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Micobiology Test #4 unit 5 terms
Terms in this set (49)
Central dogma of molecular biology
main principle of molecular biology that follows DNA to RNA and RNA to protein. It also involves DNA replication.
an ordered and regulated process that involves the duplication of a cell's genome.
process that involves using information in DNA to create a protein. This process requires transcription and translation.
synthesis of mRNA using a DNA template.
1. Synthesis of a protein using an mRNA template
2. Translation is the final step in expression of protein encoding genes mRNA sequence is converted into amino acid sequence of polypeptide chain
the entirety of an organism's hereditary information;
refers to all the DNA present in a cell or virus
the monomeric units of nucleic acids.
3 parts to a nucleotide
3. Nitrogenous base
A heterocyclic ring structure with varying functional groups. The purines adenine and guanine are found in both DNA and RNA.
A heterocyclic six-membered ring structure. Cytosine and uracil are the main pyrimidines found in RNA, and cytosine and thymine are the main pyrimidines found in DNA.
Synthesis is semi-conservative
each daughter cell obtains one old and one new strand
Origin of replication
a particular sequence in the genome where replication is first initiated. (sequence of DNA)
the place at which the DNA helix is unwound and individual strands are replicated.
Two replication forks move away from origin of replication...bidirectional synthesis
-uses ATP to break the hydrogen bonds between complementary base pairs.
-enzyme that breaks hydrogen bonds, splitting double stranded DNA
look over slide 17
-catalyzes synthesis of complementary strand of DNA;
-DNA synthesis is in 5' to 3' direction resulting with the formation of a phosphodiester bond.
-an enzyme that synthesizes DNA using dNTPs (D= deoxy) (N= any of the 4 nitrogenous bases) (T= triple P) (P= phosphate)
bind single stranded DNA
-A protein complex that replicates DNA to form 2 daughter double helices
-complex of many different proteins which are recruited to the origin of replication
-nick the DNA to relieve coiling tension
-reduces tension in chromosome by breaking phosphodiester bond, release tension, reform bond
Location of the phosphodiester bond
3'5'----3'5'this bond is a phosphodiester bond- covalently bonded
3'5'-----3'5' there are hydrogen bonds between the two- hydrogen bonded and not covalently bonded
DNA polymerase III
A holoenzyme that is a complex of 10 proteins with two core
enzymes - one for each parental strand.
Removal of mismatched base from 3' end of growing strand by
exonuclease activity of enzyme
This activity is not 100% efficient
Get's its energy from the triphosphate bond of the dNTPs
-DNA dependent RNA polymerase
-Does not need a 3' end to add nucleotides to
-RNA polymerase synthesizes RNA primer so that DNA polymerase 3 can work
A short segment of single-stranded DNA that is an intermediate in DNA synthesis. In bacteria, Okazaki fragments are 1000-2000 bases in length; in eukaryotes, 100-200 bases in length.
Explain synthesis....then ask, How do you get the RNA out?
DNA polymerase I has a 5' to 3' exonuclease activity...this is opposite from DNA polymerase III.
DNA ligase forms a phosphodiester bond between 3'-hydroxyl of the growing strand and the 5'-phosphate of an Okazaki fragment
Process of DNA replication
1. DNA synthesis begins at the origin of replication.
2. Loading of the replisome and breaking the H bonds between base pairs requires ATP consumption.
3. DNA polymerase brings in the appropriate dNTP to make Watson-Crick base pairs to template strand
4. Synthesis of the new strand occurs in the 5' to 3' direction.
5. Reading of the template occurs in the 3' to 5' direction.
Telomerase start of test 5
1. has a protein that can synthesize DNA using an RNA template (reverse transcriptase)
2. an internal RNA template thus solving the "end replication problem
the basic unit of genetic information; also defined as the nucleic
acid sequence that codes for a polypeptide, tRNA or rRNA
linear sequence of nucleotides with a fixed start point and end
one RNA contains info of several genes
mRNA only codes for one polypeptide/ gene
a way of breaking a sequence of nucleotides in DNA or RNA into three letter codons which can be translated in amino acids.
has the same sequence as the RNA produced
directs RNA synthesis ...complementary to RNA
is read in the 3' to 5' direction
-is located at the start of the gene
-is the recognition/binding site for RNA polymerase
-functions to orient polymerase...it is NOT transcribed
-Influences when a gene is transcribed
transcribed into mRNA but is NOT translated into amino acids
Also known as the 5'UTR
procaryotic sequence important for initiation of translation
proposed by Australian scientists John Shine and Lynn Dalgarno
ribosomal binding site generally located 6-7 nucleotides upstream of the start codon AUG.
The six-base consensus sequence is AGGAGG; in E. coli, for example, the sequence is AGGAGGA.
This sequence helps recruit the ribosome to the mRNA to initiate protein synthesis by aligning it with the start codon. The complementary sequence (CCUCCU), is called the anti-Shine-Dalgarno sequence and is located at the 3' end of the 16S rRNA in the ribosome.
begins with the DNA sequence 3'-TAC-5'
produces codon AUG (start codon)
codes for N-formylmethionine, a modified amino acid used to initiate protein synthesis in bacteria
coding region ends with a stop codon
immediately followed by the trailer sequence which contains a terminator sequence used to stop transcription
the process by which RNA is produced by the enzyme RNA polymerase using DNA as a template.
1. Initiation: Unwinding of DNA and attachment of RNA polymerase at the promoter site.
2. Elongation: Synthesis of RNA by RNA polymerase.
3. Termination: Synthesis ends at a terminator site.
-Five polypeptide unit that catalyzes the formation of RNA
-Clamps around the DNA and RNA
-Initiation begins: when RNA pol binds to promoter
only a short segment of DNA is transcribed before initiation is considered complete
an additional protein unit (sigma factor) helps the core enzyme to recognize the start of genes (sigma has no catalytic activity).
As the polymerase elongates, the sigma factor will dissociate
Triphosphate ribonucleotides align with their DNA complements and RNApolymerase links them together, synthesizing RNA. No primer is needed. Thetriphosphate ribonucleotides also provide the energy required for RNA synthesis.
After binding, RNA polymerase unwinds the DNA...does NOT need a helicase.
Transcription does not start at the promoter...rather several nucleotides downstream of it.
Transcription bubble produced
Moves with the polymerase as it transcribes mRNA from template strand
Within the bubble a temporary RNA:DNA hybrid is formed
Reaction catalyzed by RNA polymerase
Pyrophosphate is cleaved in two so that the reaction does not occur in the reverse reaction.
Sequences in the trailer signal the RNA polymerase to be done.
When transcribed into RNA, the form hydrogen bonds within the single-stranded RNA and creates a secondary structure that slows the polymerase
Terminator sequence produces an RNA that folds on itself. Loosening the grip of polymerase on DNA. A GC rich terminator sequence...tougher for RNA polymerase to separate dsDNA.
binds to mRNA and moves toward RNA polymerase and pushes polymerase away from DNA
Summary of Steps in Transcription
see slide 46
The sequence of DNA nucleotides that determines the amino acid sequence of the translated protein. The genetic code is `read' in triplets of bases called codons.
up to six different codons can code for a single amino acid
Normally 20 amino acids are present...but there are 64 possible codons
the 61 codons that specify amino acids
Stop (nonsense) codons
the three codons used as translation termination signals
do not encode amino acids
start onn slide 53
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