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Cancer Chemotherapeutic Agents > Structure Of DNA > Flashcards

Structure Of DNA Flashcards

1
Q

What are the basic components of a nucleotide in DNA?

A

A nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine, thymine, guanine, or cytosine).

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2
Q

What is the structure of DNA?

A

DNA consists of two polynucleotide strands forming a double helix.

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3
Q

How do the nitrogenous bases pair in DNA?

A

Adenine pairs with thymine (A-T) via two hydrogen bonds, and guanine pairs with cytosine (G-C) via three hydrogen bonds.

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4
Q

What is the significance of major and minor grooves in DNA?

A

Major and minor grooves provide accessible sites for protein binding and drug interactions.

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5
Q

What role do alkylating agents play in cancer therapy?

A

Alkylating agents introduce modifications to DNA that prevent replication and transcription.

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6
Q

Fill in the blank: DNA is stabilized by _______ interactions and _______ bonds.

A

base-stacking; hydrogen

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7
Q

What is the primary structure of DNA?

A

The primary structure consists of a double helix formed by two antiparallel strands of nucleotides.

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8
Q

What are nitrogen mustards and how do they affect DNA?

A

Nitrogen mustards are alkylating agents that form aziridinium ions, causing cross-linking in DNA.

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9
Q

True or False: The B-DNA form has about 10 base pairs per turn.

A

True

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10
Q

What is supercoiling in DNA?

A

Supercoiling is the tertiary structure that allows DNA to be compacted for fitting within the cell nucleus.

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11
Q

What is the impact of alkylation on DNA structure?

A

Alkylation can lead to base mispairing, cross-linking, and DNA strand breaks.

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12
Q

What differentiates A-DNA from B-DNA?

A

A-DNA is more compact and dehydrated, while B-DNA is the most common form with accessible grooves.

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13
Q

What is the function of metal ions like Mg²⁺ in DNA?

A

Metal ions neutralize the negative charge of the phosphate backbone, enhancing stability.

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14
Q

Fill in the blank: The sugar-phosphate backbone of DNA is linked by _______ bonds.

A

phosphodiester

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15
Q

What are intercalating agents?

A

Intercalating agents are molecules that insert between DNA bases, potentially distorting its structure.

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16
Q

What is the role of transcription factors in DNA?

A

Transcription factors bind to major and minor grooves to regulate gene expression.

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17
Q

What is the mechanism of action of cisplatin?

A

Cisplatin forms adducts with the N7 position of guanine, leading to DNA bending and cross-linking.

18
Q

True or False: DNA’s structure is not affected by environmental factors.

A

False

19
Q

What are the three structural variants of DNA?

A

B-DNA, A-DNA, and Z-DNA.

20
Q

What is the significance of hydrogen bonding in DNA stability?

A

Hydrogen bonding between base pairs ensures the structural stability of the DNA double helix.

21
Q

What are the nucleophilic sites targeted by alkylating agents?

A

N7 of guanine, N3 of adenine, and O6 of guanine.

22
Q

What happens during DNA fragmentation?

A

DNA fragmentation can occur through hydrolytic reactions or repair enzyme actions on alkylated DNA.

23
Q

What is the structure of DNA?

A

DNA consists of two antiparallel polynucleotide strands coiled into a double helix

The strands run in opposite directions: 5’ to 3’ and 3’ to 5’.

24
Q

Which bases pair together in DNA and how many hydrogen bonds do they form?

A

Adenine (A) pairs with Thymine (T) via 2 hydrogen bonds, and Guanine (G) pairs with Cytosine (C) via 3 hydrogen bonds

This complementary base pairing is crucial for the stability of the DNA double helix.

25
Q

What are the major and minor grooves in DNA?

A

Grooves created by the helical structure of DNA that allow interaction with proteins and molecules

The major groove and minor groove are lined with hydrogen bond donors and acceptors.

26
Q

What is a nucleoside?

A

A nucleoside consists of a nitrogenous base attached to a deoxyribose sugar

Purines include adenine and guanine; pyrimidines include cytosine and thymine.

27
Q

What is a nucleotide?

A

A nucleotide is formed when one or more phosphate groups attach to a nucleoside

Nucleotides are the building blocks of DNA linked by phosphodiester bonds.

28
Q

What determines the genetic information encoded in DNA?

A

The sequence of nucleotides along a DNA strand

The order of bases forms the genetic code.

29
Q

What are the nucleophilic sites in DNA?

A

Mainly nitrogen and oxygen atoms in the bases

Nitrogen atoms involved in the nucleoside bonds are not available for reactions with electrophiles.

30
Q

What types of interactions govern nucleophile-electrophile attraction?

A

Electrostatic control and orbital control

These interactions influence the reactivity and bonding between nucleophiles and electrophiles.

31
Q

What is electrostatic control?

A

Attractive forces between oppositely charged particles

Involves the attraction between a negatively charged nucleophile and a positively charged electrophile.

32
Q

What is orbital control?

A

Overlap of molecular orbitals between a nucleophile and an electrophile

Facilitates the transfer of electrons and forms covalent bonds.

33
Q

What is the primary target for alkylating agents in DNA?

A

The N7 position of guanine

Other targets include nitrogen atoms in adenine, cytosine, and O6 of guanine.

34
Q

What impact does alkylation have on DNA?

A

Alkylation modifies DNA structure, disrupts hydrogen bonding, and leads to incorrect base pairing

This can prevent DNA replication and transcription.

35
Q

What are the consequences of DNA alkylation?

A

Inhibition of DNA functions, DNA cross-linking, and increased cytotoxicity

Cross-linking can stabilize DNA abnormally, blocking essential cellular processes.

36
Q

What is the mechanism of DNA alkylation by nitrogen mustards?

A

Formation of an aziridinium ion that reacts with nucleophilic sites on DNA

This disrupts the DNA double helix and prevents proper cellular function.

37
Q

Why are bifunctional alkylating agents more cytotoxic than monofunctional ones?

A

They can form multiple cross-links in DNA

There is a strong correlation between interstrand cross-linking and cytotoxic effect.

38
Q

What therapeutic implications do alkylating agents have?

A

Used in cancer chemotherapy to damage DNA and inhibit cancer cell proliferation

However, they can also affect normal cells, leading to side effects.

39
Q

True or False: The electrostatic attraction is influenced by the strength of the charges involved.

A

True

Stronger charges result in stronger electrostatic attraction.

40
Q

Fill in the blank: The aziridinium ion is a _______ intermediate in DNA alkylation.

A

reactive

It is key to the alkylation process.

Cancer Chemotherapeutic Agents (4 decks)

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