Podcast
Questions and Answers
What is the term used for the area in DNA containing the same sequence of bases repeated several times in tandem?
What is the term used for the area in DNA containing the same sequence of bases repeated several times in tandem?
Which type of DNA is known for having hypervariable repeat units and is specifically used in DNA fingerprinting?
Which type of DNA is known for having hypervariable repeat units and is specifically used in DNA fingerprinting?
What are the two categories based on the number of base pairs in repetitive DNA?
What are the two categories based on the number of base pairs in repetitive DNA?
Which nitrogen base is complementary to adenine in RNA?
Which nitrogen base is complementary to adenine in RNA?
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What type of viruses contain RNA as their genetic material?
What type of viruses contain RNA as their genetic material?
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Which component of RNA is represented by the pentose sugar called ribose?
Which component of RNA is represented by the pentose sugar called ribose?
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What type of DNA sequences do restriction endonucleases commonly recognize?
What type of DNA sequences do restriction endonucleases commonly recognize?
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Study Notes
DNA Structure
- Two chains are joined by weak hydrogen bonds, with specific pairing: A = T, G = C.
- The H atom of one base is linked to the O2 or N2 atom of another base.
- The two strands are antiparallel, with 3' and 5' phosphor links in opposite directions.
- The pairing is specific, and the sequence of N2 bases in one chain determines the sequence in the other chain.
- The diameter of DNA is 20 A°.
Erwin Chargaff's Rule
- Regardless of the source, purine and pyrimidine components occur in equal amounts in a DNA molecule.
- This rule is based on the following relationships:
- A = T, G = C
- A + C = T + G
- A + G = T + C
- A + T ≠ G + C (not always true)
James Watson and Francis Crick's Model
- The model is based on X-ray crystallography technique.
- DNA consists of two right-handed helices.
- Each turn has 10 nitrogen base pairs.
- One spiral has a length of 3.4 A°.
- The distance between two nitrogen bases is 3.4 A°.
Denaturation and Renaturation of DNA
- Denaturation: When DNA solution is heated or exposed to alkaline or acidic pH, H bonds break, and the two strands uncoil.
- Renaturation: When the solution is gradually cooled or neutralized, new base pair formation begins, and the double-stranded DNA is formed.
DNA Types
- Linear DNA with free ends (eukaryotes) has histones.
- Circular DNA with covalently linked ends (prokaryotes) has no histones.
Properties of Proteins
- There are thousands of proteins, varying in length, number, and type of polypeptides.
- Proteins have high specificity in individuals but are shared with related species or groups.
- Molecular weight ranges from 4,500 daltons (ACTH) to 4,600,000 daltons (Pyruvate Dehydrogenase).
- Solubility: Some proteins are insoluble due to large size, while many form colloidal solutions with water.
- Amphoteric nature: Proteins show both acidic and basic properties.
- Electrical reaction: Proteins have an isoelectric point at which pH is neutral.
- Denaturation: Proteins can undergo permanent or temporary loss of three-dimensional structure due to UV, heat, strong acid, and alkali, or high salt concentration.
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Description
Test your knowledge on the structure of DNA and the concept of complementary base pairing. Learn about the specific hydrogen bonding between adenine-thymine and guanine-cytosine. Explore topics like the anti-parallel nature of DNA strands and Erwin Chargaff's rule.
