set b Flashcards
The student prepared a temporary mount of the onion tissue on a glass slide. She
covered the tissue with a cover slip. She was then given the following instruction.
“Push down hard on the cover slip, but do not push the cover slip sideways.”
Explain why she was given this instruction.
- Push hard – squash tissue;
- Not push sideways – breaking chromosomes;
The student concluded that the cell in Figure 1 was in the anaphase stage of mitosis.
Give two reasons for this conclusion.
- Chromosomes are
at poles of spindle - that centromeres of (sister) chromatids have been pulled apart
Suggest why galactose and glucose cannot pass through the plasma membrane into intestinal cells
by simple diffusion through the phospholipid bi-layer.
- they are too large
What two substances are required to break the glycosidic bond in lactose?
- water
- enzyme
A gene codes for the production of lactase. This gene is normally switched off after an infant moves to
adult food. Almost all adult mammals are unable to digest lactose. They are said to be lactose intolerant. Humans are an exception. Most humans have a genetic mutation that prevents the shutdown of lactase production.
State what structural detail of a polypeptide is altered by gene mutations.
- sequence of amino acids
Some humans are lactose intolerant. Milk can be treated with lactase to reduce the concentration
of lactose present. Fresh milk is passed over lactase molecules immobilised on a suitable matrix. Give two economic advantages of immobilising enzymes for large-scale production.
- re-used so less cost
- more profit from faster yield
- purifying cost reduced
Suggest how the lactose intolerance phenotype came to be present in only 5% of a population like the
Europeans, but came to be present in 97% of the Australian aborigines. Use the information given
above and knowledge of Darwin’s theory of evolution by natural selection.
europeans -
- availabillty of milk acted as a selection pressure
- individuals with non tolerance allele has a better chance of survival
- genetic drift
- directional selection
australian aborigines -
- ancestral population pre agriculture
- so no selection for non tolerance allele
- no gene flow
- no selection pressure
An Iron Age farm was excavated by archaeologists. Some DNA was recovered from the tooth of an
animal thought to be a type of domesticated milk cow.
A farmer keeps rare breed cows similar to those farmed on the Iron Age farm. DNA from the cows
was obtained.
What technique would you plan to use, to compare digested and amplified fragments from the two
DNA samples?
- electropheresis
In humans, when core body temperature falls below 35°C, positive feedback causes this
decrease in core body temperature to continue. This process is known as hypothermia.
Explain how positive feedback could accelerate the process of hypothermia.
- positive feedback is when the initial change is further increased
- lower temperature reduces kinetic energy
- enzyme activity reduced
- metabolism reduced
- less metabolic heat generated
- body temp drops further
Agammaglobulinemia and Vici syndrome are both genetic diseases. Agammaglobulinemia results in a lack of mature B lymphocytes in a person’s blood. Suggest and explain one symptom of agammaglobulinemia.
- greater susceptibility to infection
- fewer antibodies
DNA profiling can be used to analyse the risk of inheriting conditions such as agammaglobulinemia and Vici syndrome. To produce a DNA profile, DNA first needs to be purified. Explain why a protease enzyme is added to the mixture during the DNA purification
process.
- breaks down proteins associated with dna
State how the cytoskeleton moves organelles around the cell.
- using microtubules
Epithelial cells in the airways of mammals play an essential role in defences against
pathogens.Explain the function of epithelial cells in the airways of mammals in the defence against
pathogens and suggest the importance of the cytoskeleton in carrying out this function.
- goblet cells secrete mucus
- mucus traps pathogens
- cillia waft mucus
- cytoskeleton moves the cillia
The process of ultrafiltration in the kidney shares similarities with the formation of tissue fluid.
Describe the similarities and differences between ultrafiltration and the formation of tissue
fluid.
- both involve high hydrostatic pressure
- in both hydrostatic pressure is greater than oncotic pressure
- small molecules move out the blood
- large molecules remain in the blood
-both involve basement membrane - both occur in the capillaries
- knot of capillaries in ultrafiltration and a network of capillaries in tissue fluid formation
- in ultrafiltration, the molecules are filtered in 3 layers(basement membrane, podocytes and endothelium) whereas in tissue fluid formation there is only one layer of filtering(basement membrane)
Suggest two characteristics of a patient that must be taken into account when using this
GFR measurement to diagnose kidney damage.
Explain why each characteristic must be considered.
- age as kidney function declines with age
- gender as men and women have different muscle mass
- diet, affects the level of creatine
