midterm-2-deferred-bio-1140-2022

4. Which of the following corresponds to the lowest level of organisation of the genetic material? A. A replicated chromosome B. A nucleosome C. A chromatid D. A scaffolded chromatin E. A set of 46 chromosomes Answer: B Explanation: The levels of organisation are as follow (from lowest to highest): 1. Nucleosome 2. Scaffolded chromatin 3. Chromatid 4. Replicated chromosome 5. Set of 46 chromosomes 5. Consider meiotic division. In which phase can homologous chromosomes separate into different combinations? A. Metaphase II B. Interphase C. Anaphase II D. Anaphase I E. Prophase Answer: D Explanation: Inter‐chromosomal recombination occurs during anaphase I, in which homologous chromosomes are split equally between the two poles of the cell. This gives different possible combinations (assortments) of homologous chromosomes to form a complete set. 6. A cell has a very low cytosolic concentration of glucose. Which checkpoint will ensure that the cell cycle is stopped until the glucose concentration is high enough? A. The G 0 checkpoint B. The G 1 checkpoint C. The G 2 checkpoint D. The M checkpoint E. The interphase checkpoint Answer: B Explanation: The G 1 checkpoint ensures that there is enough resource for the cell to proceed with the rest of the cell cycle. This includes glucose, used to produce ATP (necessary to provide energy for cell division). Downloaded by Zackary Mulligan (zackmulligan99@gmail.com) lOMoARcPSD|28339034

2. A bacteria parental cell containing the following sequence has divided into two daughter cells. Briefly explain what happened in the parental cell. Name one mechanism that has failed and briefly explain its consequence. ( 2 marks ) Answer:  A base pair mismatch has occurred during replication ( 0.5 mark ), with a T being replaced by a C ( 0.5 mark ).  The mismatch/DNA repair mechanism/proofreading/nucleotide excision/nuclease activity has failed ( 0.5 mark ) and this led to a permanent mutation in daughter cell 2 (since bacteria are unicellular organisms) ( 0.5 mark ). 3. Thermophilic bacteria have a genome with high GC content (i.e. high percentage of guanine and cytosine) Explain the effect of high GC content on the DNA molecule and what consequence this has on these bacteria. ( 2 marks ) Answer:  Effect: in double stranded DNA molecules, guanine and cytosine are paired with 3 hydrogen bonds (Concept 1 ‐ 1 mark ).  Consequence: More hydrogen bonds makes the genome of thermophilic bacteria (that live in high temperature) more stable (at high temperature) (accepted: the two strands do not separate or are not denatured as much at high temperature) (Concept 2 ‐ 1 mark ). Mentioning that the genome of bacteria that live at high temperature is more adapted to those conditions without mentioning the idea of stability is worth 0.5 mark. 4. Name a DNA dependent‐RNA polymerase that intervenes in replication. What would happen if such polymerase was not functional? ( 2 marks ) Answer:  The primase is a DNA dependent‐RNA polymerase that intervenes in replication (Concept 1 ‐ 1 mark ).  If the primase was not functional, primers would not be placed on either the leading or lagging strand, which would result in the inability of the DNA polymerase III to synthesize either strand. (Concept 2 ‐ 1 mark ). Mentioning that replication would not occur, without referring to a specific mechanism is worth 0.5 mark. Downloaded by Zackary Mulligan (zackmulligan99@gmail.com) lOMoARcPSD|28339034