Section 4 - Genetic Information, Variation and Relationships Between Organisms

Question 1

What is a Gene?

Answer 1

a gene is a section of DNA that codes for the sequences of amino acids in a polypeptide and functional RNA

Question 2

What is the locus?

Answer 2

The location of the gene on the strand of DNA or chromosome. its called the loci if there are multiple genes.

Question 3

How many different types of amino acids are there?

Answer 3

20 different types

Question 4

What is the triplet code?

Answer 4

The standard version of the genetic code, in which a sequence of three nucleotides on a DNA or RNA molecule codes for a specific amino acid in protein synthesis.

Question 5

Why is the triplet code often described as degenerate?

Answer 5

Because some amino acids are coded for by more than one triplet.

Question 6

What is the benefit of Triplet / genetic code being degenerate?

Answer 6

provides protection against mutations in the DNA sequence, as changes to one or two nucleotides in a codon can still result in the same amino acid being produced.

Question 7

What are the features of the genetic code?

Answer 7

• code is degenerate
• each triplet is read in the same direction 5’ to 3’
• three triplets cause for no amino acids. these are called stop codons. they signify the end of a gene
• the genetic code is non overlapping and each base can only be read once
• the genetic code is universal - each triplet codes for the same amino acid in every organism , this is indirect evidence for evolution.

Question 8

What are Introns used for?

Answer 8

They are not used or read by ribosomes but are removed in a process called splicing.

Question 9

What are the coding and non-coding regions of DNA called?

Answer 9

Exons are the coding sequences of bases while introns are the non coding sequences of bases.