Central Dogma: Molecular Basis of Heredity -- DNA, RNA, & Proteins Flashcards
What are the 3 basic component of a nucleotide?
- Nitrogenous bases
- Pentose sugar
- Phosphate group
Under the nitrogenous bases, what are the compontents?
Nitrogenous bases
- Purine bases: Adenine & Guanine
- Pyrimidine bases: Thymine & Cystosine (in RNA: Uracil instead of Thymine)
Under the pentose sugar, what are the compontents?
DNA: Deoxyribose
RNA: Ribose
Pentose sugar + Nitrogen base
Nucleoside
Phosphate group + Pentose sugar + Nitrogen base
Nucleotide
Who demonstrated how the 3 nucleotide components are physically assembled to form DNA?
Watson & Crick
It is a model of DNA where it is like a twisted ladder with chemical bonds as its rungs
Double Helix model
Discovered by Watson & Crick
Nucleotides are joined to form a __________
polynucleotide chain
- Covalent bond that links adjacent nucleotides
- 5’-phosphate group of the new nucleotide is linked to the free 3’-OH group of the existing nucleotide
Phosphodiester bond
Enumerate the nitrogenous base pairing
- Adenine and Thymine
- Guanine and Cytosine
- In RNA: Adenine and Uracil
How many hydrigen bonds are there for the following:
- A – T pair has ____ hydrogen bonds
- G – C pair has ____ hydrogen bonds
- A – T pair has two hydrogen bonds
- G – C pair has three hydrogen bonds
In a DNA duplex, the ____ end of one strand is opposite the ____ end of the other
Have opposite orientations = antiparallel
5’ end to 3’ end
These are important for the attachment of DNA Binding Proteins involved in replication and transcription
Major and minor grooves
It is important in duplicating the DNA so that there will be sister chromatids at anaphase stage and at the end of cytokinesis, each daughter cell would have the genetic material.
Replication
True or False
**DNA replication **is described as Semiconservative
False
What are the major steps in DNA Replication?
- Unwinding of the double stranded DNA
- DNA synthesis
- Rewinding of the double helix
It unwinds the two DNA
strands at the replication fork
Helicase
It stabilizes the DNA as it forms so it will not anneal to reform the double helix
Single-strand DNA binding proteins (SSB)
It releases the tension (positive supercoils) ahead of the replication fork caused by the unwinding of the DNA helix
DNA Gyrase
Replication
- Unwinding of parental strands through Helicase protein binding creating a ______
replication fork
Replication
What step of replication is this?
Stabilizing the ssDNA through the single-strand DNA binding proteins (SSB) at the replication fork
2nd step
Replication
What step of replication is this?
Primase binding at the replication fork to synthesize short RNA primer, needed at the start of DNA synthesis, since it provides the 3’-OH group, to which new nucleotides are added
3rd step
Replication
In the 4th step of replication, ________ binding at the DNA template which adds DNA nucleotide at the RNA primer
DNA polymerase
Replication
In the fifth step of replication, ________ in a 5’ to 3’ direction to both Parental DNA template
adding of nucleotides by DNA polymerase
Replication
In the sixth step of replication, the other strand produced short fragments aka ________, known as
Okazaki fragments (discontinuous synthesis)
In the seventh step of replication, ________ proofreads the newly synthesized DNA and replacing incorrect bases
DNA polymerase
In the eighth step of replication, ________ rewinds the DNA double helix and ________ seals the sugar phosphate
Annealing helicase; Ligase
What is the summary of the DNA Replication process?
- Helicase unwind the parental double helix
- **SSB **stabilies the ssDNA
- Primase binding at the replication fork to synthesize short RNA primer
- DNA polymerase binding at the DNA template ——> adds DNA nucleotide at the RNA primer
- The leading strand is synthesized continuously in the 5 ——> 3 direction by the DNA polymerase
- The lagging strand produced Okazaki fragments
- DNA polymerase proofreads and corrects the newly synthesized DNA
- Anneling healicase rewinds the DNA & Ligase seals the sugar phosphate
It is the process by which an RNA sequence is formed from a DNA template
Transcription
What are the major steps of Transcription?
- Initiation
- Elongation
- Termination
What are the two complementary DNA strands in transcription?
- Template strand
- Coding strand
Between the two complementary DNA strands in transcription, what has these characteristics:
- is used for RNA synthesis and is
- aka the antisense strand
Template Strand
Between the two complementary DNA strands in transcription, what has these characteristics:
- Has the same sequence as the RNA produced, with exception of U replacing T
- Non-template strand
- Aka: sense strand
Coding strand
Type of RNA produced by the transcription process
Messenger RNA (mRNA)
In the 1st step of transcription, one of the RNA polymerase enzymes (RNA polymerase II for mRNA) ________ to a promoter site on the DNA
binds
In the 2nd step of transcription, ________ pulls a portion of the DNA strands apart from each other, exposing unattached DNA bases
RNA Pol