Question 1
1
Rice (Oryza sativa) is usually intolerant to sustained submergence under water, although it grows rapidly in height for a few days before dying. This is true for one variety, Oryza sativa japonica. The variety Oryza sativa indica is much more tolerant to submergence. Three genetically modified forms of O. sativa japonica, GMFA, GMFB and GMFC, were made using different fragments of DNA taken from O. sativa indica. The plants were then submerged for a period of 11 days. The heights of all the plants were measured at the beginning and at the end of the submergence period.
14 marks
Question 1(e)
1(e)
In the same experiment, the researchers hypothesized that the capacity to survive when submerged is related to the presence of three genes very close to each other on rice chromosome number 9; these genes were named Sub1A, Sub1B and Sub1C. The photograph below of part of a gel shows relative amounts of messenger RNA produced from these three genes by the submergence-intolerant variety, O. sativa japonica, and by the submergence-tolerant variety, O. sativa indica, at different times of a submergence period, followed by a recovery period out of water.
5 marks
Question 1(e)(i)
1(e)(i)
Determine which gene produced the most mRNA on the first day of the submergence period for variety O. sativa japonica.
Mediumstructured1 marks
Answer
Sub1C
Question 1(e)(ii)
1(e)(ii)
Outline the difference in mRNA production for the three genes during the submergence period for variety O. sativa indica.
Mediumstructured2 marks
Answer
Sub1A is expressed strongly/the most / Sub1A produces the most RNA; Sub1B (always) has the lowest expression/produces least mRNA; Sub1A expressed/produces mRNA for the longest time/days 1 to 10; Sub1C expressed/produces mRNA for the shortest time/days 3 to 7;
Question 1(e)(iii)
1(e)(iii)
Compare the mRNA production for the three genes during the submergence period between the two varieties.
Hardstructured2 marks
Answer
Sub1A only expressed/produces mRNA in indica / not/never expressed/ never produces mRNA in japonica; Sub1C expressed/produces mRNA from day 1 in japonica, but not indica; Sub1B has lower expression/production of mRNA than Sub1C in both varieties; other accurate comparisons;
Question 1(f)
1(f)
Deduce, using all the data, which gene was used to modify GMFC.
Hardstructured2 marks
Answer
Sub1A; is only expressed in indica; indica is the variety showing submersion tolerance;
Question 1
1
Obesity (excessive weight) is recognized as a global health problem and has been correlated with a large number of health issues, diseases and deaths. The increased consumption of fructose, now widely used as a sweetener, has been associated with the increase in obesity. In a study, mice were divided into four groups. Each group was given the same amount of food and either a soft drink with a different sweetener or water.
15 marks
Question 1(e)
1(e)
Studies investigated the role of glucose and fructose in the development of pancreatic cancer cells. Pancreatic cancer cells were grown in equal concentrations of each sugar and the uptake of each into ribose-producing pathways was measured. The graph shows the range of uptake of sugars and the mean value. Discuss whether the results provide clear evidence of a difference in uptake.
Harddata_response2 marks
Answer
glucose has a much greater range of uptake / vice versa; but a (much) lower mean/uptake / vice versa; there is no overlap (so there is clear evidence);
Question 1(g)
1(g)
Suggest how sugar uptake might be related to pancreatic cancer.
Hardshort_answer2 marks
Answer
cancer is uncontrolled mitosis/cell division; sugar is an energy source/nutrient needed for mitosis/cell division; ribose is used to produce nucleic acids/DNA/RNA; production of nucleic acid is necessary for mitosis;
Question 1
1
Type I diabetes is a leading cause of death in advanced countries and is associated with various severe or fatal complications, including blindness, kidney failure, heart disease, stroke, neuropathy, and amputations. Embryonic stem cells are considered to be a powerful tool in the treatment of diabetes. In a study, embryonic stem cells were grown in culture and tested for insulin mRNA. A drug was injected into two groups of healthy mice in order to simulate type I diabetes 15 days prior to the transplant of embryonic stem cells. The mice in the transplant group received embryonic stem cells that produce insulin mRNA. The control group did not receive the transplant. The graph shows the blood glucose concentration in both groups.
18 marks
Question 1(g)
1(g)
Insulin is produced by cutting C -peptide from the precursor molecule proinsulin. Suggest why group 1 has a greater level of C-peptide than group 2.
Mediumstructured2 marks
Answer
a. more pancreatic beta-cell/ß-cell function/more insulin «production»/less severe diabetes in group 1 b. stem cell transplant is more successful/more effective/more stem cells survived in group 1 c. «group \(1 »\) produces more proinsulin Do not accept answers suggesting that only Group 1 produces insulin, Reject more C-peptide. 2 max
Question 1
1
Auxin can be used to promote the development of roots from stem and leafy cuttings in some plants. In a study into the distribution of auxin in the development of these roots, scientists measured the amount of auxin in different leaves of a shoot tip of Petunia hybrida. The figure indicates the numbering of leaves on the shoot, from L1 as the youngest and smallest to L6 as the largest and oldest leaf. The developmental stage of L5 and L6 was very similar, so L5 was not analysed. The stem base is the lowest part of the cutting where roots may form. The graph shows the auxin concentration in the different leaves.
13 marks
Question 1(f)
1(f)
The scientists wanted to know whether the accumulation of auxin over time in the stem base of the controls affected expression of the GH3 gene, known to have a role in growth regulation in different plants. The technique that was used to quantify the level of transcription of the GH3 gene was Northern blotting. In this procedure the darkness and thickness of the band is an indicator of the level of transcription of a particular gene. The image shows the result of the Northern blot from 2 hours to 24 hours after cutting.
5 marks
Question 1(f)(i)
1(f)(i)
State the name of the molecule which is produced by transcription.
Easystructured1 marks
Answer
mRNA/RNA
Question 1(f)(ii)
1(f)(ii)
Compare the pattern of GH3 transcription with the pattern of auxin concentration in the stem base control cuttings. You may use the table provided to help you to record the patterns before you compare them. (Please note: a simple comparison in the table will not gain marks)
Mediumstructured2 marks
Answer
ii a. at 2 and 24 hours, auxin levels are similar and at 2 and 24 hours G H 3 levels are similar b. the pattern for the formation of auxin is similar to the pattern of transcription of the GH3 gene OR both decrease and then increase c. «however» there is a lag between the peaks of the GH3 transcription and the peaks of auxin A comparison must be made to award marks. Do not award marks for simple completion of the table. 2 max
Question 1(f)(iii)
1(f)(iii)
The scientists concluded that auxin activates the transcription of the GH 3 gene. Using the information on the auxin concentration in the stem base in the graph on page 4 and the Northern blot, evaluate whether this conclusion is supported.
Mediumstructured2 marks
Answer
a. the data «partially» supports the conclusion OR the relationship is not clear b. the auxin concentration «seems to» rise before the transcription level increases OR there is a lag between auxin concentration changing and transcription level changing OR the auxin concentration falls before the transcription level falls c. more data is needed «before two hours/after 24 hours» To award mp b, awareness of the lag should be demonstrated OWTTE 2 max
Question 1
1
The Chinese soft-shelled turtle, Pelodiscus sinensis, lives in salt water marshes. The turtle can live under water and out of water. These turtles have fully developed lungs and kidneys, however, many microvilli have been discovered in the mouth of P. sinensis. A study was undertaken to test the hypothesis that oxygen uptake and urea excretion can simultaneously occur in the mouth. Initial experiments involved collecting nitrogen excretion data from P. sinensis. The turtle urinates both in water and out of water. When in water it allows waste products to be washed out of its mouth. When out of water it regularly dips its head into shallow water to wash its mouth. The table shows the mean rates of ammonia and urea excretion from the mouth and kidney over six days.
18 marks
Question 1(e)
1(e)
Further research was conducted to determine where mRNA expression of a urea transporter gene might be occurring in P. sinensis. Gel electrophoresis was used to analyse different tissue samples for mRNA activity. Outline the additional evidence provided by the gel electrophoresis results shown above.
Hardstructured2 marks
Answer
a. mRNA only in mouth and tongue/in mouth and tongue but not esophagus intestine kidney or bladder b. bands / lines indicate mRNA for/expression of urea transporter gene c. urea transporter gene expressed / urea transporters in mouth/tongue / not expressed/made in esophagus/intestine/kidneys/bladder d. mRNA/transcription/gene expression/urea transporters higher in tongue/more in tongue «than mouth»» 2 max
Question 1
1
Organisms often release chemicals when attacked as part of their defence system. Scientists studied lima bean plants (Phaseolus lunatus) infested with either an armyworm, Spodoptera exigua, or a herbivorous mite, Tetranychus urticae. Both organisms feed on lima bean leaves, causing the leaves to release chemicals.
13 marks
Question 1(d)
1(d)
The scientists then used the transcribed DNA of each treatment to study the activation of three genes of the plants' defence system. The DNA was separated by gel electrophoresis. The activation was tested one hour after treatment and again after 24 hours. Gene 3 Deduce, with a reason, which gene is first transcribed when exposed to C2.
Mediumstructured1 marks
Answer
gene 1 is first transcribed «after C2 treatment» as it shows activation after one hour
Question 4
4
Where in the cell do condensation reactions involving amino acids occur? A. Nucleus B. Golgi apparatus C. Ribosomes D. Lysosome
Mediummcq1 marks
Answer
C
Question 6
6
This is a sequence of nucleotides from a section of mRNA. AUGAAACGCACGCAG From which DNA sequence has it been transcribed? A. ATGAAACGCACGCAG B. UACUUUGCGUGCGAC C. TACUUUGCGTGCGTC D. TACTTTGCGTGCGTC
Mediummcq1 marks
Answer
D
Question 6
6
The table shows information on the genetic code of four different mRNA sequences. Which sequence demonstrates degeneracy in the genetic code? \begin{tabular}{|l|l|} \hline mRNA sequence & Amino acids \\ \hline UUU UUA UCU & Phe Leu Ser \\ \hline CUU CCU CUU & Leu Pro Leu \\ \hline AUG ACG AAG & Met Thr Lys \\ \hline GUU GGU GUG & Val Gly Val \\ \hline \end{tabular}
Mediummcq1 marks
Answer
D
Question 6
6
What occurs during translation? I. Polypeptides synthesised on ribosomes II. RNA polymerase catalyses polypeptide synthesis III. Complementary base pairing between codons and anticodons I and II only I and III only II and III only I, II and III
Mediummcq1 marks
Answer
B