BIOCHEM C785 Kaleys Comprehensive Study Guide Final. Complete. Latest Update 2022.DNA = phosphate + deoxyribose sugar + A/T/C/G
o Contains two strands.
... [Show More] The strands are antiparallel (opposite each other).
o 5’ → 3’
3’ ← 5’
RNA = phosphate + ribose sugar + A/U/C/G
o Single strand, can fold back onto itself and form pairs between itself (stem‐loop).
Each nucleic acid is made up of polymers (many monomers) that are called nucleotides.
o Nucleotides contain one or more phosphates, a five‐carbon sugar, and a nitrogen base.
o Nucleotides are always made in the 5’ to 3’ direction.
o 5 is always the beginning of the strand, 3 is the end where nucleotides are added.
DNA organization: DNA is wrapped around proteins called histones → nucleosome → chromaƟn fiber→
chromosomes
Steps to the central dogma:
o Coding DNA → template DNA → mRNA → tRNA (amino acid)
o DNA → transcribed to mRNA → translated to protein
o Each step is complementary (opposite) to the previous step, but if you skip a step it will be identical to
the previous step.
o Example
1. Coding DNA strand 5’ AAA TTT GGG CCC 3’
2. Template DNA strand 3’ TTT AAA CCC GGG 5’
3. mRNA 5’ AAA UUU GGG CCC 3’
4. tRNA Lys Phe Gly Pro
Pairing:
o DNA: A → T
o RNA: A → U
DNA replication:
o Because DNA is a double helix, one strand can be separated and serve as a template for synthesis of a
new strand.
o Semi‐conservative: each copy of DNA contains a template strand and a new strand.
o Steps of replication:Page 2 of 39
o 1. The DNA must be separated, creating a replication fork. This is done by helicase.
o 2. Primase attaches an RNA primer, where the replication is to start.
o 3. DNA polymerase adds bases to the remaining of the strand until it reaches a stop codon. This
is done in fragments, called okazaki fragments.
If an error is detected, it removes the nucleotides and replaces them with correct ones,
known as exonuclease.
o Exonuclease removes all of the RNA primers, and DNA polymerase fills in those gaps.
o DNA ligase seals the two strands forming a double helix.
DNA → transcribed → mRNA → translated → protein [Show Less]