Download Cells and Enzymes

Higher Biology for CfE
Homework
Unit 1 – DNA and the Genome
1.3 & 1.4
Name:______________________
Class:_________
Teacher:_____________________
1.3 Control of Gene Expression
1. The diagram below represents a stage in
protein synthesis in a cell.
2. Proteins may be modified after
translation
before
they
become
functional. The list shows changes which
could modify protein chains
1
2
3
Which line in the table below identifies
correctly molecules W, X and Y?
A
B
C
D
W
Molecules
X
Y
tRNA
polypeptide
mRNA
Polypeptide
mRNA
tRNA
tRNA
mRNA
polypeptide
mRNA
polypeptide
tRNA
cutting
and
combining
polypeptide chains
adding carbohydrates to the
protein chain
adding phosphates to the protein
chain
Which of these changes are
examples of post translational
modifications?
A
B
C
D
1, 2 and 3
2 and 3 only
1 and 2 only
1 and 3 only
(2)
3 a. DNA and RNA molecules are found in the cells of both eukaryotes and prokaryotes.
DNA molecules are double-stranded whereas RNA molecules are single-stranded.
i.
Give two other structural differences between DNA and RNA molecules.
1.___________________________________________________________
___________________________________________________________
2. __________________________________________________________
________________________________________________________(2)
ii.
Describe the function of RNA polymerase in the synthesis of a primary transcript.
_________________________________________________________________
_________________________________________________________________
__________________________________________(2)
iii.
In eukaryotic cells mRNA is spliced after transcription. Describe what happens
during RNA splicing.
_________________________________________________________________
_________________________________________________(1)
b.
Actinomycin D is an antibiotic which binds to DNA and inhibits transcription in
eukaryotes and prokaryotes. The graph below shows mRNA content of a cell over
a 24 hour period after actinomycin D was added.
i.
State the time taken for the mRNA content of the cell to drop by 70% of its starting
level.
____________ hours (1)
ii.
Explain why actinomycin D would not be suitable in the treatment of bacterial
infections in humans.
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
___________________________________(2)
4.
The diagram below shows the stages involved in the transcription and translation of a
eukaryotic gene. Both introns and exons are transcribed and then the primary transcript is
modified to produce the functional mRNA which is then translated.
a. State the difference between introns and exons.
_________________________________________________________________
_________________________________________________(1)
b. Name the enzyme responsible for the primary transcript.
________________________________________________________(1)
c. Name the process that involves the modification of the primary transcript to form
the functional mRNA.
________________________________________________________(1)
d. Describe how different functional mRNA molecules can be produced from the
same primary transcript sequence.
_________________________________________________________________
_________________________________________________(1)
e. Describe one way in which the polypeptide structure can be modified following
translation.
________________________________________________________(1)
5.
Sickle cell anaemia is a genetic disorder in which red blood cells contain the protein
haemoglobin S instead of normal haemoglobin. The DNA sequence in the allele for
haemoglobin S carries a mutation. The table below shows some mRNA codons and
the abbreviations of the amino acids they code for.
The diagram below shows sections of the DNA sequences that code for normal
haemoglobin and for haemoglobin S.
a. Use abbreviations from the table to complete the boxes in the diagram below to show
the amino acid sequence in the section of haemoglobin S given.
(1)
b. i. Name bond Y in the diagram. ____________________________
(1)
ii. The chains of amino acids are folded to give proteins their three-dimensional shape.
Name one bond or interaction which holds the chain in its three-dimensional shape.
________________________________________________________
(1)
iii. Explain why the change in the base sequence in haemoglobin S leads to a failure of
the protein to function normally.
_____________________________________________________________________
___________________________________________________(1)
1.4 Cellular Differentiation
1. Which line in the table below correctly
describes meristems?
Type of cell
present
Cell division
occurring
A
specialised
no
B
unspecialised
no
C
specialised
yes
D
unspecialised
yes
2. Which of the following statements
related to cell differentiation is
correct?
A. Meristems are regions of
differentiated cell types in plants
B. Embryonic stem cells can
differentiate into a limited range of
cell types
C. A differentiated cell only expresses
genes that produce proteins
characteristic of that cell type.
D. Adult tissue stem cells can
differentiate into all cell types.
3. The graph below shows the changes in number of
human stem cells in culture. The activity of the
enzyme glutaminase present in the cells over an
eight hour period is also shown.
How many units of glutaminase activity were recorded when the
cell number was 50% of its maximum over the 8 day period?
A. 3
B. 4
C. 8
D. 9