DNA/RNA Flashcards
What were the results for the mice injections in the Griffith Experiment?
live pathogenic strain=mice die
live nonpathogenic strain (no protein coat)=mice live
heat-killed pathogenic strain=mice live
mix of heat-killed pathogenic and nonpathogenic strains=mice died
What is transformation?
the transfer of genetic material from one cell to another which can alter the genetic makeup of the recipient cell
What is a bacteriophage?
a virus that attacks bacteria
What is a purine?
a base-double carbon ring. Adenine and Guanine
What is pyrimidine?
base-single carbon ring. Cytosine, thymine (uracil in RNA)
phosphodiester bond
holds sugars to phosphates on the sides of the DNA (RNA)
hydrogen bond
holds the bases together to make the “rings” of the DNA ladder
Chargaff’s Rule
A’s pair with T’s; G pairs with C’s
There is always an equal portion of A’s to T’s and of G’s to C’s. A:T and G:C
The base pairing is also known as being complementary
semiconservative replication
the way DNA actually copies itself. copying genetic information is complementary
DNA unzips- one side serves as the template for the new strand being built
Conservative Replication
parent DNA stays intact and makes new copies of DNA
Dispersive Replication
parent DNA is dispersed throughout new DNA so each strand is a mix of old and new
What are the three things that replication requires?
something to copy-parental DNA molecules serve as a template
something to do the copying-enzymes
building blocks-nucleotides
Where does replication begin?
replication forks
What enzyme glues new nucleotides to the growing strands
DNA polmerase 3
What is the RNA primer
the anchor. the enzyme RNA primase builds a piece of RNA primer about 10 RNA nucleotides long. DNA Polymerase 3 recognizes the primer and starts to build new DNA strand
leading strand
the DNA strand elongating toward the replication fork
continuous replication
new DNA is built continuously by simply adding nucleotides to the 3 end
lagging strand
the DNA strand elongating away from the replication fork
discontinuous replication
new DNA is built in pieces
Okazaki Fragments
segments of DNA about 100-20 nucleotides long
What unwinds the DNA
helicase
how are DNA strands kept open?
single-strand binding proteins
DNA polymerase 1
removes primers and fills in gaps between Okazaki fragments
DNA Ligase
rejoins the parent strand
DNA Gyrase
releases tension in the DNA
Primosome
composed of primase and helicase and accessory proteins
Describe the Griffith Experiment
Griffith was trying to make a vaccine against the flu which was thought at the time to be caused by a bacterium called Streptococcus pneumoniae
The bacteria comes in two forms:
virulent (disease causing), makes deadly polysaccharide coat that causes blood poisoning
-“S” form
nonvirulent- no polysaccharide coat
-“R” form (shouldn’t kill)
rRNA
ribosomal RNA- makes up ribosomes and provides a place to make proteins
mRNA
messenger RNA- long piece of RNA transcriped/made from DNA
-a “xerox” copy of a gene which leaves the nucleus and goes to a ribosome to direct the making of a protein.
copies genes in the nucleus and takes it to the ribosome in the cytoplasm so it takes it out of the nucleus
Codons
genetic information exists in blocks of genetic information
Nonsense Codons
code for nothing
reading frame
the order in which the nucleotides of DNA are read
Transcription
- 1st phase of gene expression
- when a sequence (piece) of DNA is transcribed into a mRNA sequence (piece)
- RNA polymerase- the enzyme that starts transcription
How does transcription happen?
RNA polymerase binds to a special binding site (PROMOTOR)
RNA polymerase moves along the DNA strand into the gene
as it encounters each DNA nucelotide, it adds the corresponding complimentary RNA nucleotide to the growing mRNA copy
RNA polymerase arrives at a stop signal at the end of the gene and drops off the DNA
new mRNA is released
Initiation
start reading the mRNA copy
elongation
bring amino acids to the protein chain and make it grow
termination
release the protein from the ribosome
What is the process of translation?
rRNA molecule binds to “START” codon of mRNA
ribosome moves along mRNA, 3 nucleotides (1 codon) at a time
tRNA gets its amino acid attached to it by protein
tRNA’s add their amino acids to growing protein chain
ribosome goes until it encounters a STOP codon
ribosome drops off of mRNA and releases the completed protein
What does translation start with
the formation of an initiation complex
What is the elongation process?
Ribosome exposes codon next to the start codon
the tRNA carrying the corresponding amino acid binds its ANTICODON with the mRNA’s codon with help of proteins called ELONGATION FACTORS
The ribosomes rolls and exposed the next codon. The met-tRNA is in the old A SITE which is now called the P SITE. The newly exposed codon is in the A site.
THe tRNA that matches the new exposed codon brings in its amino acid.
Met joins to the newly added amino acid via a PEPTIDE BOND and its released from its tRNA
Process repeats. Old P site is now an E site (empty) old a site is now the p site. new codon is exposed in the a site
this continues, ribosomes moves along ribosome, exposing 3 nucleotides at a time (TRANSLOCATION)
How are stop codons recognized?
proteins called release factors
