DNA Replication: Unit 2
What are the steps of DNA replication?
1. Strands of DNA seperate 2. base pairing 3. Bonding Nucleotides 4. Result of Replication
Preventing the separating DNA strands from reforming their hydrogen bonds ...
Gives other enzymes the opportunity to attach to the single stranded DNA in order to carry out replication
What directional does DNA polymerase read the template strand?
In the 3'-5' direction
What directional does DNA polymerase produce a new DNA strand?
In the 5'-3' direction
Does gradual loss of these sequences harm the cell?
It does not harm the cell
What does helicase enzymes do as replication of a DNA molecule proceeds?
It moves down the length of the DNA molecule opening more single stranded DNA that can be used as templates for replication
what happens to the replication for during replication?
It moves down the length of the DNA molecule unwinding and replicating more DNA and expanding the size of the replication bubble
One template is called the...
Leading strand
On what strand does DNA polymerase can continue to make a new DNA strand until the end of a chromosome is reached
Leading strands
During DNA replication the two strands of a DNA molecule separate and each is used as a _____________ to make a new complementary strand
Template
What is cell division used for?
To create the cells and tissues that make up an organism during embryonic development and replaces cells that have been worn out or damaged in adults
What happens after the tension in the DNA is released?
topoisomerase reforms the covalent bonds in the sugar phosphate backbone.
Each two daughter cells that can divide and produce how many more daughter?
two more daughter cells
During cell division...
a cell splits to form two daughter cells
What cells are generated from a single starting cell?
a fertilized egg
What are telomeres?
Specialized DNA sequences at the ends of the chromosome
Enzyme Topoisomerase ________________the sugar phosphate backbone of one strand of DNA?
temporarily cuts
Why is copying the ends of these chromosome is a challenge?
Because of the way DNA is replicated
Telomerase
An enzyme that can add more copies of the repeated sequence found in the telomeres on to the ends of the chromosome
In what locations does DNA replication begin?
At multiple different locations along a DNA molecule
Where does replication of DNA molecules begin at?
At special regions called origins of replication
Why is DNA able to quickly replicate and accurately copy DNA molecules?
Because of the structure of these DNA molecules
How does two new identical daughter cells obtain a complete set of DNA that identical to the original DNA?
By copying thier DNA using the proces of DNA replication
How do cells with linear chromosomes deal with chromosome losing valuable information and becoming unstable?
By maintaining telomers
What do some cells replace and repair cells in damaged or worn out tissue?
Continuously divide
What two things are DNA polymerase able to do?
Continuously replicate the newly opened template DNA and can produce a long strands of complementary DNA
Guanine (G) nucleotides on one DNA strand always form base pairs with...
Cytosine (C) nucleotides on the other strand
How does DNA ligase form a single continuous strand?
DNA ligase can form covalent bonds between the sugar phosphate backbones of the new DNA segments joining them together
Why are primers needed for DNA replication?
DNA polymerase can only add nucleotides to the 3'end of an existing nucleotide chain
Why cant DNA polymerase continue to make a new DNA strand until the end of a chromosome is reached on the lagging strand?
DNA polymerase needs an RNA primer to provide a starting point for replication
True or False: Neither of the DNA strands separate by helicase at a replication fork are used as templates to make new complementary strands
False: Both of the DNA strands seperate
What does cutting one strand of DNA allow?
For DNA molecule to untwist
DNA polymerase
Enzymes read the DNA sequence of a template strand and insert new, complementary DNA nucleotide across from it to form a new DNA chain
Helicase
Enzymes separate the two strands of a DNA molecule so that each strand can serve as a template for production of new complementary DNA strands
Most eukaryotes organize their DNA into ______________ chromosomes?
Linear
RNA Primase
Make "Primers" on the template DNA strands
Since DNA replication begins at multiple locations...
New DNA strands are produced as several separate pieces
DNA polymerase moves in the ______________ direction as the helicase enzyme and away from the replication fork
Opposite
In Helicase strand separation begins at specialized regions called...
Origins of replication
How many cells is the human body is composed of?
Over 1,000,000,000,000 cells
Single strand binding proteins (SSBPs)
Prevent the separated DNA strand from reforming their hydrogen bonds
What creates several smaller pieces of a new DNA
Production of a complementary DNA strand is restarted again and again as helicase opens new regions of template DNA
______________ provides these ends and are later removed and replaced with DNA nucleotides
RNA primers
What are telomeres composed of?
Repetitive sequences of nucleotides that do not code for information needed by cells
What does separating double stranded DNA into two individual strands create?
Replication form
The DNA polymerase moves in the _______________ direction as the helicase enzyme opening up new template DNA at the replication fork
Same
What creates a replication bubble?
Separating the strands in a DNA molecule for replication with a Y-shaped replication fork at each end
What are Okazaki fragments?
Several smaller pieces of new DNA
Primers
Short stretches of complementary RNA
Why does production of a complementary DNA strand must be restarted again and again as helicase opens new regions of template DNA?
Since DNA polymerase moves in the opposite direction as the helicase enzyme and away from the replication fork
What happens when the chromosome continues to becomes shorter every time the DNA is copied?
The chromosome may begin to lose valuable information and can become unstable
What causes tightly putting stress on the DNA molecule?
The double stranded DNA in front of helicase to twist even more
What is the other template called?
The lagging strand
What happens after the bubbles merge until the whole DNA molecule is eventually replicated?
The result of this process is the production of two double stranded DNA molecules with the same DNA sequences
What makes two double stranded DNA molecules each with the exact same sequence of nucleotides?
The separation of two strands of a DNA molecule that is used as a template to make a new complementary strand
What happens to the replication bubble during replication?
The size expands
Topoisomerase
The two separate strands of a DNA molecule spiral tightly around each other in a helical pattern
Why does replication take place somewhat differently for each of the template strands?
The two strands of a DNA molecule have opposite directionality and that DNA polymerase produces the new DNA strand in the 5-3' direction and must read the template strand in the 3'-5' direction
Why causes the chromosome to become shorter every time the DNA is copied?
The unreplicated end of the lagging stand is lost
What happens when the RNA primer is removed?
There is no 3' end onto which DNA polymerase can add new nucleotides and the very end of the lagging strand remains unreplicated
Do telomeres contain critical information?
They do not
What happens to bubbles formed at different locations along DNA during replication?
They eventually merge until the whole DNA molecule is eventually replicated
Adenine (A) nucleotides pair with ...
Thymine (T)
What directionality does DNA polymerase add new nucleotides to the 3' end of a new DNA strand?
To the 3' end of a new DNA strand
What reduces the twisting of the double stranded DNA in front of helicase?
Topoisomerase
True or False: DNA polymerase can only add nucleotides onto 3' of an existing DNA strand and use the DNA and use the short RNA primer created by primase as a starting point
True
True or False: In DNA replication the nucleotides in one strand are complementary to nucleotides in the others?
True
True or False: The two new daughter cells that are produced must have a complete set of DNA that is identical to the DNA in the original starting cell
True
How many daughter cells are produced when a cell divides?
Two new daughter cells
How many strands is DNA molecule composed of?
Two strands of DNA
What causes The double stranded DNA in front of helicase to twist even more?
When helicase enzymes separate the DNA strands at the replication fork?
How are stem cells and gametes able to avoid having their chromosomes get shorter?
With the help from the enzyme telomerase
Cells are generated from...
a single starting cell
How long does cell division last?
from fertilization through adulthood until an organism dies
DNA molecule untwisting ________________ the surface tension on the molecule?
reduces