A1.2 Nucleic acidsIB Biology HL: Flashcards

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What are the three parts of a nucleotide?

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What are the three parts of a nucleotide?: Phosphate, pentose sugar and nitrogenous base.
How do DNA and RNA differ?: DNA: two strands, thymine, deoxyribose. RNA: one strand, uracil, ribose.
Which bases pair in DNA and what bonds them?: A–T and G–C, by hydrogen bonds.
Why do RNA viruses not show that some living things use RNA?: Viruses are not considered living.
Why is the conserved genetic code evidence of common ancestry?: The same codons code for the same amino acids in almost all life.
HL: What are the 5' and 3' ends of a strand?: 5' end has a phosphate on carbon 5'; 3' end has a free OH on carbon 3'.
HL: In which direction are new nucleic acid strands built?: 5' to 3': nucleotides are added only to the 3' end.
HL: In which direction does a ribosome read mRNA?: 5' to 3'.
HL: Which bases are purines and which pyrimidines?: Purines: A, G. Pyrimidines: C, T, U.
HL: Why is DNA the same width regardless of sequence?: Each pair is a purine with a pyrimidine, so A–T and C–G pairs are equal in length.
HL: Describe a nucleosome.: DNA wrapped around eight histone proteins, held by an additional histone on the linker DNA.
HL: What did Hershey and Chase label, and with what?: Protein with ³⁵S and DNA with ³²P.
HL: What made the Hershey–Chase experiment possible?: The availability of radioisotopes as research tools.
HL: Which hypothesis did Chargaff's data falsify?: The tetranucleotide hypothesis (a repeating sequence of the four bases in equal amounts).
HL: How does falsification address the problem of induction?: Confirming observations can never prove a hypothesis, but one contradicting observation can reject it with certainty.