The genetic code

Question 1

How many different
bases are there in
DNA?

Answer 1

4

Question 2

How many common
amino acids are
there?

Answer 2

20

Question 3

How many possible

codons are there?

Answer 3

64

Question 4

What is a codon?

Answer 4

A sequence of

3 bases

Question 5

Why are there 64

possible codons?

Answer 5

4 possible bases in 3
possible positions, 4 x
4 x 4

Question 6

What is a gene?

Answer 6

A sequence of bases
which code for a
protein

Question 7

What does
degenerate mean
when applied to the
genetic code?

Answer 7

Some amino acids are
coded for by more
than one codon

Question 8

What is the start code sequence?

Answer 8

AUG

Question 9

How many start

codons are there?

Answer 9

1

Question 10

How many stop

codons are there?

Answer 10

3

Question 11

What is the function

of a stop codon?

Answer 11

They indicate when
translation is
complete and the
protein has been
sythesised

Question 12

What does non-

overlapping mean?

Answer 12

There is no sharing of
bases between
codons

Question 13

Why is the genetic
code described as
universal?

Answer 13

all living organisms use

the same genetic code

Question 14

What is the advantage
of a non-overlapping
code?

Answer 14

It means there is no
restriction on the
amino acids you have
in a protein

Question 15

What does the
universal nature of
DNA suggest?

Answer 15

That all organisms
originate from a
common ancestor

Question 16

What are advantages
of the genetic code
being degenerate?

Answer 16

-means if a mutation
were to occur a
protein could still be
reduces and it
minimises the
deletious effects pf
mutations

Question 17

How do mutations to
a gene affect the
structure of a protein?

Answer 17

-change in base could
lead to change in
amino acid produced
-this amino acid
would have a different
R-group to the
original amino acid
-the R-group might
interact differently
with other R-groups
-the folding of the
tertiary structure is
affected

Question 18

How many proteins

does 1 gene code for?

Answer 18

1

Question 19

What does a gene
being switched on
mean?

Answer 19

The gene is actively
being used to
produce proteins

Question 20

If all cells contain the
same DNA, how can
cells specialise?

Answer 20

-different genes are
switched on and off in
different cells