Incorrect Answers For Paper 2 Flashcards
When explaining the benefit if an enzyme involved in respiration, what should you always mention?
That the processes the enzyme aids provides ATP.
Dengue is a serious disease that is caused by a virus. The virus is carried from
one person to another by a mosquito, Aedes aegypti. One method used to try to
reduce transmission of this disease is the Sterile Insect Technique (SIT). This
involves releasing large numbers of sterile (infertile) male A. aegypti into the
habitat. These males have been made infertile by using radiation.
0 2 . 1 Explain how using the SIT could reduce transmission of dengue.
-Males are infertile, so there is more infraspecific competition between the males.
-Do not reproduce.
The release of radiation-sterilised A. aegypti has not been very successful in
controlling the transmission of dengue.
Suggest one reason why.
Radiation affects their courtship.
If there are more mitochondria, what will there also be an increase in?
Increase in aerobic respiration.
The scientists then compared the length of time that the control mice and the
trained mice could carry out prolonged exercise. The trained mice were able to
exercise for a longer time period than control mice.
Explain why.
-More aerobic respiration produces more ATP
-Anaerobic respiration delayed.
-Less lactate.
The solution that the student used to produce the chloroplast suspension had the
same water potential as the chloroplasts.
Explain why it was important that these water potentials were the same.
-So that osmosis did not occur.
-So that the chloroplasts did not lyse.
In an investigation using DCPIP to investigate the light dependent reaction, why would a test tube with no chloroplasts and only DCPIP solution be set up?
-To show that chloroplasts are required for the light dependent reaction.
-To show that light does not affect DCPIP.
Explain why a test tube containing chloroplasts and DCPIP solution would turn colourless after 30 minutes in light.
-Reduction of DCPIP by electrons.
-From chlorophyll/light dependent reaction.
The student evaluated the effectiveness of different chemicals as weed-killers by
assessing their ability to prevent the decolourisation of DCPIP in chloroplast
suspensions.
He added different concentrations of each chemical to illuminated chloroplast
suspensions containing DCPIP. He then determined the IC50 for each chemical.
The IC50 is the concentration of chemical which inhibits the decolourisation of
DCPIP by 50%.
Explain the advantage of the student using the IC50 in this investigation.
It provides a standard reference point.
When linking a slow LDR to the LIR, what must you always say?
Less ATP produced
Less NADPH produced
Less GP is reduced to TP
Explain why an increase in shoot biomass can be taken as a measurement of
net primary productivity.
-It represents the mass of carbon produced by the plant.
-Represents the gross production minus respiratory losses.
What is meant by phenotype?
-Expression due to the genotype.
-Expression due to the environment as well.
One way to detect and measure accurately the amount of RNA in a tissue sample
is by RT-PCR (reverse transcriptase-polymerase chain reaction).
RT-PCR uses a reaction mixture containing:
• the sample for testing
• reverse transcriptase
• DNA nucleotides
• primers
• DNA polymerase
• fluorescent dye.
Any DNA in the sample is hydrolysed by enzymes before the sample is added to
the reaction mixture.
Explain why.
-To remove any DNA present.
-As this DNA would be amplified and replicated.
Scientists have used the RT-PCR method to detect the presence of different RNA
viruses in patients suffering from respiratory diseases.
The scientists produced a variety of primers for this procedure.
Explain why.
Base sequences differ.
So different complementary primers are required.
In an isolated population, why might there be a high frequency of a certain mutation?
-Isolated so there is inbreeding/low genetic diversity.
-Allele is inherited through generations from a common ancestor.
This autosomal dominant mutation involves a change in triplet 280 from GAA to
GCA. Scientists analysed chromosome 14 from 102 individuals from Yaramul.
They recorded a sample size of 204 and detected 75 E280A mutations but only
74 potential AD cases. The scientists identified individuals with the mutation by
whole genome sequencing. They had decided that a DNA probe would not be a
suitable method to detect the E280A mutation.
Suggest why a DNA probe for the mutated triplet was not considered a suitable
method for detection of the E280A mutation
GCA triplet is common and found in other places.
Would be unable to determine if it was the mutation or a false positive.
What is always needed after saying the myosin heads binds to the actin-myosin head?
AND performs the power stroke.
The scientists first produced transgenic poplar trees. These trees all had a length
of foreign DNA inserted into them. This DNA led to the production of single-
stranded RNA that specifically inhibited expression of the gene for PIP1.
The scientists then measured the difference in the amount of PIP1 in leaves of
transgenic poplars and in leaves of wild type poplars without the foreign DNA. The
amount of PIP1 in the transgenic poplars was approximately 15% of that in the wild
type poplars.
Using this information, what can you conclude about the effect of the foreign DNA in
the transgenic poplar trees?
-Single stranded RNA has base sequence complementary to PIP1 mRNA.
-Binds to mRNA of PIP1 and leads to its destruction.
-Prevents translation of PIP1.
-Reduces photosynthesis.
Suggest one reason why it was important that the student left the apparatus for one
hour after the yeast culture reached a constant temperature.
So that the oxygen is absorbed/respired.
(Cannot say acclimatise).
What is the final step when determining the mean percentage cover of a species in a particular area?
Divide the total percentage by the number of quadrats.
What do pioneer species do when they inhabit an area of land?
They change the abiotic conditions to make them less hostile.
In an experiment investigating the kidney function, explain why it is important to give all of the volunteers the same food for several days before starting the experiment?
-It will affect the water potential of the blood.
-It will affect the volume of urine.
Furosemide inhibits the absorption of sodium and chloride ions from the filtrate
produced in the nephrons.
Explain how furosemide causes an increase in the volume of urine produced.
-Na+ and Cl- ions remain in the filtrate.
-Filtrate has a more negative water potential.
-Less water is reabsorbed via osmosis from the tubule.
-Collecting duct is where osmosis occurs.
In genetic crosses, the observed phenotypic ratios obtained in the offspring are often
not the same as the expected ratios.
Suggest reasons why.
-Fertilisation is random
-Epistasis
-Linked genes
In a genetic cross with two genes, what causes there to be most of the dominant-dominant (1860) and recessive-recessive (580) phenotypes, and very low numbers of dominant-recessive (68 + 57) phenotype?
-The genes are linked.
-Produces fewer dominant-recessive offspring.
-This is because crossing over has occurred.
What is the expected phenotype ratio when a dihybrid is performed and the genes for height of plant and for the type of leaf were on
different homologous pairs of chromosomes?
9:3:3:1
What must you always say when talking about neurotransmitter movement?
The neurotransmitter diffuses across the synapse.
Dopamine has a role in numerous processes in the brain including pain relief. The
release of dopamine can be stimulated by chemicals called endorphins produced in
the brain. Endorphins attach to opioid receptors on presynaptic neurones that release
dopamine.
Morphine is a drug that has a similar structure to endorphins and can provide pain
relief.
Explain how.
Morphine has a similar tertiary structure to endorphins, so can bind to the same complementary opioid receptor on the pre synaptic membrane, which causes dopamine to be released.
Soybeans are used in a number of processed foods. However, soybeans contain a
protein known as P34 that causes an allergic response in some people. Scientists
have created transgenic soybeans that produce single-stranded cDNA, which
prevents transcription of the P34 gene. They used recombinant plasmids as vectors
to transform soybean cells. After they had screened these cells for production of the
P34 protein, they cultured the transformed cells to form soybean plants.
Suggest how single-stranded cDNA could prevent transcription of the P34 gene.
cDNA binds to the promoter region of the P34 gene.
What is the prevention of transcription always related to?
A transcription factor or protein binding to the promoter region of the DNA.
What is the prevention of translation of a gene always linked to?
The binding is siRNA or miRNA to the mRNA of that gene followed.
The soybean cells were screened for the presence of the P34 protein. This process
involved the use of gel electrophoresis to separate proteins extracted from soybean
cells.
Suggest two features of the structure of different proteins that enable them to be
separated by gel electrophoresis.
-They have a varying lengths of polypeptide chain.
-Charge.
-R groups differ.
Lactose is the main sugar in milk and is hydrolysed by the enzyme lactase. Lactase is
essential to newborn mammals as milk is their only source of food. Most mammals
stop producing lactase when they start feeding on other food sources. Humans are
an exception to this because some continue to produce lactase as adults. The ability
to continue producing lactase is known as lactase persistence (LP) and is controlled
by a dominant allele. A number of hypotheses based on different selection pressures
have been put forward to explain LP in humans.
0 9 . 1 One hypothesis for LP in humans suggests that the selective pressure was related to
some human populations farming cattle as a source of milk.
Describe how farming cattle as a source of milk could have led to an increase in LP.
-LP is due to a mutation.
-Milk provides glucose.
-Individuals with allele are more likely to survive AND reproduce.
-Frequency of allele increases in the next generation.
Lactase persistence is caused by a mutation in DNA. This mutation does not occur in
the gene coding for lactase.
Suggest and explain how this mutation causes LP.
-Mutation in the gene for the transcription factor.
-Lactase gene continues to be transcribed.
When discussing how cones improve visual acuity, what must you always say?
That cones send separate sets of impulses to the brain, whereas rods send a single set of impulses the brain.
People with red-green colour blindness are unable to distinguish between red and
green, and also between other colours.
Explain why.
-Green sensitive pigment is non-functional.
-There are three different types of cone cell.
-Other colours are seen
Due to the stimulation of more than one cone.
When discussing pluripotent stem cells, what must always be stated about their growth?
-iPS cells divide.
-AND differentiate.
Benefits of using iPS cells over gene therapy?
-Use of iPS cells is long-term.
-Less chance of an immune response using iPS cells.
-Use of iPS cells is a single treatment.
-Harm/side effects from using viruses in gene therapy.
Why does the blinding of more insulin to muscle cells increase the rate of respiration?
-Insulin leads to more transport proteins for glucose.
-More glucose can be absorbed via facilitated diffusion for use in respiration.