DNA Replication Flashcards
Nucleus
Contains DNA
Nuclear membrane
Continuous with ER
Nuclear pores
Allow selective transport, open to the cytosol
What can move through nuclear pores freely?
Ions and small molecules
What is regulated through nuclear pores?
Proteins and nucleic acids
DNA Organization
DNA -> Nucleosomes -> Chromatin -> Chromosomes
Euchromatin
Loose DNA is accessible
Heterochromatin
Compact DNA is inaccessible
How was it discovered nucleic acids weren’t proteins?
Unaffected by pepsin, which breaks down proteins
What do nucleic acids contain?
Phosphorous, no sulfur
Avery-MacLeod McCarty Experiment
Evidence that DNA, not proteins, carries genetic info
What was the result of the Avery-MacLeod McCarty Experiment?
When injected with both heat-killed smooth strain (causes pneumonia) and rough strain (harmless) led to pneumonia
DNase treatment
DNA was damaged and the mouse lived
Protease treatment
Broken proteins and the mosue died
Hershey Chase Experiment
Bacteriophages consisting of DNA and proteins, infect bacteria with genetic material to replicate
In the Hershey Chase Experiment, what were proteins labeled with?
Sulfur
In the Hershey Chase Experiment, what was DNA labeled with?
Phosphorous
What was the result of the Hershey Chase Experiment?
After the infection, the bacteria showed only phosphorus (DNA) labeling
Nucleotide properties
Phosphate group, base & pento sugar
Nucleoside properties
Base, pento sugar
Purines
Adenine (a), Guanine (G0
Pyrimidines
Cytosine (C, DNA), Thymine (T, DNA & RNA), Uracil (U, RNA)
Ribose and Deoxyribose Pentose Sugar
Carbon 1 links the base, Carbon 2 identifies sugar, and Carbon 3&5 forms the phosphodiester bond (backbone)
What is the difference between Ribose and Deoxyribose Pentose Sugar?
Ribose: OH on Carbon 2
Deoxyribose: H on Carbon 2
Structure of phosphodiester bonds
OH on the 3’ carbon of the first nucleotide binds the phosphate group on the 5’ carbon of the second nucleotide
Nucleic acid polymer nomenclature
Name bases (A, T, G) starting at 5’ end
Chargaff’s Rule
A=T
G=C
Watson and Click
DNA was double helix and not triple helix
Bases faced inwards and outwards
DNA orientation
Antiparallel
How do base pairs interact?
Hydrogen bonds
How many hydrogen bonds are there between A-T?
Two H-bonds
How many hydrogen bonds are there between C-G?
Three H-Bonds
Base pair rationale
To form H bonds there must be an optimal distance
Why can’t 2 purine form?
They will not fit
Why can’t 2 pyrimidines form?
They will be too far apart
Hydrogen bonds can’t form between what bases?
GT and AC
DNA is only duplicated for _________
Cell division
Each cell only has _____ copy of DNA
One
The entire genetic code is copied into ___________
Two identical daughter cells
What is helicase?
Breaks H-bonds between base pairs
What is DNA primase?
Creates RNA primer
What is DNA polymerase?
Reads template sequence 3’-5’ and write 5’-3
What is DNA ligase?
Joins Okazaki fragments
What are Okazaki fragments?
A short sequence was found on the lagging strand
The leading strand is ______
Continuous
The lagging strand is ____
Made in pieces
DNA creates _______
Two identical DNA double helices, one original and one daughter strand
