Molecular Basis of Inheritance — Flashcards
Punjab Board · Class 12 · Biology
33 flashcards for Molecular Basis of Inheritance (Punjab Board Class 12 Biology) to test yourself on key terms and facts.
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What is a nucleotide and what are its three main components?
Answer
A nucleotide is the basic building block of nucleic acids. Its three main components are: (1) A nitrogenous base (either purine: Adenine/Guanine, or pyrimidine: Cytosine/Thymine/Uracil), (2) A pentose…
What does the double helix structure of DNA look like and what are its five salient features?
Answer
The DNA double helix is a twisted ladder-like structure. Its five salient features are: (1) Made of two polynucleotide chains with sugar-phosphate backbones and bases projecting inward, (2) The two ch…
Why does the distance between two polynucleotide chains in DNA remain almost constant?
Answer
The distance between the two polynucleotide chains remains approximately constant (~1.1 nm) because of Chargaff's rule and base pairing specificity. Purines (Adenine and Guanine) are larger, two-ringe…
How is DNA packaged into the nucleus when the DNA length far exceeds the nuclear dimensions?
Answer
DNA is packaged through a hierarchical process: (1) DNA wraps around histone octamers (8 histone proteins rich in lysine and arginine) to form nucleosomes, each containing ~200 bp of DNA, (2) Nucleoso…
What was Griffith's 'Transforming Principle' experiment and what did it demonstrate?
Answer
In 1928, Frederick Griffith worked with Streptococcus pneumoniae bacteria. He observed that: (1) S strain (smooth, with mucous coat) was virulent; R strain (rough, no coat) was non-virulent, (2) Heat-…
How did Avery, MacLeod, and McCarty prove that DNA is the transforming principle?
Answer
Avery, MacLeod, and McCarty (1933-44) purified different biochemicals (proteins, DNA, RNA, etc.) from heat-killed S strain cells and tested which could transform R strain to S strain. They found that:…
Describe the Hershey-Chase experiment and explain how it proved DNA is the genetic material.
Answer
Hershey and Chase (1952) worked with bacteriophages (viruses that infect bacteria). Their methodology: (1) Grew viruses in medium with radioactive phosphorus (³²P) - incorporated into DNA but not prot…
What are the key chemical differences between DNA and RNA, and why does this make DNA a better genetic material?
Answer
Key chemical differences: (1) DNA contains deoxyribose sugar; RNA contains ribose sugar, (2) DNA has thymine; RNA has uracil in its place, (3) DNA is usually double-stranded; RNA is usually single-str…
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