Jun 2013 Unit 2 Flashcards
Describe the role of centromeres in mitosis.
- Holds chromatids together;
2. Attaches (chromatids) to spindle
Homologous chromosomes carry the same genes but they are not genetically identical.
Explain why.
carry different alleles
The appearance of each chromosome in Figure 2 is different from those shown in
Figure 1. Explain why
Chromatids have separated
Other than independent segregation, give one way in which meiosis allows the production of genetically different cells
Crossing over of alleles
Explain how these results suggest that animal A is the most closely related to humans
1. (Only) one amino acid different / least differences / similar amino acid sequence / similar primary structure; 2. (So) similar DNA sequence
A student who looked at these results concluded that animals B and C are more
closely related to each other than to any of the other animals.
Suggest one reason why this might not be a valid conclusion.
- Compared with humans / not
compared with each other;
Cytochrome c is more useful than haemoglobin for studying how closely related
different organisms are. Suggest one reason why
- All organisms respire/have
cytochrome c
DNA helicase is important in DNA replication. Explain why
- Separates/unwinds/unzips strands/helix / breaks H-bonds;
2. (So) nucleotides can attac
Cytarabine has a greater effect on cancer cells than on healthy cells. Explain why
(Cancer cells/DNA) divide
Give one way in which antibiotics can prevent the growth of bacteria.
Prevent cell wall formation / cause (cell)
lysis / inhibit ribosomes / inhibit protein
synthesis / prevent DNA replication / affect
function of cell membrane;
Describe how bacteria can become resistant to antibiotics by vertical gene transmission.
cell division/
The doctors used samples of this bacterium taken from many patients in the hospital.
Explain why this was important.
different types of bacteria
Do these data support the conclusion that hypochlorite was the most effective at killing
this bacterium? Explain your answer.
(Yes) 1. Largest clear zone/diameter/mean (so more bacteria killed); (No) 2. Standard deviations of chlorhexidene overlap/share values; 3. (Overlap means difference) is not significant / is due to chance
Doctors in a different hospital repeated this investigation. They found that hypochlorite
had little effect on samples of P. aeruginosa they obtained. Suggest how this different
result may have arisen.
- Mutation (in bacterium);
2. Gene/allele for resistance;
The oxygen dissociation curve of the fetus is to the left of that for its mother. Explain
the advantage of this for the fetus.
- Higher affinity / loads more oxygen;
- At low/same/high partial pressure/pO2;
- Oxygen moves from mother/to fetus;
After birth, fetal haemoglobin is replaced with adult haemoglobin. Use the graph to
suggest the advantage of this to the baby
- Low affinity / oxygen dissociates;
- (Oxygen) to respiring
tissues/muscles/cells;
Hereditary persistence of fetal haemoglobin (HPFH) is a condition in which production of fetal haemoglobin continues into adulthood. Adult haemoglobin is also produced.
People with HPFH do not usually show symptoms. Suggest why
enough adult hb is also produced oxygen released
Use the information provided and your knowledge of the founder effect to explain why
Ellis-van Creveld syndrome occurs at a higher frequency in the Amish population than
in people in America who are not Amish.
1. Population formed by a small number of founders/people /30 people; 2. (Founders show) less genetic diversity / small(er) gene pool / less variety of alleles; 3. Individuals breed within group / do not breed with outsiders; 4. High(er) chance of inheriting allele (than in non-Amish population)
The faulty allele that causes Ellis-van Creveld syndrome is the result of a mutation of a
gene called EVC. This mutation leads to the production of a protein that has one
amino acid missing.
Suggest how a mutation can lead to the production of a protein that has one amino
acid missing.
- Change in tertiary structure/
active site; - (So) faulty/non-functional protein
/enzyme
Explain how water enters xylem from the endodermis in the root and is then transported to the leaves.
- Active transport by endodermis;
- (Of) ions/salts into xylem;
- Lower water potential in xylem /
water enters xylem by osmosis
/down a water potential gradient;
(Xylem to leaf) - Evaporation / transpiration (from
leaves); - (Creates) cohesion / tension /
H-bonding between water
molecules / negative pressure; - Adhesion / water molecules bind
to xylem; - (Creates continuous) water
column;
Suggest how a mutation can lead to the production of a protein that has one amino
acid missing.
loss of 3 bases
Abdominal pumping increases the efficiency of gas exchange between the tracheoles
and muscle tissue of the insect. Explain why
- More air/oxygen enters /
air/oxygen enters quickly/quicker; - (So) maintains/greater diffusion
or concentration gradient;
Explain how their small size enables gas exchange to be efficient without the need for
abdominal pumping.
short(er) diffusion distance
The insect opens its spiracles at a lower frequency in very dry conditions.
Suggest one advantage of this.
to prevent water loss
The ends of tracheoles connect directly with the insect’s muscle tissue and are filled
with water. When flying, water is absorbed into the muscle tissue. Removal of water
from the tracheoles increases the rate of diffusion of oxygen between the tracheoles
and muscle tissue. Suggest one reason why
Gases move/diffuse faster in air than through water
Apart from the size of the female, suggest two factors that should have been kept
constant in order to obtain reliable results.
concentration of skin lipid
same speices
The male snakes used for each trial were selected at random. Explain why this was
important.
To avoid bias;
The scientists used different male snakes in each trial. Suggest why.
1. To avoid change in (courtship) behaviour (due to past experience); 2. To observe a typical/general/representative (response)
What should the scientists have placed in the cage as a control, to show that males
were responding to lipids from females?
Filter paper without (skin) lipids
The scientists concluded that male snakes showed more courtship behaviour towards
long female snakes and to lipids from the skins of long females.
Explain one other conclusion that can be made from the data.
- Similar response to lipids and
(whole) snakes; - (So males are) responding to
lipids
Suggest two advantages of male snakes courting with longer females.
(Parent/offspring) 1. Produce more/larger offspring/eggs; 2. Better predators / fitter / more successful at gaining food / less likely to be eaten / more able to protect offspring/eggs;
Use Figure 3 and Figure 4 to suggest why male garter snakes show greater courtship
behaviour to longer female snakes.
- (Males) respond to/sense
(unsaturated) fatty acids; - (Long females) produce/have
more fatty acids / positive
correlation
Describe how Figure 4 could be used to predict the percentage of unsaturated fatty
acids produced by female garter snakes of body length greater than 75 cm.
- Draw a line of best fit;
2. Extrapolation / extend line;
The females of other species of snake secrete lipids on their skin. These lipids also
contain unsaturated fatty acids. Male garter snakes do not show courtship behaviour
towards these females. Suggest why
produce different fatty acids;
