Chapter 6 -> DNA Replication, Repair, and Recombination Flashcards
What type of cells divide via Mitosis and what is the literal meaning of the word?
Somatic Cells AKA Body Cells
What type of cells divide via Meiosis
Gametes
Before the division of a cell by either mitosis or meiosis, what must occur within the DNA?
It must replicate itself
In the beginning of DNA replication, the two complementary strands of the DNA double helix are pulled apart into _ single strands, which serve as ________ for copying two new strands
What is the resulting DNA’s name since it is half old strand and half new strand?
2, templates
SEMI-CONSERVATIVE
Replication is initiated by DNA _____ enzyme that separates the two strands of nucleotides like “unzipping” them, breaking down the hydrogen bonds between the complementary bases, creating what is known as a _______
Helicase
Replication Fork
As the Helicase enzyme unzips the DNA double helix, _______ _______ binding proteins attach to each strand and prevent the double helix from reforming
Single Strand
The separation of the DNA double helix occurs in areas known as the __________
Origin of Replication
Why is the Origin of Replication typically AT rich instead of GC?
AT bases only have 2 hydrogen bonds holding them together, making it easier to unzip rather than 3
Bacterial Chromosomes have ____ origin of replication while eukaryotic chromosomes have ______ origins of replication
1, Multiple
DNA is ______ because there are two ___________ forks that begin to move in opposite directions
Bidirectional, replication
After a replication fork has formed in DNA, short sequences of RNA, called ___________, are synthesized by the enzyme ________
This short RNA primer allows DNA polymerase 3 to function
RNA Primers, Primase
DNA polymerase 3 binds to each nucleotide of DNA moving along the strand using it as a template to copy a new strand of DNA
What direction does DNA polymerase 3 work and what is this strand called?
What happens to the strand that is not 5’ to 3’ since DNA polymerase only works in that direction?
5 Prime to 3 Prime direction, Leading Strand
The other strand is known as the lagging strand because replication is not continuous and results in the formation of Okazaki Fragments
What are the fragments of DNA that DNA polymerase creates when working on the lagging strand?
Okazaki Fragments
What enzyme removes the RNA primers when they are done being used?
DNA polymerase 1
What fills in the gaps left by RNA Primer removal?
DNA polymerase 1
What enzyme forms the covalent bonds between DNA fragments to ensure that there are no gaps?
DNA LIgase
While DNA replication is occurring, torsional forces build up. What two things provide relief?
Topoisomerase & Supercoiling
What strand loses a little bit of DNA due to the telomere caps?
The lagging strand
DNA Replication Summary:
1) DNA Helicase ______ the double strand starting at an AT rich origin of replication
2) Both ________ and ________ relieve torsional stresses
3) Single strand binding proteins stabilize the unzipped DNA
4) ________ ________ builds a short RNA primer to allow DNA polymerase 3 to function
5) DNA polymerase 3 enters and begins adding complementary ________ to the 3’ end
6) DNA polymerase can only function in the __ to _____ direction- the leading strand involves continuous synthesis
7) * The antiparallel lagging strand must be synthesized in the direction leading ______ from the replication fork
8) The lagging strand also requires short (____ nucleotide) primers for DNA polymerase to function in this direction
9) In this manner, Okazaki fragments are formed- lagging strand discontinues synthesis
10) When DNA polymerase 3 reaches the previously added RNA primer, it is replaced by __________
11) DNA polymerase 1 then removes the RNA primer nucleotides and replaces them with _____ nucleotides
12) DNA ligase then enters and connect the backbones via ________ bonds
13) DNA polymerase 3 then jumps ahead to the newly added RNA primer and begins to synthesize the next ______ fragments
14) In realtime, both strands are synthesized by a dimer of ____ _______ _ made possible by a loop in the lagging strand
1) Unzips
2) Supercoiling and Topoisomerase
4) RNA Primase
5) Nucleotides
6) 5’ to 3’
7) Away
8) 10
10) DNA polymerase 1
11) DNA
12) Covalent (Phosphodiester)
13) Okazaki
14) DNA polymerase 3
What 3 things can cause Mutations?
1- Error in DNA replication
2- Change in the DNA
3- X-rays, UV light, mutagens
Most common mutations are _________
Single nucleotide polymorphisms
DNA is read in codons (group of 3 Nucleotides) so one changed nucleotide fucks it up
What is a silent mutation?
The codon that was changed still codes for the same amino acid so there is “no” difference
What is a missense mutation?
Mutates to form a different amino acid that changes the protein’s structure and function
What is a nonsense mutation?
The mutation changes an amino acid into a stop codon which ultimately forms a short proteins
What is a frameshift?
The frame AKA the 3 nucleotides that make up the codon will be off every frame after say an insertion or deletion takes place
How are mutations inherited?
How are mutations acquired?
They can be passed on through gametes BUT ONLY GAMETES NOT SOMATIC
They can be acquired by occurring in the genome of somatic cells BUT WILL NOT BE PASSED TO OFFSPRING
What is Sickle Cell Anemia-> Inherited or Acquired
Inherited-> Change from an A to a T in the B chain causes a change in amino acid- glutamic acid to a valine
Individuals must inherit 2 copies of mutant gene
What is Sickle Cell Anemia-> Inherited or Acquired
Inherited-> Change from an A to a T in the B chain causes a change in amino acid- glutamic acid to a valine
Individuals must inherit 2 copies of mutant generate
What is so special about DNA polymerase?
It has a proof reading ability so that before it adds a new nucleotide onto a growing chain it checks to see if the previous nucleotide was correct
If the is a mismatch in DNA, what happens?
DNA mismatch repair system removes replication errors and re-synthesizes it
What is Depurination?
Loss of A and G basses
What is Deamination?
Loss of amino groups from C to form a U
What occurs when an individual has thymine dimers and what is the disease called?
Occurs when two thymine bases form a covalent bond because of the UV light that was present. It is called Xeroderma Pigmentosum, causing severe skin lesions to skin
One Cell produces two daughter cells that each contain an ______ copy of DNA from the parent cell
Identical
