Molecular Bio Flashcards
What is molecular biology?
**concerns the molecular basis of biological activity that occurs between biomolecules in the various systems of a cell, including the interactions between DNA, RNA, proteins and their biosynthesis, as well as the regulation of these interactions
study of the molecular foundation of the processes of transcription, translation, replication, cell function
The ‘central dogma’ of molecular biology, where genetic material is transcribed into RNA and then translated into protein, despite being an oversimplified picture of molecular biology, still provides a good starting point for understanding this field. This picture, however, is undergoing revision in light of emerging novel roles for RNA”**
- The central dogma of molecular biology explains the flow of genetic information within a biological system. It was first stated by Francis Crick in 1956, and re-stated in a Nature paper published in 1970
- “The central dogma of molecular biology deals with the detailed residue-by- residue transfer of sequential information. It states that such information cannot be transferred back from protein to nucleic acid.”- Francis Crick-
- Crick’s use of the word ‘dogma’ was unconventional, and has been controversial.
This genetic material must be able to do what?
- have info. necessary to construct an entire organism
- pass from parent to offspring; cell to cell, cell division
- An accurate copy
- Account for the known variation within and between species (be able to help in differentiating itself from another species)
a. History: from 1920s to 1940s scientists thought which portion of chromosomes to be the genetic material?
protein
Frederick Griffith: what’d he do?
(ff = cc in streptococcus; c -> capsule)
- “bacterial transformation”
- he worked with streptococcus pneumonia
- rough strains (R) without capsules are non-fatal as the R strain bacteria (s. pneumonia) doesn’t have a capsule to protect itself from immune cells
- Smooth strains S have capsules thus are fatal however heat-killed type S not fatal
- BUT THEN AGAIN when R mixed with heat-killed S found that living type R cells have been transformed into virulent type S cells as this trait gave the R the capsule and was passed down to their offspring
he didn’t know the “transforming principle”’s biochemical basis (he still thought this transforming thing was protein)
Building off of Griffith’s work on transforming bacteria, what did Avery, MacLeod and McCarty (north Americans) find and how?
- Only purified DNA from type S strain which could transfer to type R
- Purified DNA might still contain traces of contamination that may be the transforming principle
- added (cell lysates from the pathogenic type) DNAase to digest DNA, RNase and proteases
- only w/ DNase no transformation as it had removed DNA thus it was concluded that DNA was the GENETIC MATERIAL (transforming principle)
Solving DNA structure
what did Watson and Crick propose the structure of and which method/structures did they use?
Did they receive any prize for it?
who else worked with them and what’d they do?
they proposed the structure of the DNA double helix and they used Linus Pauling’s method of working out the protein’s structure using ball and stick models; found ball and stick model consistent with data
They received the noble prize for this discovery
Rosalind Franklin: helped visualize the structure using x-ray diffraction that also provided imp. info.
Franklin died prematurely and nobel prize is NOT awarded posthumously.
Erwin Chargaff (Ukrainian guy): analyzed base composition of DNA that also provided imp. info.
Structure of nucleic acid
nucleic acid is a what?
what does it consist of “A”? what does this “A” consist of?
nucleic acid is a polymer
it consists of a chain of nucleotides which contains 3 basic building blocks:
phosphate
sugar
nitrogenous base
DNA’s structure has/is?
double-stranded
helical
sugar phosphate backbone
“bases on the inside (nitrogenous bases)!” which are stabilized by H bonding
specific pairing of nitrogenous bases (AT/GC)
(H bone can be easily broken)
3 components of DNA and RNA
phosphate group
nitrogenous base
- purines (“double/two ring” - IMP!): A & G
- pyrimidines: C & T
Deoxyribose sugar (pentose sugar)
RNA: same except “U instead of T” (IMP!) and ribose sugar (also pentose) instead of deoxyribose sugar
Conventional numbering system of DNA? e.g. phosphate on which # of C and nitrogenous on which ?
phosphate on the 5th carbon
nitrogenous base on 1st C (see screenshot)
Strands
how are they bonded?
which bond links sugars?
which 2 components of DNA form backbone?
bases project from backbone?
directionality from 5 to 3
or 3 to 5?
nucleotides covalently bonded so pretty strong
phosphodiester bond (between 3rd (top) and 5th carbon of sugars)
phosphate and sugar
yes
5 prime to 3 prime (TACG)
“Chargaff’s Rule”
it is also known as? (hint: nitrogenous base)
how many base pairs turn?
the DNA strands are what and what?
AT/GC
10 base pairs
complimentary (nitrogenous base); antiparallel
(lesser AMINO ACIDS than codons)
What are the buildings of DNA and RNA?
DNA is associated with an array of diff. what?
what is the complete complement of an organism’s genetic material?
nucleotides
proteins (histones etc.)
genome
n which groove does protein bind to to regulate transcription or replication?
major groove
DNA replication: what happens? short summary
what is the site of start point for replication known as?
is it uni or bidirectional? replication proceeds in same or opposite directions?
how many origin does bacteria and eukaryotes have?
The parental strands separate and serve as template strands
new nucleotides must obey the AT/GC rule
End result 2 new double helices with same base sequence as original
- origin of replication (note: not promoter as its not transcription)
- bidirectional; opposite
- bacteria has one and eukaryote has multiple
