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C785 Kaleys_Comprehensive_Study_Guide_final 2021/2022 | Biochem_Kaleys_Comprehensive_Study_Guide_final _ Graded A

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Biochemistry: Mod 1  DNA = phosphate + deoxyribose sugar + A/T/C/G o Contains two strands. 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 → chromatin 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 1 of 41 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  Transcription occurs in the nucleus: o Initiation: RNA polymerase binds to a sequence of DNA called the promoter, found near the beginning of a gene. Each gene has its own promoter. Once bound, RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription. Page 2 of 41 o Elongation: One strand of DNA, the template strand, acts as a template for RNA polymerase. As it "reads" this template one base at a time, the polymerase builds an RNA molecule out of complementary nucleotides, making a chain that grows from 5' to 3'. The RNA transcript carries the same information as the non-template (coding) strand of DNA, but it contains the base uracil (U) instead of thymine (T). [Show More]

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