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60 terms

Biology II- Genetics (cont.)

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Extranuclear genes
genes outside the nucleus; located in mitochondria and chloroplast
1952
Hershey and chase did an experiment on viruses where they could tell that DNA is the genetic material in cells and not protein
1953
Watson, Crick, Franklin and Wilkins write about the structure of DNA; received the Nobel Prize in 1960
Nucleic acid (DNA)
made form nucleotides which are constructed from phosphate, sugar and nitrogenous bases (A,T, G, C)
DNA
has a phosphate, sugar backbone double stranded rung shaped base, and is twisted into a helix
strands held together by weak bonds of hydrogen bases
Bases are made of purines
2 rings made of Adenine(A) and Guanine(G)
Bases are made of pyrimidines
1 ring made of Thymine(T) and Cytosine(C)
Base pairings
A-T, G-C; 5 prime end has free phosphates; 3 prime end has sugar; replication is always ordered as '5' before '3'
DNA replication
DNA is unwound and replication happens in both directions; happens during the S phase
replication fork
DNA separation point
RNA polymerase
makes RNA molecules; protein involved in DNA replication
DNA polymerase
makes DNA molecules
Primase
makes primer; An enzyme that joins RNA nucleotides to make the primer.
Helicase
unwinds the double helix
Single strand binding
proteins that stabilize the unwound DNA
Anti parallel
the strands of DNA go in opposite directions; 5 prime end matches with 3 prime end
Primer formation
primase (RNA polymerase) makes a short strand of RNA primer to help the building of the DNA copy
Elongation
nucleoside triphosphate creates and attaches appropriate base by using DNA polymerase
Leading strand
the top strand of original DNA; a simple process of laying down a primer and DNA polymer which houses up appropriate nucleotides
DNA is then built
Lagging strand
DNA strand built in the opposite direction
it creates a section then leaps to the other end to finish
Onizaki fragments
has multiple primers to create DNA
After Elongation
the primers (RNA) is removed and replaced by DNA polymerase; gap left from RNA replacement so DNA ligase stitches the fragments together
DNA repair: Nuclease
removes damaged or incorrect nucleotide
DNA repair: DNA polymerase
replaces the removed and damaged DNA
DNA repair: DNA ligase
knits the new DNA to the existing DNA
Telomeres
non-coding DNA strands at the end of chromosomes( not part of gene) protects chromosomes from deterioration
Protein Synthesis
the change from genes(DNA) to proteins
Transcription: first step to Protein Synthesis
the making of a messenger RNA(mRNA) form a DNA template
takes place in the nucleus and makes a pre-mRNA
Translation: second step to Protein Synthesis
makes a polypeptide chain from a mRNA template
changes a nucleotide code into a polypeptide code
takes place at the ribosome in the cytoplasm
polypeptide
a long chain of amino acids
Transcription and Translation
this mRNA processing makes the real mRNA
RNA bases
Adenine, Guanine, Cytosine, Uracil
Transcription makes
strands of RNA that are complementary to the DNA bases
RNA is translated from
codons(sequence of 3 nucleotides [Amino acid codes]) to amino acids
First stage: Transcription in prokaryotes-Initiation
Promoter-DNA sequence that signals the start of transcription
RNA polymerase binds to the promoter, it then unwinds the DNA
Second stage: Transcription in prokaryotes- Elongation
RNA polymerase adds nucleotides (A, G, U, C); continues to unwind DNA; Builds the RNA in the 5 prime-3prime pattern; no primers are needed for the process; makes many mRNA's on one DNA strand
Last stage: Transcription in prokaryotes- Termination
the DNA sequence polymerase drops off, then the creation of the mRNA is done
Transcription in eukaryotes- Initiation
Transcription factors are necessary to RNA polymerase to bind to promoters
i.e. TATA Box, Transcription Initiation Complex
TATA Box transition factor
DNA promoter sequence
Transcription Initiation Complex
RNA polymerase and Transcription factors attach to this
Transcription in eukaryotes- Elongation
has more than one type of RNA polymerase
Transcription in eukaryotes- Termination
polyadenylation signal- DNA sequence that ends transcription
is code for many A's (adenines) in a row
the RNA is cut from the polymerase and becomes pre-mRNA
RNA processing
alternations of the ends of the pre-mRNA
5prime end has '5' cap added for modified G nucleotide
3 prime end has a poly-A tail added to it; sometimes has hundreds of Adenine nucleotides
RNA splicing
the cut and paste of RNA molecules
RNA and DNA are non-coding
meaning they will not be translated to proteins
introns
non-coding RNA ends
exons
coded RNA ends
Alternative splicing
one gene can have a piece of many different polypeptides
mRNA
messenger RNA made during transcription and used during translation
tRNA
transfer RNA; has amino acid binding site on one end and anti-codon on the other end; brings amino acids to the polypeptide
rRNA
ribosomal RNA; makes up the ribosome
Aminoacyl tRNA synthase
the attachment of an amino acid to the RNA with the assistance of ATP and enzymes; is a tRNA wit an amino acid attached to it
Ribosomes
enzymes that have two sub-units; a large sub-unit and a small sub-unit; each has a binding site; the large and small sub-units stay separate until translation begins
Ribosome large sub-units
has three binding sites; A-aminoacyl tRNA, P-peptidyl tRNA, E-exit
Ribosomes small sub-unit
has a binding site fro mRNA
Translation- Initiation
the mRNA, tRNA, and both ribosomal units come together; creates a translation initiation complex
initiator tRNA
binds to a "start" codon (AUG) and always methionine
Translation- Elongation
amino acids are added to the mRNA chain one by one
A new tRNA binds to the A-site of the ribosomal, the amino acid binds to the chain in the P-site, the tRNA moves to the next site, and the old tRNA is kicked off; this process goes in one direction
Translation- Termination
stop codon(UAG, UAA, or UGA) begins at this point; the release factor binds to the stop codons and the whole translation initiation complex falls apart
Modification to polypeptides
folding occurs; some things may be added or removed from the chain; some polypeptides are targeted for specific locations; polypeptide initiates binding of ribosomes to Rough ER; polypeptide then ends up in ER