1B Flashcards
Components of DNA
- Pentose sugar (RNA-ribose or DNA-deoxyribose)
- Nitrogenous base… Purine (adenine guanine) and Pyrimidine (cytosine, uracil,thymine)
- Phosphate
RNA vs DNA sugar
RNA-ribose is pentose with OH, OH
DNA-deoxyribose is pentose with OH, H
Where is the diff between DNA and RNA
2’carbon
Nitrogenous bases of DNA and RNA
Pyrimidine (1 ring-6): cytosine (NH2, N, O, NH) AND thymine (Ch3, O, NH, O, NH) AND uracil (O, NH, O, NH)
Purine (2 rings-5): adenine (NH2) AND guanine (O, NH, NH2, N)
Where do ribose/deoxyribose sugars bind on purines
N9
Where do ribose/deoxyribose sugar bind on Pyrimidine
N1
Nucleoside?
Sugar+base
Deoxyribonucleoside?
2-deoxyribose sugar+ purine/Pyrimidine base
Where does the nitrogenous base bind on the deoxyribonucleoside….
C1’ of deoxyribose/ribose
What is deoxyadenosine
2-d+ adenine
Deoxyguanosine
2D+ guanosine
Thymidine??
2D+ thymine
Ribonucleoside??
Ribose sugar+ purine/Pyrimidine base
Adenosine
Ribose+ adenine
Guanosine
Ribose+ guanine
Cytosine?
Ribose+ cytosine
Uridine
Ribose+ uracil
Nucleotides
Nucleoside+phosphate
Where is the phosphate group attached on nucleotides
C5’ of ribose/deoxyribose sugar
.dATP
Deoxyadenosine triphosphate (3x PO4, deoxyribose, adenine)
.dTTP
Deoxythymidine triphosphate (3x PO4, deoxyribose, thymine)
.dGTP
Deoxyguanosine triphosphate (deoxyribose,3xPO4, guanine)
.dCTP
Deoxycytidine triphosphate(deoxyribose, 3xPO4, cytosine)
What is DNA made of
Polymer of deoxyribonucleotides
How do nucleotide monomers polymerize (assemble)
Phosphodiester bonds (C-O-P-O-C)
What bonds make the pentose-phosphate backbone
Covalent bonds between phosphate and C3 and C5 of 2 pentose sugar
What is 5’ end of DNA
PO4 end
What is 3’ end of DNA?
Hydroxyl end
Is DNA polar or nonpolar
Polar (5’ PO4 and 3’ OH)
What is the charge on DNA
Neg. Cause neg. PO4
3D structure of DNA components
- Linear
- Pentose-phosphate backbone
- Nitrogenous bases in nucleotide held code
Erwin chargaff conclusions
- Chargaff’s rule: %A=%T, %C=%G
- %purines (A+G)=%pyrimidines (C+T)
- A,C,G,T are never equal amounts
What was chargaff testing
Quantities of 4 nitrogenous bases in organisms
Rosalind franklin conclusion
X-Ray diffraction
1. DNA is cylindrical
2. Bases were stacked (periodicity)
3. X-shape
Watson and Crick conclusion
- Phosphate pentose backbone spiral (double helix)
- Anti parallel 5->3, 3->5
- Purine pairs with Pyrimidine
- Backbone/exterior is hydrophilic…. Base/interior is hydrophobic
What type of bonding between purine and Pyrimidine nitrogenous base
Hydrogen bond
What does guanine pair with
Cytosine
What does adenine pair with
Thymine
How many hydrogen bonds between G and C
3
How may h-bonds between adenine and thymine
2
Nucleic acid hybridization
1.temperature driven
2. [] dependent
2 options
1. Denature (alkali and heat)-> reaneal (cool)… DNA and DNA
2. Denature and add RNA-> RNA hybridizes to complementary DNA strand… DNA-RNA hybrid
Where are DNA-RNA hybrids
DNA replication
Transcription
Reproducing RNA viruses
Watson and Cricks conclusion
- Complementary base pairing=> parental strand as template for DNA replication of new strands
- Parental strand unwind (break h-bond)
3.semi conservative replication… parental+new - Direction of replication is 5->3
DNA general organization
-DNA with proteins=> chromosomes
-Chromatin=> region of DNA with protein on chromosome
Prokaryote DNA
Circular chromosome (1) + many small independent circular DNA (plasmids in cytoplasm)
Eukaryotic chromosomes
Linear and enclosed in nucleus
Critical components of eukaryotic chromosomes
-DNA replication (chromosome duplication)-> chromosome transmitted to each daughter cell (mitosis/meiosis)
1. Origin of replication
2. Centromere
3. Telomeres
Origin of replication??
DNA sequence along chromosome which initiate DNA replication
Centromere?
DNA sequence need for correct segregation along kinetic horse where mitosis spindle attaches
Telomere use??
DNA sequence at end of chromosome… prevent degradation and allow proper replication of chromosomal ends
Are the majority of eukaryotic cells diploid or haploid
Diploid (2 copies of each chromosome->homologous chromosomes)
Which eukaryotic cells are haploid
(1 copy of chromosome+ diff copy of 1 chromosome)
Sexually-reproductive cells
Can eukaryotes be polyploid
Yes… ex: large protists have more than 2 chromosome sets
Why is DNA organized as chromosomes
- Compact=> fit in cell/nucleus
- Protect DNA from damage (shield)
- Chromosome easily separated and transmitted to each daughter cell during cell division
Histone?
Basic positively charged protein… DNA winds around this
Nucleoside
Histone octameter (many DNA wrapped around)
What forms chromatin fibre
H1 (histone( linker DNA) and nucleosome
What type of histone do prokaryotes have
Prokaryotes dont have histones
Is dna packing/compaction uniform??
NAHHHH
Euchromatin??
-Region with lower DNA compaction
-genes actively expressed
Heterochromatin
-high DNA compaction of chromosomal region
-gene expression silenced
Constitutive heterochromatin
DNA HIGHLY compacted
Aka centromere and subtelomeric region
Facultative heterochromatin
Switch to euchromatin depending on cell type and during development