Jan 15 And 17 Flashcards
(25 cards)
Nucleic acids were discovered in ? Consist of equal parts like:
1869, 1.Pentose Sugar (Ribose (C5H10O5) - used in ribonucleic acids (RNA) , Deoxyribose (C4H10O5), (C5H10O4) - used in deoxyribonucleic acids (DNA )
2.Nitrogeneous base - Purines (double ring) - guanine and adenine, Pyrimidines (single ring) - cytosine, uracil and thymine 3. Phosphate (PO4)
Pentose sugars of DNA and RNA
*check pics of Ribose and 2-Deoxyribose (DNA), compare them
The two sugars for RNA and DNA only differ in the type of chemical group attached to the 2’ carbon.
Nitrogenous bases of DNA and RNA
Purine ring(NH9) both are purines bcs of the double ring, adenine, guanine.
DNA= A, C, G, T
RNA= A,C, G, U
Nucleosides: molecules of a sugar and a base, what are deoxyribonucleosides ,
Deoxyribonucleosides: 2-deoxyribose sugar + purine/pyramidine base
The ribose/ deoxyribose sugars bind to the N9 of purines and N 1 of pyramines to make deoxyribonucleosides
- Base binds to C1’ of deoxyribose/ribose
In nucleosides, Deoxyadenosine and deoxyguanosine have in common _____, Deoxythymidine and deoxycytudine have in common ____
N9 C1 (1). N1 C1 (2).
To turn nucleosides into nucleotides we need to ….
The phosphate group needs to be added.
Deoxyadenosine triphospgate (dATP), the tiny d at the front tells us that its the deoxynucleotide
Chain dATP
Adenine -> Adenosine -> adenosine menophosphate -> adenosine diphosphate -> adenosine triphosphate
DNA: a polymer of deoxyribonucleosides, What charge in DNA molecule?
- Nucleotide monomers polymerize via phosphodiester bonds ( C-O-P-O-C)
-Covalent bonds form between phosphate and the C-3’ and C-5’ of the 2 Pentose sugars (Pentose - phosphate backbone)
So phosphodiaster will have Oxygen double bond at P, Ester will have double bonded O to Carbon
-Polynucleotide has polarity with a C-5’PO4 end and a C-3’ OH end
-Type of nucleic acid depends on sugar (DNA = deoxyribose and RNA = ribose in pentose-phosphate backbone)
We gon give DNA negative( - ) charge overall
To determine the 3D structure of DNA
Based on the 3 chemical components of DNA, scientists knew that DNA:
- was relatively linear
-Had a pentose phosphate backbone
-The nitrogenous bases in the nucleotide “held the code” we know that because if we look at the pentose phosphate backbone its just the nitrogenous bases that held the code, we know that because its the same structure taking the look, there’s no variation
Erwin Chargaff analyzed overall quantities of the 4 nitrogenous bases in various organisms, what’s chargaff’s rule?
Charhgaff’s Rule: %A = ^%T: %C = %G
- Other conclusions:
1. %Purines (A+ G) = %Pyramidine (C+T)
2. C+G doesn’t equal A+T
3. A, C, G and T aren’t present in equal amounts
Rosalind Franklin discovered
-DNA molecules were cylindrical and about 2 nm in diameter.
-0.34 nm periodicity suggested that bases were stacked like pennies on top of one another
-X shape pattern indicates helical structure
-Franklin did not propose a definitive model
Then passed to Watson and crick
Piecing together the clues (Watson and Crick)
- Two strands of the phosphate - pentose backbone spiral as a double helix about a common axis
- The two strands run anti parallel ( one strand is In the 5’-3’ direction while the other strand is 3’-5’)
- A purine on one strand is always base- paired with a pyrimidine (fits Chargaff’s rule and the 2 nm diameter of the double helix)
- They realized that backbone (exterior ) is going to be hydrophilic and the bases (interior ) are hydrophobic
DNA double helix, distance between each pair of bases = ——nm
Each full twist of the double helix = ____ nm
0.34nm, 3.4 nm
- DNA base pairing is __________ and therefore base pair sequence on one strand can be used to specify the _______ of the other strand
- Base pairs are _______ _____ lying __________ to the axis and contribute to ________ of double helix
-_______ _______between bases keeps two strands intact , how many H-H bonds can purines and perimedes form?
-Complimentary, sequence
-Stacked flat, perpendicular , stability
-Hyrogen Bonding , forms 3 Hydrogen bonds between purines and only 2 Hydrogen bonds between the perimedes .
*Make sure bonds aren’t that strong so we are Able to separate those strands
Nucleic Acid Hybridization
Annealing of single strands of DNA or RNA by forming H-bonds
-Hyghly specifies (Two strands must be complimentary in sequence ), temperature-driven and concentration-depended
-DNA-RNA hybrids found in DNA replication, transcription and reproduction of some RNA viruses
1.Denaturing conditions -> ______, _________
2.Reannealing > ____ ______
3.Denatures and add ____
4.RNA hybridizes to -> complimentary ___ strand
- Heat, alkali 2. Cool slowly, 3.RNA 4. DNA
Watson and Crick’s model of DNA replication
Complementary base pairing allows
- ….
• _______ _______ can unwind by
breaking the ________ ______
between bases
• Semiconservative replication - where the double helix will contain a
________ ______ and a newly
_________ strand
Complementary base pairing allows
parental strands to act as templates
for DNA replication of new strands
• Parental strands can unwind by
breaking the hydrogen bonds
between bases
• Semiconservative replication - where
the double helix will contain a
parental strand and a newly
synthesized strand
•Human DNA has 3.2 billion ____ ____ (3200 Mb or 3.2 Gb)
• __ ______ packed in a cell 250 000 times smaller
•Eukaryotes have _____,_____ ___ molecules enclosed in a ______
•To keep the DNA organized, and help regulate ____ ________, it is condensed into ________
•The DNA ______ _____ is first wrapped twice(ish) around histone proteins to form a ________
•Each DNA molecule is a repeating series of nucleosomes, called ,___ ________ ______
that looks like _____ __ __ _______ under an electron microscope
•Additional histones cause the chromatin to coil further into _____ ________ fibres
(solenoids)
•Chromatin is the _______ state of our DNA molecules
• It unwinds during DNA ______, _________ and _______
• It condenses further - into ___________ during ________/________
•Human DNA has 3.2 billion base pairs (3200 Mb or 3.2 Gb)
• 2 meters packed in a cell 250 000 times smaller
•Eukaryotes have multiple, linear DNA molecules enclosed in a nucleus
•To keep the DNA organized, and help regulate gene expression, it is condensed into chromatin
•The DNA double helix is first wrapped twice(ish) around histone proteins to form a nucleosome
•Each DNA molecule is a repeating series of nucleosomes, called , 10nm chromatin fibres that looks like “beads on a string” under an electron microscope
•Additional histones cause the chromatin to coil further into 30nm chromatin fibres (solenoids)
•Chromatin is the “normal” state of our DNA molecules
• It unwinds during DNA replication, transcription, and translation
• It condenses further - into - chromosomes during mitosis/meiosis
•Histones are____ , ______-_______ proteins
•The ________ is a histone octamer ______________ with approximately
___ bp of DNA wrapped around it (1.65 X around outside of octamer)
•Histone H1 binds _____ DNA and to _________ to form the __ nm chromatin fibre
•Histones are basic, positively-charged proteins
•The nucleosome is a histone octamer [2(H2A, H2B, H3 and H4)] with approximately
147 bp of DNA wrapped around it (1.65 X around outside of octamer)
•Histone H1 binds linker DNA and to nucleosomes to form the 30 nm chromatin fibre
DNA ______/_________ along the chromosome is not ______
• Euchromatin regions have _____ DNA _______ and genes are actively _______
• _____________ are chromosomal regions of high DNA compaction where gene
expression is silenced
• Constitutive heterochromatin: DNA always highly ________ (centromeres and sub-telomeric regions)
• _______ _________: Can switch to __________ depending on cell type and during development
DNA packing/compaction along the chromosome is not uniform
• Euchromatin regions have lower DNA compaction and genes are actively expressed
• Heterochromatin are chromosomal regions of high DNA compaction where gene
expression is silenced
• Constitutive heterochromatin: DNA always highly compacted (centromeres and sub-telomeric regions)
• Facultative Heterochromatin : Can switch to euchromatin depending on cell type and during development
Chromosomes ______ ____so that it can fit into the ____/_______
_______ _______ protects DNA from damage (______ DNA is very ________)
Chromosomes can be easily ________ and ________ to each daughter cell
during _____ ________
Chromosomes compact DNA so that it can fit into the cell/nucleus
Chromosomal structure protects DNA from damage (naked DNA is very
unstable)
Chromosomes can be easily separated and transmitted to each daughter cell
during cell division
- Chromosomes need to be ______ __________
(DNA replication) and properly transmitted to _____ ______ _____ during mitosis/meiosis
1. _______ __ _________: multiple
DNA sequences along chromosome which
initiate DNA replication
2. Centromere: DNA sequences required for correct ________ of chromosomes by
directing formation of the ________ in
which the _______ ________ attaches
3. Telomeres : DNA ________ located at
the ____ of the chromosome that prevent
_________ and allow proper _________ of the chromosomal ends
•Chromosomes need to be fully duplicated
(DNA replication) and properly transmitted to
each daughter cell during mitosis/meiosis
1. Origins of replication : multiple
DNA sequences along chromosome which
initiate DNA replication
2. Centromere: DNA sequences required for correct segregation of chromosomes by
directing formation of the kinetochore in
which the mitotic spindle attaches
3. Telomeres : DNA sequences located at
the ends of the chromosome that prevent
degradation and allow proper replication of
the chromosomal ends
•Majority of eukaryotic cells are _______
(two copies of each _________ chromosome)
•Only ________-_________ ____ (e.g. sperm and eggs) have a _______
genome
•Some eukaryotes are _______ (more than a pair of each chromosome) such as
______ ______(Tetrahymena : 10-10,000 copies) and _______ _____
•Majority of eukaryotic cells are diploid
(two copies of each homologous chromosome)
•Only sexually-reproductive cells (e.g. sperm and eggs) have a haploid
genome
•Some eukaryotes are polyploid (more than a pair of each chromosome) such as
large protists (Tetrahymena : 10-10,000 copies) and flowering plants
-Prokaryotes typically have a _______ _______ ___ _________ found in the _______ (no nucleus)
•Prokaryotic DNA does not need the same level of _______ as eukaryotic DNA
- They use _______-______ proteins (HLPs), also called ______-_______ ______ (NAPs)
•Prokaryotes also have other ______ ____________ ______ DNA molecules called _________
- Each cell can have multiple _______ ______ , as well as multiple copies of each ________
•Plasmids only carry a ___ ______- none ________ for life
• They carry ________ _____ that give them an advantage in some environments
-________ ______ , ________, ____metabolism
•Prokaryotes typically have a singular, circular DNA molecule found in the cytosol (no nucleus)
•Prokaryotic DNA does not need the same level of compaction as eukaryotic DNA
• They use histone-like proteins (HLPs), also called nuleoid-associated proteins (NAPs)
•Prokaryotes also have other small independent circular DNA molecules called plasmids
• Each cell can have multiple different plasmids, as well as multiple copies of each plasmid
•Plasmids only carry a few genes - none essential for life
• They carry “Bonus genes ”that give them an advantage in some environments
-antibiotic resistance, virulence, rare metabolism
