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you could describe the mechanism of drugs such as the statins, which inhibit the function of the enzyme HMG-CoA reductase and so reduce the synthesis of cholesterol in the body. You could report the manner in which the inhibitors interact with their enzyme target, if they are allosteric or competitive and what the result of that inhibition is to the cell. (Try to pick an alternative example to statins).
Assess the possibility of errors occurring during the stages of protein synthesis, particularly during transcription and translation. Analyse the cause and effect of genetic mutations in DNA, including:
• Missense
• Nonsense
• Silent
• Insertion
• Deletion
• Duplication
• frameshift
Provide examples of the impact that these errors may have on the end products of protein synthesis.
Discuss how the genetic code allows proteins to be synthesised with minimal errors taking place, including:
• triplet codes
• codon
• anticodon
• degenerate code
• non-overlapping
3) Chemical elements of tobacco smoke can change the nucleotide sequence in a DNA molecule by
replacing adenine with thymine or guanine with cytosine. Which kind of mutation is this one? Draw and
explain the mechanisms and consequences of such a change.
1) A.I., a 6-year-old boy, is undergoing examination due to a slight developmental delay. He has
difficulty climbing stairs, running, has reduced physical strength and low endurance during intense physical
exercise. Muscle biopsy results showed a pronounced change in muscle fiber size.
Based on these results, the child has a preliminary diagnosis of having Duchene muscular dystrophy
(DMD). Duchene muscular dystrophy is a serious recessive disease linked to the X chromosome, which is
characterized by the rapid progression of muscular dystrophy, which ultimately leads to a complete loss of
the patient’s ability to move and consequent death.
To confirm diagnosis and determine the mutation in the dystrophic gene in A.I, DNA diagnostics
were performed. Aberrations were found in the coding part of the gene
Questions for discussion:
1. What type of mutation causes Duchene muscular dystrophy?
2. Describe the mechanism of mutation occurrence. What are the consequences of this mutation?
3. Determine the genotypes of parents and the patient.
4. Determine the risks for the next child to have the same illness.
2) After being in a solarium, a woman found an increase in the number of neoplasms on her skin. The cause
of the neoplasm was a violation of the nucleotide sequence due to exposure to UV rays.
1. What changes in the DNA molecule occur under the influence of UV radiation?
2. What type of repairation corrects such damage? Schematic depict and explain.
1) A large number of DNA disorders occur in human cells. Up to 10,000 DNA damage can be recorded
daily in our body. However, the action of genetic homeostasis mechanisms allows maintaining the relative
constancy of the cell genotype.
1. What do you know about the main ways to maintain genetic cell homeostasis? What are they
characterized by?
2. In what phases of the mitotic cycle can DNA damage be corrected?
3. What environmental factors can lead to genetic disorders?
4. What are the consequences of genotype violations in somatic cells if they are not corrected?
4) When so much damage occurs in DNA that during excision reparation the cell does not have time to
completely eliminate them. As a result, after replication of this DNA the daughter chain has “gaps” that are
formed at the site of damage of the mother DNA chain,.
1. What type of reparation corrects such damage?
2. What are the molecular mechanisms the cause of this disorder?
3. Feature of postreplication reparation.
4. What other types of postreplication reparation do you know, describe.
3) A 3-year-old boy, was sent to a dermatology clinic due to a pronounced sensitivity to sunlight and the
appearance of multiple skin spots. Clinical examination revealed photophobia, conjunctivitis and significant
lentiginous hyperpigmentation of unprotected from the sun skin surface; otherwise, its development and
inspection data were normal. Child-patient is from an unrelated marriage.
The dermatologist said that the child has a classic manifestation of pigment xerodermia. To confirm the
diagnosis, a skin biopsy was performed to evaluate DNA reparation. The results of this test confirmed the
diagnosis of pigment xerodermia. Despite appropriate preventive measures, at the age of 15 the child got
metastatic melanoma and died after 2 years. His parents have two other children; no one of them is sick
with pigment xerodermia.
Issues for discussion:
1. What type of reparation is knocked out by pigment xerodermia?
2. What are the molecular mechanisms of reparation of this disorder?
3. Determine the genotypes of parents, all children.
4. Calculate the risk of having sick children in this family.
5. Make a comparative characteristic with photoreactivation.
1. A DNA fragment encoding a polypeptide has a following order of nitrogenous bases:
AAAACCAAAATACTTATACAA. During replication, the third adenine on the left was cut from the
chain. Determine the structure of the polypeptide chain encoded by this DNA region according to normal
and mutated condition. Identify the type of gene mutation.
