Review sheet – Chapter 10

Know the 4 types of nucleotides that make up DNA and RNA

Understand that DNA and RNA are nucleic acids consisting of polynucleotides (long chains of
nucleotides)

Know that DNA exists as a double helix and has 2 sugar-phosphate backbones that each run in
opposite directions of the other (5’ to 3’, and 3’ to 5’)

Understand that the nitrogenous bases of a DNA molecule pair specifically (A-T, C-G); be able to
describe what the complimentary strand of DNA would be if given the other strand

Understand that DNA replication occurs on both strands, with the old (parental strand) serving
as a template for the new (daughter) strand being laid down (synthesized), resulting in 2
complete DNA molecules, each consisting of a double helix of a parental and daughter strand

Know that the enzymes that link DNA nucleotides to a growing daughter strand are called DNA
polymerases and that DNA polymerase adds nucleotides only to the 3’ end, never to the 5’ end,
so a new strand ‘grows’ from 5’ to 3’

Understand that DNA polymerase attaches to both strands of the DNA molecule and that
replication proceeds continuously from the 3’ end, but must be synthesized in pieces from the 5’
end (since the polymerase attaches only to the 3’ end)

Understand that the pieces of DNA being synthesized are linked together by the enzyme, DNA
ligase

Understand that DNA polymerases carry out proof-reading steps to remove any nucleotides
paired incorrectly, and that DNA polymerases and ligases are involved in repairing damaged
DNA

Remember that DNA replication occurs during the interphase stage of the cell cycle

Understand the central dogma of molecular biology; that DNA is transcribed into RNA which is
then translated into proteins

Know that DNA transcription occurs in the nucleus (in eukaryotic organisms) and that RNA
translation occurs in the cytoplasm (at a ribosome)

Know that a gene may consist of hundreds or thousands of nucleotides

Know that transcription is the act of rewriting the code of DNA into messanger RNA

Know that messenger RNA contains a triplet code, written in a series of 3-base ‘words’ called
codons

Understand that the genetic code is a set of instructions indicating which codons (3-base
sequences) are translated into which amino acid

Understand that for each of the 20 amino acids, there are 1-4 codons which code exclusively for
them (Met has only 1, the others have 2-4)

Know that the codon AUG acts as a “start” signal and also codes for the amino acid methionine

Know that there are 3 codons that signal as a “stop” signal – these are UAA, UAG, UGA – you do
not need to know these, but be able to tell the difference between a ‘stop’ and a ‘start’ codon

Know that the genetic code is nearly universal, thus the same codons code for the same amino
acids in nearly all organisms (including bacteria)

Know that the enzyme RNA polymerase attaches to an area on the DNA molecule (1 strand only)
and reads the DNA molecule, selecting the appropriate nucleotide to build the messenger RNA
molecule

Know that before the newly synthesized mRNA strand leaves the nucleus, it first receives a cap
and a tail to protect the genetic code and facilitate it leaving the nucleus, and also know that
introns are removed from the mRNA molecule

Know that introns are the intervening sequences of DNA which do not code for any amino acid,
whereas exons are the coding regions of DNA which remain and will code for specific amino
acids

Understand that transfer RNA is the molecule that recognizes the codons in the mRNA molecule
via its own anticodons and binds to the amino acid that is specific to that anticodon

Understand that there is a specific transfer RNA molecule for each amino acid

Understand that transfer RNA molecules take the information of the messenger RNA molecule
and builds a polypeptide by laying down the appropriate amino acid one by one; this process is
called translation and occurs at a ribosome in the cytoplasm

Understand that a ribosome contains binding sites for both messenger RNA and transfer RNA

Be able to describe which RNA has codons (messenger RNA) and which has anticodons (transfer
RNA)

Understand that your professor is in love with Hugh Jackman

Know what a mutation is; understand that a change in a single nucleotide can result in a
mutation, and that insertions and deletions of nucleotides are the most harmful

Know that a mutagen is an agent that causes mutations, but that mutations may also be caused
spontaneously during DNA replication

Know that a virus is an infectious fragment of nucleic acid surrounded by a protein coat, and
understand that they may be contain either RNA or DNA

Know that viruses infect virtually every living organism on the Earth

Be able to describe the difference between the lytic and lysogenic cycles of a virus