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what is a nucleotide made up of?
a sugar, a phosphate group, and a base
what is the structure of DNA?
double helix polymer made up of repeating nucleotides bound covalently, and linked by phosphodiester bonds
hydrogen bonds
connect complementary DNA strands (A, T, G, C)
pyrimidines
cytosine and thymine
purines
guanine and adenine
how many chromosomes are in eukaryotic cells?
multiple
how many chromosomes are in prokaryotic cells?
one circular chromosome
where are chromosomes located in eukaryotic cells?
the nucleus
where are chromosomes located in prokaryotic cells?
the nucleoid
the two strands of DNA are ___
complementary, meaning the sequences of bases on one strand can be used to create the correct sequence of bases in the other strand
semiconservative replication
produces two new copies of double stranded DNA that each contain one of the original strands of DNA and one new strand
what are the main stages of DNA replication?
initiation, elongation, termination
replication fork
region where a cell’s double helix DNA has been unwound and separated to create an area for replication
helicase
enzymes that “unzip the DNA” and separate the two strands of the double helix to allow access for other enzymes involved in DNA replication
RNA primer
RNA molecules that are used to initiate DNA synthesis during replication
DNA polymerase (DNAP)
type of enzyme that create DNA molecules by assembling nucleotides
okazaki fragments
short, newly made DNA fragments that are formed on the lagging template strand during DNA replication
what is the leading strand?
the DNA strand that runs in the 5’ to 3’ direction in the replication fork; it is made as a continuous piece
what is the lagging strand?
the DNA strand that runs in the 3’ to 5’ direction towards the replication fork, also holds okazaki fragments
DNA ligases
enzymes needed for DNA repair, replication, and recombination
mistakes during replication are detected and repaired by ___
DNA polymerase
mismatch repair
functions to correct replication errors in newly made DNA, and to prevent recombination between related, but not identical DNA sequences
nucleotide excision repair (NER)
removes lesions on the DNA caused by UV radiation or chemical damage
uncorrected replication errors result in ___
mutations
what are three different categories of mutations?
point, frameshift, and chromosome
what is telomerase?
an enzyme in cells that helps keep them alive by adding DNA to telomeres (the ends of chromosomes)
what does transcription do?
converts DNA into messenger RNA (mRNA)
what does translation do?
decodes mRNA into amino acids
where does transcription occur?
in the nucleus
where does translation occur?
in the ribosome
what are the three types of RNA?
messenger, ribosomal, and transfer
what does messenger RNA do?
carries protein info from the DNA in the nucleus to the cytoplasm
what does ribosomal RNA do?
decodes amino acids and links them together
what does transfer RNA do?
serves as a link between the messenger RNA and the growing chain of amino acids that make up a protein
what happens during initiation of transcription?
RNA polymerase binds to the promoter region of a gene
what happens during elongation of transcription?
RNA polymerase adds nucleotides to the strand according to the base pairing
what happens during termination of transcription?
RNA polymerase reaches the end of the DNA strand and detaches
elongation occurs at a rate of __ nucleotides per second
40
what happens during initiation of translation?
the first tRNA, mRNA, and ribosome get together
what happens during elongation of translation?
the amino acid chain gets longer
what happens during termination of translation?
a stop codon reaches the ribosome’s A site and mRNA leaves the ribosome
every three bases (a triplet) specifies an __ to be included into a growing polypeptide chain
amino acid
each base triplet in RNA is called a ___
codon
what is the “start” codon?
AUG
eukaryotic gene expression is regulated during ___, ___, and ___
transcription and RNA processing, protein translation, and post-translational modifications of proteins
Note 
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