these are the building blocks of DNA, where two phosphate groups are released and 3rd is bound to 3 end
what does DNA replication begin with?
The binding of a large protein complex to a specific site on the DNA molecule
What does the large protein complex contain? What does it do?
It contains DNA polymerase which catalyzes addition of nucleotides.
Where does the large protein complex bind to
The ori origin of replication
Where does the DNA unwind
How would replication be sped up
If a chromosome was linear and had multiple origins of replication
What do you first need to begin DNA replication
A primer- a starter strand; it is complementary to the dna Template. You then need a primase (enzyme) to synthesize dna one nucleotide at a time.
Where does DNA polymerase add nucleotides
To the 3 end
DNA polymerases are larger than
Their substrates, dNTPs, and the template DNA
In the hand shape enzyme, what does the palm and fingers do
Palm bring the active site and substrate together, fingers recognize nucleotide bases
What direction does DNA replicate
How is the leading strand oriented to grow
It grows its 3 end as the fork opens
How is the lagging strand oriented
So that its 3 end is exposed and gets farther from the fork.
What are okazaki fragments
Synthesized lagging strands that occur in small discontinuous stretches
What does each okazaki fragment require?
It requires its own primer, synthesized by primase
How does fragmentation happen in Okazaki fragments
DNA polymerase adds nucleotides to 3 until it reaches the primer of the previous fragment, a different DNA polymer replaces primer with DNA. The final phosphodiester linkage is catalyzed by DNA LIGASE
DNA polymerase is very fast and it is processive. What does this mean?
It means it catalyzes many sequential polymerization reactions each time it binds to DNA.
Okazaki fragment are added to RNA primers for what purpose
To replicate lagging strand
When does fragmentation end in okazaki fragments
When the last primer is removed because there is no more 3 to extend.
What happens to the ends of okazaki fragments
The ends are cut after replication and chromosome is slightly shortened after each division
What are telomeres
Repetitive sequences at the ends of eukaryotic chromosomes.
What do telomeres do
They prevent the chromosome ends from being joined by DNA repair system
What is telomerase and what does it do
It contains RNA sequence; acts as template for telomeric DNA sequences. Lost over time in most cells but not in cells that continuously divide, like bone marrow and gametes
How can errors in DNA replication be fixed
Proofreading, mismatch repair
How does proofreading work in repair mechanisms
If bases are paired incorrectly, the nucleotide is removed
How does mismatch repair work in repair mechanisms
Other proteins scan for mismatched bases missed during the proofreading. They them replace them with the correct ones
That are the 5 things that PCR technique requires
Double stranded DNA sample, two short primers complementary to ends of sequences to be amplified. Four dNTPs, a DNA polymerase that works at high temps, Salts and buffer
Changes in the nucleotide sequence of DNA that are passed on from one cell to another
Two ways errors that are not corrected can be passed on to daughter cells
Somatic mutations & germ line mutations
What are somatic mutations
They occur in somatic cells; passed on by mitosis bu not to sexually produced offspring
What are germ line mutations
Give rise to gametes; passes mutation at fertilization.
Which type of mutations do not affect protein function
What happens in a loss of function mutation?
Proteins are affected and may lead to structural proteins or enzymes that dont work anymore; they are almost always recessive
What happens in a gain of function mutation
It leads to a protein with an altered function
What is a conditional mutation
It means the phenotype will work under restrictive conditions, maybe temperature, but may not be detectable under permissive conditions
What are the two categories of mutations
Point and chromosomal
What is a point mutation
It results from the gain, loss or substitution of a single nucleotide
What is a chromosomal mutation
It is more extensive than a point mutation; it may change the position of cause a DNA segment to double or disappear