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An entire DNA molecules
Segment of DNA(or RNA in some viruses) that encodes a functional product, usually a protein
all of the genetic material in a cell/organism
Study of what genes are, how hthey carry information....
Molecular study of genomes
expression of the genes. ex. Genotype fo hari color DNA. Phenotype -the color you see(appearence for what the gene for)
DNA helicase unwinds creating a replication fork.
Coping of DNA
- Leading strand - Synthesized continuosly as DNA polymerase (copies DNA) moves in one direction towards the repication fork.
- Lagging strand - DNA synthesized in pieces as the DNA polymerase moves away from the replication fork. RNA primer(synthesiezed by RNA polymerase) starts the synthesis, than DNA polymerease chews up RNA primer and replace it with DNA, than DNA ligase joints the okazaki fragments together
DNA replication is semiconservative
becuase each new DNA molecule contains a single parental strand and one new strand.
Energy bonds within necleotides
- Nucleotids themsleves provide the energy
- Unbound necleotides are - necleoside triphosphates, cleaving of one phospate releases energy.
DNA Replication of Bacteria
is bidirectional around the chromosome
DNA is trascribed to mRNA, tRNA, rRNA
Transciription of mRNA
- Using single strand DNA as a tamplet(a signle gene)
- Begines when RNA polymerase binds to the promotor sequence on the DNA helix and the unwinds the strands. One strand serves as a template and complementory base pairing begins Uracil instead of Thymine. Trascription stops when RNA polymerase reaches the terminator sequence. mRNA and RNA polymerease are released and DNA helix rewinds.
Direct source of information for protein synthesis. mRNA act as an intermediate between the permanent storage form, DNA, and translation
- mRNA is translated in block called codons (3 necleotides)
- Translation of mRNA begins at the start codon AUG.
- Ends at a stop (nonsence) codon: UAA, UAG, UGA
- Translation is facilitated by the ribosomes
- tRNA molecuels recognize the codons, each carries a spacific individual amino acid.
- each tRNA has a reagine called anticodon - complimantory to a spacific codon on the mRNA.
- directs the orderly binding of tRNAs to the codons and assembles the polypeptide chain.
- Multiple mibosomes can be trnslating the same mRNA molecules at the same time.
- in Prokayorotes, translation can begin even before trancription is complete.
Degenerasy of the code
multiple codons specify the same amino acid.
RNA processing in Eukaryotes
- Genes of eyukaryotic DNA contain introns and exons.
- Only exons code for proteins
- mRNA transcript contains the same introsn and exons as the DNA.
- Ribozymes remove the introns from the mRNA tnrascript and put together the exons - creating a functional mRNA that leaves the nucleus for translation in cytoplasm.
- Ribozymes - are like enzyme but made of RNA and act on RNA.
- inhibits transcription of DNA
- Repressor proteins block RNA polymerase from initiation trancription.
Inducers turn on the trascription process of a gene.
are expressed at a fixed rate.
Operon model of Gene expression
- Francois Jacob and Jacques Monod (1961)
- Operon - (P, O and stractural genes) a region of DNA in a bacterium where the genes responsible for coding for protein/enzymes and found together one after the other.
- Control region of ooperon - Promoter (where RNA pollymerase binds), Operator(where repressor proteins binds )
- Near the beginning of the lac opoeron is a regularotry gene (lac I) that codes for the production fo a repressor protein
- When no lactose present, repressor protein binds to operator and this blockes RNA polymerase from binding to promotor for trasncription.
- When lactose is present, lactose in converted into indcuser that binds to repressor protein which changes tha shape of the protein that can no longer binds to operator.
neither benefit nor damage the organism
could lead to antibiotic resistance or altered pathogenecity
lead to loss of function, the formation of a cener, or death.
Types of mutation
- Base substitution
- Nonsense mutation
- Frameshift mutation
- Spontaneous mutation
Base subsisution (point mutation)
a single base is replaced with a different base. Base subsitution occures whin in a gene that codes for a protein. When base subsitution results in an amino acid subsitution in the synthesized protein , this cahnge in the DNA is known as a missense mutation.
Creates a stop codonin th mRNA molecules that will prevent the synthesisi of a complete functional protein.
Nucleotide pairs are deleted or inserted in the DNA that can shift the translation reading frame.
occur in the absence of a mutagen, and is due to a mistake in the DNA copying process.
- Mutagen - agent that causes mutation
- 1. Chemical mutagesn
- 2. Radiation
- a. Ionizing radiation
- b. UV radiation
xrays, gamma rays, casue the foratmion of ion and free radical s that can react with nucleotides and backbone.
- casues bonds to form between adjacent pyrimidine bases, usually thymines, formiing thymine dimers.
- Light-repair enzymes can separate thymine dimers.
- Nucleotide excision reapiar mutatuion by cuttiong out and replacint the damaged stretch of DNA
Identifying mutants by direct selection
decets mutant cells becuase they grow or appear differently
Identifying mutants by indirect selection
- detects mutant cells becuase they do not grow
- auxotrophs - mutatnt cells that have a nutrtitional requirement
- Exchange of genes wetween two DNA molecules to from new combination fo genes on a chromosome.
- Crossing over
- Recombination - more beneficial than mutation.
Vertical gene trasfer
genes are passed from parent cell to a daugher cell
Horizontal gene trasnfer
- When genes are passed from one adult cell to another
- Donor cell give a portion to its DNA to a recipient cell - recombinant cell
Gene trasnfer by Transformation in bacteria
when a cell lysis, its DNA released and other cells take up fragment
Conjugation in Bacteria
- involves a plasmi - small circular piece of DNA that replicates independently from the cell's chromosome.
- in G - species, plasmid carry genes for sex pili
- in G +, sticky surface brin cell together.
Transduction in bacteria
DNA is transfered from cell to cell by virus
carries genes for sex pili and transfer of the plasmid
catabolism of unusual compounds, ex. petroleum
Resistance (R) Factors
encode resistance to antibiotics, heavy metals, or cellular toxins.
- Segments of DNA that can move from one region of a DNA to another.
- Consist of insertions for cuttion and resealing DNA