A1.2 Nucleic acidsIB Biology SL: Flashcards

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What is the genetic material of all living organisms?

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What is the genetic material of all living organisms?: DNA.
Why do RNA viruses not contradict 'DNA is the genetic material of all living organisms'?: Viruses are not considered to be living.
What are the three components of a nucleotide?: A phosphate group, a pentose sugar and a nitrogenous base.
How are nucleotides joined into a strand?: By condensation reactions forming covalent bonds between the phosphate of one nucleotide and the sugar of the next.
What is the sugar–phosphate backbone?: The continuous chain of covalently bonded sugars and phosphates forming the strong spine of each strand.
Name the bases of DNA and RNA.: DNA: adenine, thymine, guanine, cytosine. RNA: adenine, uracil, guanine, cytosine.
Which bases pair in DNA?: Adenine with thymine; guanine with cytosine.
What holds the two strands of DNA together?: Hydrogen bonds between complementary bases.
What does antiparallel mean?: The two strands run in opposite directions.
Give three differences between DNA and RNA.: DNA double-stranded, RNA single; DNA thymine, RNA uracil; DNA deoxyribose, RNA ribose.
How does deoxyribose differ from ribose?: Deoxyribose has one fewer oxygen: H instead of OH on carbon 2.
Why is complementary base pairing important?: It allows DNA to be replicated accurately and genetic information to be expressed.
How many sequences are possible for a DNA length of n bases?: 4ⁿ — so DNA has a limitless capacity to store information.
Why is the conserved genetic code evidence for common ancestry?: The same codons code for the same amino acids in almost all organisms, best explained by inheritance from a common ancestor.