Molecular Basis OF Inheritance flash cards

1. 1.What is the genetic material in most living organisms?

   DNA (Deoxyribonucleic acid). In some viruses RNA is the genetic material.

   Hint: Nucleic acid

2. 2.Name the two types of nucleic acids.

   DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

   Hint: D and R

3. 3.What are the three components of a nucleotide?

   A nitrogenous base, a pentose sugar (deoxyribose in DNA, ribose in RNA), and a phosphate group.

   Hint: Base + sugar + phosphate

4. 4.Name the two purines found in DNA.

   Adenine (A) and Guanine (G). Purines are double-ringed.

   Hint: Pure As Gold; double ring

5. 5.Name the pyrimidines in DNA and RNA.

   DNA: Cytosine (C) and Thymine (T). RNA: Cytosine (C) and Uracil (U). Pyrimidines are single-ringed.

   Hint: CUT the pie; single ring

6. 6.What is a nucleoside?

   A nitrogenous base linked to a pentose sugar (base + sugar), without the phosphate. Examples: adenosine, guanosine, cytidine, uridine.

   Hint: No phosphate

7. 7.What bond joins the phosphate to the sugar between adjacent nucleotides?

   A phosphodiester bond (3'-5' phosphodiester linkage) forms the sugar-phosphate backbone.

   Hint: 3'-5' linkage

8. 8.Which base pairs with which in DNA, and by how many hydrogen bonds?

   Adenine pairs with Thymine (2 H-bonds); Guanine pairs with Cytosine (3 H-bonds). This is complementary base pairing (Chargaff).

   Hint: A=T, G≡C

9. 9.State Chargaff's rule.

   In double-stranded DNA, the amount of Adenine = Thymine and Guanine = Cytosine; thus purines = pyrimidines (A+G = T+C).

   Hint: A=T, G=C

10. 10.Who proposed the double helix model of DNA and in which year?

    James Watson and Francis Crick (1953), based on X-ray diffraction data of Maurice Wilkins and Rosalind Franklin.

    Hint: 1953

11. 11.What is the nature of the two strands in the DNA double helix?

    Antiparallel — one strand runs 5'→3' and the other runs 3'→5'.

    Hint: Opposite polarity

12. 12.What is the pitch (distance of one turn) of the B-DNA helix and how many base pairs per turn?

    Pitch = 3.4 nm (34 Å) per turn, with about 10 base pairs per turn; distance between adjacent base pairs = 0.34 nm.

    Hint: 3.4 nm, 10 bp

13. 13.What is the diameter of the DNA double helix?

    About 2 nm (20 Å).

    Hint: 2 nm

14. 14.In which direction does the DNA double helix coil (B-form)?

    Right-handed helix.

    Hint: Right-handed

15. 15.What holds the two strands of DNA together?

    Hydrogen bonds between complementary base pairs, and base stacking interactions provide additional stability.

    Hint: H-bonds

16. 16.Calculate the length of E. coli DNA with 4.6 × 10^6 bp (distance per bp = 0.34 nm).

    Length = 4.6 × 10^6 × 0.34 × 10^-9 m ≈ 1.36 × 10^-3 m (about 1.36 mm).

    Hint: bp × 0.34 nm

17. 17.Approximately how many base pairs make up the human (haploid) genome?

    About 6.6 × 10^9 bp in a diploid cell (~3.3 × 10^9 bp haploid); total length ~2.2 metres.

    Hint: ~6.6 × 10^9 bp

18. 18.What is a histone octamer and what is its charge?

    Eight histone proteins (two each of H2A, H2B, H3, H4). Histones are positively charged (rich in basic amino acids lysine and arginine).

    Hint: 8 histones, positive

19. 19.What is a nucleosome?

    The basic unit of chromatin — negatively charged DNA (about 200 bp) wrapped around a positively charged histone octamer.

    Hint: DNA + histone octamer

20. 20.What is chromatin?

    The thread-like stained, packaged structure of nucleosomes (repeating units) in the nucleus; 'beads-on-string' under electron microscope.

    Hint: Beads on a string

21. 21.Which histone is involved in packaging nucleosomes into higher order structures (30 nm fiber)?

    Histone H1 (linker histone), which lies outside the core and seals the DNA at the entry/exit points.

    Hint: H1 linker

22. 22.Differentiate euchromatin and heterochromatin.

    Euchromatin: loosely packed, lightly stained, transcriptionally active. Heterochromatin: densely packed, darkly stained, transcriptionally inactive.

    Hint: Loose active vs dense inactive

23. 23.What are NHC proteins?

    Non-histone chromosomal proteins — additional proteins required for packaging chromatin at higher levels beyond nucleosomes.

    Hint: Higher-order packaging

24. 24.Who conducted the transformation experiment and with which organism?

    Frederick Griffith (1928), using Streptococcus pneumoniae (Diplococcus) in mice.

    Hint: Griffith, 1928

25. 25.What are the two strains of Streptococcus pneumoniae in Griffith's experiment?

    S strain (smooth, virulent, has polysaccharide capsule) and R strain (rough, non-virulent, no capsule).

    Hint: S = smooth/virulent

26. 26.What did Griffith observe with heat-killed S + live R strain in mice?

    The mice died. Live R bacteria had been 'transformed' by heat-killed S bacteria into virulent S-type; live S bacteria were recovered.

    Hint: Transformation

27. 27.What did Griffith conclude from his transformation experiment?

    Some 'transforming principle' from the heat-killed S strain transferred to the R strain, but he could not identify its biochemical nature.

    Hint: Transforming principle

28. 28.Who biochemically identified the transforming principle and what did they conclude?

    Oswald Avery, Colin MacLeod and Maclyn McCarty (1933-44); they showed DNA (not protein or RNA) was the transforming principle.

    Hint: Avery-MacLeod-McCarty; DNA

29. 29.In the Avery-MacLeod-McCarty experiment, what did protease and RNase digestion show?

    Digestion by proteases and RNases did NOT stop transformation, but digestion by DNase did — proving DNA is the transforming (genetic) material.

    Hint: DNase stops it

30. 30.Who performed the bacteriophage experiment and in which year?

    Alfred Hershey and Martha Chase (1952), using bacteriophage T2 infecting E. coli.

    Hint: Hershey-Chase, 1952

Open the interactive deck for the other 77 cards, with self-grading so the ones you keep missing come back.