<span>#1) With reference to the role of oncogenes, explain how the normal controls over the cell cycle can be lost.
Answer: The way that cell cycle can be lost is by going through changes in the activity of cell cycle regulators. Cancer causes different types of mutations. There are two types of cell cycle regulators that can promote the development of cancer:
-Positive Regulators that can be over activated (become oncogenic).
-Negative Regulators (tumor suppressors) which can be inactivated.
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Answer:
The correct answer is -
1. right-handed
2. right-handed
3. positive
4. left-handed
5. negative
6. negative
Explanation:
In a circular bacterial chromosome, the structure of DNA is a right-handed double helix In a circular bacterial chromosome.
If DNA is twisted in the right-handed direction, it becomes overwound. Overwinding results in positive supercoiling takes place. If DNA is twisted in the left handd direction, it becomes underwound. Underwinding results in negative supercoiling.
f. One effect negative supercoiling in bacterial chromosomes is to promote separation of the two strands of DNA in the double helix
The answer for this should be D
Reactions that hydrolyze the phosphodiester bonds split the DNA molecule between the phosphate groups and the hydroxyl groups of the two sugar groups.
In DNA there is a covalent bond through a phosphate group that connects the hydroxyl group (OH) at the 5' position of the pentose sugar and the hydroxyl group at the 3' position of the pentose sugar of the next nucleotide. This covalent bond is called a phosphodiester bond because chemically the phosphate group is in the diester form.
In other words, the phosphodiester bond connects the sugar in one nucleotide to the sugar in the next nucleotide, so this bond simultaneously connects the two consecutive nucleotides to form a polynucleotide chain. If there is an enzyme that catalyzes the hydrolysis of covalent bonds that combine nucleotides, what happens is that the phosphodiester link between deoxyribose sugars will break.
Learn more about the phosphodiester bonds at brainly.com/question/23660733
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