mean?

Answer 9

1:Universal-the code is the same for all organisms

2:Degenerate-more codons than AminoAcids so some AminoAcids code for same codon

3:Non-Overlapping-each base is part of one codon so each base is read as one discrete unit.

Question 10

Describe mRNA structure

Answer 10

Short single stranded linear chain of polynucleotide

Question 11

Describe the structure of tRNA

Answer 11

Single polynucleotide stand with:
A clove shape.

tRNA has an AminoAcid attached to it and
A anticodon which is complementary to mRNA

Question 12

What are the stages in protein Synthesis and what occurs?
Describe protein synthesis in prokaryotes cell

Answer 12

Stages in protein Synthesise: (1)Transcription-DNA to mRNA (to pre-mRNA in prokaryotic cells)
(2)Splicing-pre-mRNA to mRNA (3)Translation-mRNA to protein using tRNA

In prokaryotic cells Just Transcription and Translation as there is no nucleus so DNA is directly made into mRNA.

Splicing only occurs in eukaryotic cells as it has a nucleus.

Question 13

What occurs in Transcription?

Answer 13

1.Enzyme DNA helical ‘unwinds’ the two DNA stands by breaking the hydrogen bonds between complementary base Pairs.
Only one strand acts as a template

2.Free mRNA nucleotides align and pair with complementary bases on template strand.

3.Enzyme RNA polymerase join up the mRNA nucleotides to form pre-mRNA

Question 14

What occurs in splicing?
How does pre-mRNA enters the cytoplasm?

Answer 14

(Splicing-pre mRNA to mRNA)
1.Introns removed
2.Exons attached back together by condensation reaction forming phosphodiester bond

mRNA formed which exits nucleus through pores into cytoplasm.

Question 15

What are introns and what are exons?
And what occurs in splicing?

Answer 15

Introns are non coding piece of DNA
Exons are coding piece of DNA

Introns are removed in splicing and Exons attach

Question 16

In Translation how does tRNA attach/bind to mRNA strand?

Answer 16

mRNA attaches to RIBOSOME. tRNA molecule with AminoAcid attaches to it as tRNA has an anticodon which is complementary to mRNA and comes to the mRNA strand

tRNA attaches to mRNA by the anticodon which the anticodon is complementary to the first codon on the mRNA

Question 17

How does 2nd tRNA molecule attaches to the mRNA strand?
And how does a peptide bond?

Answer 17

2nd tRNA molecule attaches itself to the NEXT codon on the mRNA in same way as they 1st tRNA molecule.

1st tRNA molecule leave AminoAcid when 2nd tRNA molecule come and a condensation reaction take place between the two AminoAcid and a peptide bond formed.

Requires Enzyme RNA polymerase and ATP for this reaction.

Question 18

How is a polypeptide/protein is made in Translation (Protein Synthesis)

Answer 18

Ribosome moves along to the right releasing tRNA molecules allowing other tRNA molecules to bind.

Process repeats until Ribosome reaches stop codon

Polypeptide/Protein made

Question 19

what is a stop codon?

Answer 19

A stop codon signals termination of Translation