Page 28 - CB1.3 Genetic Varation sciPAD

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28 CB 1.3 GENETIC VARIATION
PRINCIPLES OF GENETIC VARIATION
C G C
C A
G G
T A A
G
Hints for answering
these questions
3. DNA is made up of repeating units called nucleotides.
(a) Label the nucleotide shown below.
G
(b) The bases within a DNA molecule pair up according to their different chemical
makeup. Scientists call this the ‘complementary base-pairing rule’.
Use the base-pairing rule to complete the DNA strand shown below.
4. Read the following sentence and answer the questions that follow.
“The ability to roll your tongue may be controlled by a gene. People who can roll
their tongue have the allele ‘R’, while those who cannot roll their tongue do not.”
(a) What ‘trait’ is the text referring to? 


(b) Explain how someone could have two different alleles for the same gene.









Nucleotides
are made of a
phosphate, a sugar
and a base.
There are four bases
(A, T, C, G). The
‘straight’ letters go
together and the
‘curved’ letters go
together.
Use ‘genetically
determined’ in your
answer
Discuss where your
chromosomes come
from (i.e. half from
your father and the
other half from your
mother). Use this to
explain the answer.
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