Chapter 16 Flashcards
In Fredrick griffiths experiment why did the mice injected with both heat killed s cells and living r cells die, when neither one alone was fatal?
The r bacteria was transformed into an s bacteria by an unknown heritable substance
A change in genotype and phenotype due to the assimilation of external dna by a cell
Transformation
Viruses that infect bacteria
Bacteriophages
Hershey and chase created phages with radioactive protein and phages with radioactive DNA. Which one resulted in radioactive bacteria? Why?
DNA
it functions as the genetic material of phage t2
What year did Watson crick publish their structure for DNA
1953
Chargoffs rule
A=t
C=g
Two strands of DNA w double helix and sugar-phosphate backbone
See chapter notes
Nucleotide pairs
C & G
A & T
DNA is replicated by base pairing to a template strand. If you missed class and copied your friends notes, who’s notes are acting as a template?
The friends
In a new DNA molecule ___ of the new double helix is made up of nucleotides from the previously existing molecule
Half
DNA replication can only begin at particular called
Origins of replication
Diagram of replication fork
See chapter notes
Unwinds and pulls apart the 2 DNA strands
Helicase
Prevents over winding
Topi isomerism
Builds primer (short RNA sequence to begin new strand)
Promise
Adds DNA nucleotides to 3’ end of growing strand
DNA polymerase
DNA polymerase can only add nucleotides to an existing chain, so in order to initiate replication it requires a short chain of RNA called
Primer
Bc of the antiparallel structure of DNA, each single strand has a 3’ end a
5’ end
DNA polymerase can only add nucleotides to the ___ end of the growing new strand
3’
Elongation occurs in the direction away from the ___ end of the template strand and towards the ____ end of the template strand
5’
3’
The lagging strand cannot be but in one continuous piece, and must be pieces together as a series of segments called
Okazaki fragments
Each of these segments begins with a ____ made of RNA
Primer
A primer is eventually replaced with DNA by the enzyme ____
DNA polymerase
The segments are joined together into a continuous strand by the enzyme
DNA ligase
Mechanisms for minimizing errors in DNA replication
Proofreading by the enzyme DNA polymerase during replication
Removal and replacement of incorrect nucleotides during replication, in a process know as mismatch repair
Removal of a damaged DNA strand after replication is complete by the enzyme nuclease
The 5’ end of the lagging strand consists of a primer made of
RNA
This primer cannot be replaced because DNA polymerase ____ add nucleotides to the 5’ end of the strands
Cannot
With each replication, a linear chromosome becomes
Shorter
The end of each of our chromosomes consists of a chunk of nonsense DNA known as
Telomeres
In germ cells (cells that produce egg and sperm) this nonsense DNA is lengthened by the enzyme
Telomerase
What would happen if you had no telomerase in your germ cells?
Babies would be born w no telomeres - would be born already old
What would happen if you had telomeres in all of your cells?
More susceptible to cancer
