Molecular Basis of Inheritance and DNA Structure

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Questions and Answers

Which of the following are components of a nucleotide?

  • Nitrogenous base
  • Pentose sugar
  • Phosphate group
  • All of the above (correct)

What is the genetic material for the majority of organisms?

DNA

What type of sugar is present in RNA?

  • Deoxyribose
  • Fructose
  • Ribose (correct)
  • Glucose

What are the two types of nitrogenous bases?

<p>Purines and Pyrimidines</p> Signup and view all the answers

Thymine is present in RNA.

<p>False (B)</p> Signup and view all the answers

What linkage forms a nucleoside from a nitrogenous base and a pentose sugar?

<p>N-glycosidic linkage</p> Signup and view all the answers

The haploid content of human DNA is approximately ______ base pairs.

<p>3.3 × 10^9</p> Signup and view all the answers

What is the linkage called that connects two nucleotides in a DNA molecule?

<p>3'-5' phosphodiester linkage (A)</p> Signup and view all the answers

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Study Notes

Molecular Basis of Inheritance

  • DNA is identified as the primary genetic material in most organisms, with RNA also serving a genetic role in some viruses.
  • DNA's structure involves long polymers of deoxyribonucleotides, characterized by the number of nucleotide pairs, also known as base pairs.
  • Specific examples of DNA length include:
    • Bacteriophage φ ×174: 5386 nucleotides
    • Bacteriophage lambda: 48,502 base pairs
    • Escherichia coli: 4.6 million base pairs
    • Human haploid DNA: 3.3 billion base pairs

Structure of DNA

  • Each nucleotide comprises three components:

    • A nitrogenous base (purines: Adenine, Guanine; pyrimidines: Cytosine, Thymine in DNA, Uracil in RNA)
    • A pentose sugar (deoxyribose in DNA, ribose in RNA)
    • A phosphate group
  • Nitrogenous bases link to the 1' carbon of the pentose sugar via N-glycosidic bonds, forming nucleosides (e.g., adenosine, guanosine).

  • When a phosphate group is attached to the 5' carbon of a nucleoside through a phosphoester bond, a nucleotide is formed.

Formation of Polynucleotide Chains

  • Nucleotides are joined by 3'-5' phosphodiester linkages, creating dinucleotides and longer polynucleotide chains.
  • Each polynucleotide chain has a defined orientation with:
    • A free phosphate group at the 5' end
    • A free hydroxyl group at the 3' end

Transcription and Translation

  • Replication of DNA leads to transcription, where RNA is synthesized from DNA templates.
  • The genetic code derived from DNA determines the sequence of amino acids in proteins through translation.

Human Genome Project

  • Recent developments in genomics, including comprehensive sequencing of the human genome, have significant implications for genetics and biotechnology.

RNA Functions

  • In addition to acting as the genetic material in some viruses, RNA serves multiple roles:
    • Messenger RNA (mRNA): carries genetic information.
    • Adapter and structural roles in protein synthesis.
    • Some RNA molecules exhibit catalytic properties.

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