Author: Lindsey Delve

Carmel College

DNA and Protein synthesis Math HW
Name___________________________ MEG______  Tutor_____________________
Q1.          S       The diagram shows a single-celled organism called Chlamydomonas.

(b)     A Chlamydomonas cell has two flagella. These flagella contain a single sort of protein. A flagellum consists of a bundle of 242 filaments. Each filament consists of 7500 protein molecules. Each protein molecule contains 900 amino acid units.
(i)      What would be the minimum number of nucleotides in the coding region of the mRNA used to synthesise this protein?
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(1)

(ii)     In an investigation, a culture of Chlamydomonas was treated in a way that caused them to lose their flagella without any other damage to the cells. The flagella grew back to their original length in 60 minutes.
How many amino acid molecules would be incorporated into each growing flagellum per minute? Show your working.

 
 
Answer .........................................
(2)

(c)     The researchers investigated the rate at which the flagella grew in three different media.
1.      A medium containing actinomycin D, which prevents transcription by binding to the guanine in DNA
2.      A medium containing puromycin, which prevents translation by attaching to ribosomes
3.      A control medium
The results are shown in the graph.

(i)      Describe how the rate of growth was affected by puromycin.
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(2)

(ii)     The researchers concluded
1.       that the cells used mRNA that is already present in the cytoplasm for the regrowth of the flagella;
2.       that some of the regrowth uses protein molecules already present in the cell.
Explain the evidence for each of these conclusions.
1 ..........................................................................................................
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2 ..........................................................................................................
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(4)

Q2.Haemoglobin is a protein. It is made of two alpha polypeptides and two beta polypeptides. Each alpha polypeptide has 141 amino acids and each beta polypeptide has 146 amino acids.

(b)     Calculate the minimum number of DNA bases needed to code for the number of amino acids in one alpha polypeptide.
Answer = ...............................
(1)

Q3.(b)     Scientists investigated the effect of not being able to produce creatine on the force produced by muscle. They used mice with a mutation that made them not able to produce creatine.
The force produced when these mice gripped with their paws was compared with the force produced by normal mice that were able to produce creatine.
The graph shows the scientists’ results.

(i)	What was the percentage fall in the mean force produced by mice not able to produce creatine, compared with the normal mice? Show your working.

Answer ........................... %
(2)

Q4.The Amish are a group of people who live in America. This group was founded by 30 Swiss people, who moved to America many years ago. The Amish do not usually marry people from outside their own group.
One of the 30 Swiss founders had a genetic disorder called Ellis-van Creveld syndrome. People with this disorder have heart defects, are short and have extra fingers and toes. Ellis-van Creveld syndrome is caused by a faulty allele.
In America today, about 1 in 200 Amish people are born with Ellis-van Creveld syndrome. This disorder is very rare in people in America who are not Amish.
(a)     In America today, there are approximately 1250 Amish people who have Ellis-van Creveld syndrome. Use the information provided to calculate the current Amish population of America.

 

Amish population .....................................
(1)

Q5.       

Scientists investigated three genes, C, D and E, involved in controlling cell division.
They studied the effect of mutations in these genes on the risk of developing lung cancer.
The scientists analysed genes C, D and E from healthy people and people with lung cancer.
•        If a person had a normal allele for a gene, they used the symbol N.
•        If a person had two mutant alleles for a gene, they used the symbol M.
They used their data to calculate the risk of developing lung cancer for people with different combinations of N and M alleles of the genes. A risk value of 1.00 indicates no increased risk. The following table shows the scientists’ results.
 
| Gene C | Gene D | Gene E | Risk of developing lung cancer
| N | N | N | 1.00
| M | N | N | 1.30
| N | N | M | 1.78
| N | M | N | 1.45

N = at least one copy of the normal allele is present
M = two copies of the mutant allele are present

(b)     What do these data suggest about the relative importance of the mutant alleles of genes C, D and E on increasing the risk of developing lung cancer? Explain your answer.
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(3)

 

M1.        
(b)     (i)      2700
1
(ii)      = 27 225 000 / 27 × 10^6 = 2 marks
(allow 1 mark for principle: )
2

(c)     (i)      rate slightly slower / not affected in first 20 / 30 minutes / lower
peak than control;
then decreases / much lower (than control);
(allow 1 mark for increase in first 20 / 30 minutes, then decreased, if not compared with control / normal)
(disqualify flagellum grows longer)
2
(ii)     1.       actinomycin has no effect (on growth of flagella);
          even though mRNA production / transcription prevented;
(accept references to ‘expt 1’)
2.       (re)growth little affected by puromycin at first;
protein synthesis inhibited, so likely to be using proteins
present;
4

M2.   (b)     423;
1
M3   (b)     (i)      Any value between 68.5 and 69.49 (%);;
If get difference of 0.9 but calculation of percentage incorrect, then award 1 mark;
2
M4.(a)     250 000;
1
M5
(b)     1.      (Mutation) in E produces highest risk / 1.78;
2.      (Mutation) in D produces next highest risk / 1.45;
3.      (Mutation) in C produces least risk / 1.30;
Must be stated directly and not implied
E > D > C = 3 marks
Accept: values of 0.78, 0.45 and 0.30 for MP1, MP2 and MP3 respectively
If no mark is awarded, a principle mark can be given for the idea that all mutant alleles increase the risk
3