Holstein Friesian cattle are a breed of cattle used by dairy farmers in many countries of the world for the high milk yield of their cows. Fig. 4.1 shows Holstein Friesian cattle. Milk yield in Holstein Friesian cattle is affected by heat stress. Heat stress occurs when homeostatic mechanisms are not enough to keep the body temperature down to normal levels. One of the factors that contributes to heat stress is air temperature. Fig. 4.2 shows: - the mean daily air temperature in Central Europe - the mean monthly milk yield per cow of Holstein Friesian cattle in Central Europe. The SLICK allele differs from the recessive allele by a single nucleotide deletion. This results in a frameshift mutation and introduces a premature stop codon in the PRLR gene. Scientists can use gene editing to replicate this mutation in Holstein Friesian cattle. This provides a way to introduce the SLICK allele into Holstein Friesian cattle without selective breeding. Compare gene editing and selective breeding for introducing the SLICK allele into Holstein Friesian cattle. Include similarities and differences in your answer. ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . .........................................................................................................................................
Exam No：9700_m24_qp_42 Year：2024 Question No：4(d)
Answer:
Knowledge points:
12.2.1.1 glycolysis in the cytoplasm
12.2.1.2 link reaction in the mitochondrial matrix
12.2.1.3 Krebs cycle in the mitochondrial matrix
12.2.1.4 oxidative phosphorylation on the inner membrane of mitochondria
12.2.10 outline respiration in anaerobic conditions in mammals (lactate fermentation) and in yeast cells (ethanol fermentation)
12.2.11 explain why the energy yield from respiration in aerobic conditions is much greater than the energy yield from respiration in anaerobic conditions (a detailed account of the total yield of ATP from the aerobic respiration of glucose is not expected)
12.2.12 explain how rice is adapted to grow with its roots submerged in water, limited to the development of aerenchyma in roots, ethanol fermentation in roots and faster growth of stems
12.2.13 describe and carry out investigations using redox indicators, including DCPIP and methylene blue, to determine the effects of temperature and substrate concentration on the rate of respiration of yeast
12.2.14 describe and carry out investigations using simple respirometers to determine the effect of temperature on the rate of respiration
12.2.2 outline glycolysis as phosphorylation of glucose and the subsequent splitting of fructose 1,6-bisphosphate (6C) into two triose phosphate molecules (3C), which are then further oxidised to pyruvate (3C), with the production of ATP and reduced NAD
12.2.3 explain that, when oxygen is available, pyruvate enters mitochondria to take part in the link reaction
12.2.4 describe the link reaction, including the role of coenzyme A in the transfer of acetyl (2C) groups
12.2.5 outline the Krebs cycle, explaining that oxaloacetate (4C) acts as an acceptor of the 2C fragment from acetyl coenzyme A to form citrate (6C), which is converted back to oxaloacetate in a series of small steps
12.2.6 explain that reactions in the Krebs cycle involve decarboxylation and dehydrogenation and the reduction of the coenzymes NAD and FAD
12.2.7 describe the role of NAD and FAD in transferring hydrogen to carriers in the inner mitochondrial membrane
12.2.8.1 hydrogen atoms split into protons and energetic electrons
12.2.8.2 energetic electrons release energy as they pass through the electron transport chain (details of carriers are not expected)
12.2.8.3 the released energy is used to transfer protons across the inner mitochondrial membrane
12.2.8.4 protons return to the mitochondrial matrix by facilitated diffusion through ATP synthase, providing energy for ATP synthesis (details of ATP synthase are not expected)
12.2.8.5 oxygen acts as the final electron acceptor to form water
12.2.9 describe the relationship between the structure and function of mitochondria using diagrams and electron micrographs
15.1.1 describe the features of the endocrine system with reference to the hormones ADH, glucagon and insulin (see 14.1.8, 14.1.9 and 14.1.10)
15.1.10 describe the roles of neuromuscular junctions, the T-tubule system and sarcoplasmic reticulum in stimulating contraction in striated muscle
15.1.11 describe the ultrastructure of striated muscle with reference to sarcomere structure using electron micrographs and diagrams
15.1.12 explain the sliding filament model of muscular contraction including the roles of troponin, tropomyosin, calcium ions and ATP
15.1.2 compare the features of the nervous system and the endocrine system
15.1.3 describe the structure and function of a sensory neurone and a motor neurone and state that intermediate neurones connect sensory neurones and motor neurones
15.1.4 outline the role of sensory receptor cells in detecting stimuli and stimulating the transmission of impulses in sensory neurones
15.1.5 describe the sequence of events that results in an action potential in a sensory neurone, using a chemoreceptor cell in a human taste bud as an example
15.1.6 describe and explain changes to the membrane potential of neurones, including:
15.1.7 how the resting potential is maintained
15.1.8.1 how the resting potential is restored during the refractory period
15.1.8.2 describe and explain the rapid transmission of an impulse in a myelinated neurone with reference to saltatory conduction
15.1.8.3 explain the importance of the refractory period in determining the frequency of impulses
15.1.9 describe the structure of a cholinergic synapse and explain how it functions, including the role of calcium ions
Solution:
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