Dma Flashcards
What is the Central Dogma of Life?
The Central Dogma holds that genetic information is expressed in a specific order, from DNA to protein synthesis.
What are the main processes involved in the Central Dogma?
- DNA replication
- Transcription (RNA synthesis)
- Translation (protein synthesis)
What is DNA replication?
DNA replication is the process of making copies of DNA.
What serves as a template during DNA replication?
A single strand of DNA serves as a template for a new strand.
What directs the replication of DNA?
The rules of base pairing direct replication.
When does DNA replication occur in the cell cycle?
DNA is replicated during the S (synthesis) stage of the cell cycle.
What does each complete cell receive after DNA replication?
Each complete cell gets an identical DNA.
How many models of DNA replication are there?
There are three (3) models of replication.
What are the three models of DNA replication?
- Semiconservative
- Conservative
- Dispersive
These models describe how DNA strands are duplicated during cell division.
Describe the semiconservative model of DNA replication.
Each daughter strand has 1 parental and 1 new strand
This model shows that during replication, one original strand is retained in each new double helix.
What characterizes the conservative model of DNA replication?
Both parental strands stay together
In this model, the entire double helix is preserved, and a completely new double helix is formed.
Explain the dispersive model of DNA replication.
DNA is fragmented; both new and old DNA coexist in the same strand
This model suggests that the parental DNA is broken into pieces and intermixed with newly synthesized DNA.
What does ‘semiconservative replication’ mean?
In each new double helix of DNA, one strand is from the parent
This term emphasizes that half of the parental DNA is conserved in each daughter molecule.
What experimental evidence supported the semiconservative model of DNA replication?
Meselson and Stahl experiments
Their experiments used isotopes of nitrogen to trace the distribution of parental and new DNA strands.
True or False: In the conservative model, new DNA strands are formed from fragments of parental DNA.
False
The conservative model maintains the parental strands intact and creates entirely new strands.
Fill in the blank: In the _______ model of DNA replication, DNA is fragmented and both new and old DNA coexist in the same strand.
Dispersive
This model illustrates a mixed composition of DNA strands after replication.
What happens during the first replication in semiconservative replication?
One parental and one new strand are formed
This results in two double helices, each with one original strand.
What occurs during the second replication in semiconservative replication?
Continued formation of double helices with parental and new strands
This process leads to an exponential increase in the number of DNA strands.
What are the three models of DNA replication?
Conservative model, Semiconservative model, Dispersive model
These models were proposed to explain how DNA replicates.
What did the Meselson and Stahl experiments aim to demonstrate?
The method of DNA replication
The experiments specifically tested the predictions of the three models of replication.
What is the outcome of the Meselson and Stahl experiment after three generations?
Mix of heavy and light DNA strands
This demonstrates the semiconservative model, where each new DNA molecule contains one original and one new strand.
What is the role of helicase in DNA replication?
Unwinds parental double helix at replication forks
Helicase is essential for separating the two strands of DNA to allow replication.
What does the single-strand binding protein do during DNA replication?
Binds to and stabilizes single-stranded DNA until it is used as a template
This prevents the single strands from re-annealing or forming secondary structures.
What is the function of topoisomerase/DNA gyrase in DNA replication?
Relieves overwinding strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands
This helps to prevent supercoiling of the DNA ahead of the replication fork.
What is the role of primase in DNA replication?
Synthesizes an RNA primer at 5’ end of leading strand and at 5’ end of each Okazaki fragment of lagging strand
RNA primers are necessary for DNA polymerases to begin synthesizing new DNA strands.
What is the function of DNA polymerase III?
Synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand
DNA polymerase III is the primary enzyme involved in DNA synthesis.
What does DNA polymerase I do during DNA replication?
Removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides added to 3’ end of adjacent fragment
This enzyme ensures that the RNA primers are replaced with DNA, completing the new DNA strand.
Fill in the blank: The Meselson and Stahl experiment used _______ nitrogen to differentiate between DNA strands.
light nitrogen
Light nitrogen was used alongside heavy nitrogen to track the replication process.
True or False: The conservative model of DNA replication suggests that the original DNA strand remains intact.
True
In the conservative model, the entire original DNA molecule is preserved while a new molecule is synthesized.
