Bio Exam 2 - DNA Replication and PCR

Central dogma

DNA is transcribed into mRNA, DNA serves as the template for RNA, RNA is translated into proteins

Gene expression

Production of protein from instructions on the DNA

Steps to gene expression

Transcription, translation, folding of the protein into functional 3D form

2 main functions of DNA

storing genetic information and copying itself

Structure of a nucleic acid

Pentose sugar, phosphate group, nitrogenous base

Which carbons do the phosphate, hydroxyl group, and base attach to

phosphate attaches to 5’, hydroxyl group attaches to 3’, base attaches to 1’

How many hydrogen bonds do A and T form; How many hydrogen bonds do C and G form

2; 3

Bases for DNA; Bases for RNA

ATCG; AUCG

Difference between deoxyribose and ribose

Deoxyribose has one hydroxyl group at 3’; ribose has two hydroxyl groups at 2’ and 3’

DNA replication is semiconservative

the double helix will split in 2, and each strand is used as a template for the new strand; half the DNA is from the original, and half the DNA is new

Parental strands; Daughter strands

template; new strand

Which bonds are broken when DNA is replicated

Hydrogen bonds holding the base pairs together

Site where DNA is locally opened

replication fork

Enzymes in DNA replication

Helicase, DNA binding proteins, primase, DNA polymerase 3, exonuclease, ligase

Helicase

Unwinds parental double helix

DNA binding proteins

keep the strands separated, prevent them from rewinding

Primase

adds RNA primer to template strand

DNA polymerase 3

adds nucleotides to the RNA primer and proofreads

Exonuclease/DNA polymerase 1

removes RNA primers and inserts correct bases/replaces the nucleotides

Ligase

joins okazaki fragments together and seals nicks in sugar-phosphate backbone/forms bonds

Topoisomerase

Relieves tension on the double helix

Order the enzymes work in

helicase, primase, DNA polymerase, ligase

What direction does replication occur

5’ to 3’

Leading strand vs Lagging strand

Leading - continuous, lagging - okazaki fragments

How do you know which strand will be the leading strand and which will be the lagging strand

Leading strand will be going the same direction as the fork opens, lagging will go the opposite direction

Proofreading

DNA polymerase removes and replaces incorrect nucleotides, it recognizes if the bases are paired correctly

PCR

method in which multiple repetitions of DNA replication are performed in a test tube

What do you need for PCR

DNA template, primers, nucleotides, DNA polymerase bacteria

PCR steps

Denaturation - DNA template is denatured with high heat to separate strands; annealing - DNA primers bind to the template DNA; extension - DNA polymerase creates a new strand of DNA complementary to the template DNA starting from the primer; repeated many times