genes and the genetic code

Question 1

what is a gene

Answer 1

-a section of DNA containing coded information in the form of specific bases
-codes for amino acid sequence of polypeptide
-functional RNA

Question 2

what is a locus

Answer 2

a specific, fixed position on a chromosome where a particular gene is located.

Question 3

what reasoning did scientists have to suggest that there must be a minimum of 3 bases that coded for each amino acid

Answer 3

-only 20 amino acids occur regularly occur in proteins
-only four bases in DNA
-each amino acid must have its own code of bases
-if each base coded for a different amino acid there would only be 4 amino acids
-using a pair of bases (16 codes) means there is not enough codes
-three is enough (64 codes)

Question 4

what is a degenerate code

Answer 4

when multiple codons code for the same amino acid

Question 5

T/F amino acids are coded by only one codon

Answer 5

F–> only a few are

Question 6

what does the start of a DNA sequence that codes for a polypeptide always have

Answer 6

a triplet that codes for the amino acid methionine

Question 7

what happeneds if the first methionine amino acid doesn’t form part of the final polypeptide structure

Answer 7

it is later removed

Question 8

what are stop codons

Answer 8

three triplets that mark the end of a polypeptide chain

Question 9

what does it mean if the code is non overlapping

Answer 9

each base in the sequence is only read once

Question 10

what does it mean if the code is universal

Answer 10

-each triplet codes for the same amino acid in all organisms
-indirect evidence for evolution

Question 11

what are exons

Answer 11

base sequences that code for amino acids

Question 12

what are introns

Answer 12

non coding sequences