Genetic code

Question 1

Gene

Answer 1

A region of the genome that segregates as a single unit during meiosis and gives rise to an identifiable phenotypic characteristic trait

A gene region is a Length of DNA on the genome that contains info for the synthesis of a single protein / peptide chain

Question 2

Genome

Answer 2

Sum of all DNA nucleotide / base sequences in an individual organism

Question 3

2 processes which transfer genetic Info form DNA into peptides

Answer 3

1 transcription - Synthesis of an mRNA strand of nucleotides from a single strand of DNA in a gene region

2 translation - genetic info coded on mRNA is used as a template and converted into a sequence of amino acids

Question 4

Regions found on the genome

Answer 4

1 gene regions which synthesize proteins

2 gene regions which synthesize RNA

3 non-coding regions

4 multiple repeat sequences

5 control regions

Question 5

Codon

Answer 5

• a sequence of 3 nucleotides bases on a mRNA strand which code for a single amino acid
• basis of triplet code

Question 6

Evidence of triplet code

Answer 6

• mutations caused by proflavine in fruit flies
• net effect is to insert addition of delete a base from a stand of DNA
• insertion of deletion would make sequence at right of mutation to be misread leading to defective enzyme or protein

Question 7

Deciphering the triplet code

Answer 7

Ribosome binding ( Leder and Nirenberg )

• makes use of a single strand of synthetic codon , ribosomes and tRNA with their amino acids radioactivity labeled
• filter mixtures on a milipore filter made of cellulose nitrate
• test filter for radioactivity
• if present then codon caused tRNA to bind to ribosome and not go through filter

Question 8

Start and Stop codons

Answer 8

-start codon ( methionine ) is always found at the start of a polypeptide chain ( AUG )

-stop codons dont code for any protein and when on ribosome no tRNA will add amino acids and peptide is released
( UAA UAG UGA )

Question 9

Features of genetic code

Answer 9

1 sequential ( read in a strict way from one end to another )

2 degenerate ( many amino acids can be coded by more than one codon or many tRNA’s can make a single amino acid )

3 universal or ubiquitous ( same codons make same proteins in all organisms although exceptions have been found )

4 unambiguous - a single codon will always code the same amino acids

5. No overlapping and comma less ( code written with no commas and does not overlap )