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Questions and Answers
Which component differentiates DNA from RNA?
What type of bonds are involved in joining nucleotides in a DNA strand?
Which base pair follows Watson-Crick base pairing rules?
According to Chargaff's rule, which statement is true regarding the bases in DNA?
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What is the structure formed by a nucleoside combined with three phosphate groups?
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What type of bonds hold the two strands of DNA together?
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In DNA, which of the following pairings is correct?
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What characterizes the structure of the DNA double helix?
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What happens to DNA during denaturation?
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According to Chargaff's rule, what is true for double-stranded DNA?
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What is the helical rise between DNA bases?
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What is the melting temperature (Tm) in the context of DNA?
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What feature of DNA describes the orientation of its strands?
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Study Notes
DNA Structure
- DNA is a polymer of nucleotides made up of a nitrogenous base, a phosphate group, and a pentose sugar (deoxyribose in DNA).
- RNA has ribose as its pentose sugar and uracil instead of thymine.
- Nucleosides comprise a sugar and a base.
- Nucleotides are formed by adding a phosphate group to a nucleoside.
- Adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP) are examples of nucleotides.
- Purines are double-ringed nitrogenous bases: Adenine (A) and Guanine (G).
- Pyrimidines are single-ringed nitrogenous bases: Cytosine (C), Thymine (T), and Uracil (U).
- Nucleotides are linked by 3’ → 5’ phosphodiester bonds.
- DNA is a double-stranded molecule with the two strands held together by hydrogen bonds through complementary base pairing.
- Guanine (G) pairs with Cytosine (C) via three hydrogen bonds.
- Adenine (A) pairs with Thymine (T) via two hydrogen bonds.
- DNA has two ends: the 3’ end, which has a hydroxyl group, and the 5’ end, which has a phosphate group.
- The two strands of DNA run in opposite directions, described as antiparallel.
- The DNA helix has two grooves: the major groove (wide) and the minor groove (narrow).
- Each turn of the DNA helix contains 10 base pairs and has a helical rise of 0.34 nanometers.
- DNA denaturation occurs when hydrogen bonds between base pairs are disrupted, causing the double helix to unwind.
- Denaturation can be caused by changes in pH or heat.
- Tm (Melting Temperature) is the temperature at which half of the helical structure is lost.
- A-T rich DNA denatures at lower temperatures compared to G-C rich DNA.
- The Chargaff’s rule states:
- The amount of Adenine (A) equals the amount of Thymine (T).
- The amount of Guanine (G) equals the amount of Cytosine (C).
- The total amount of purines (A + G) equals the amount of pyrimidines (T + C).
Factors Contributing to DNA Stability
- Hydrogen bonds between complementary base pairs.
- Hydrophobic interactions between stacked nitrogenous bases.
- Hydrophilic interactions between the sugar-phosphate backbone and the surrounding solution.
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Description
Test your knowledge on the structure of DNA with this quiz. Learn about the composition of nucleotides, the differences between DNA and RNA, and the base pairing rules. Perfect for students studying molecular biology or genetics.
