Gene
segment of DNA encoding a functional product
DNA polymerase
Enzyme used in DNA replication- synthesizes DNA by copying a DNA template
DNA ligase
Enzyme used in DNA replication - covalently bonds a carbon atom of one nucleotide with the phosphate of another nucleotide
Genome
the total genetic material/information of a cell (contains Chromosomes & plasmids)
Structure of DNA
double helix with backbones of deoxyribose + phosphates and base pairs (A-T, C-G) held together by hydrogen bonds
Structure of RNA
similar to DNA but consists of only one chain or strand of bases. The sugar in RNA is ribose not deoxyribose. the base thymine is replaced by uracil and RNA is involved in protein synthesis
complimentary base pairing
hydrogen bonding between particular bases; in DNA, thymine (T) pairs with adenine (A), and guanine (G) pairs with cytosine (C); in RNA, uracil (U) pairs with A, and G pairs with C
DNA template
a strand of DNA used to make either DNA or mRNA
-RNA polymerase uses it to link together RNA nucleotides during transcription
Transcription
the process of synthesizing RNA from a DNA template
Translation
The use of mRNA as a template in the synthesis of protein
Triplet code
the normal version of the genetic code in which a sequence of three nucleotides codes for the synthesis of a specific amino acid
Codon
a specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid
Stop Codon
AKA nonsense codon
UAG, UAA, or UGA; the codon that ends all RNA.
Start Codon
AUG; the codon that begins all RNA.
RNA polymerase
an enzyme that hooks together the RNA nucleotides as they base pair along the DNA template
Interons
intervening sequences of bases within genes that are not part of a code for a protein
Exons
expressed sequence of DNA; codes for a protein
anticodon
A sequence of three bases of a tRNA molecule that pairs with the complementary three-nucleotide codon of an mRNA molecule during protein synthesis.
ribosome
site of protein synthesis (translation)
Moves along mRNA (in the 5'-->3' direction) receiving Amino Acids from tRNA producing a polypeptide chain
Genotype
genetic makeup of an organism (potential properties)
phenotype
expressed physical characteristics of an organism (actual properties)
(the manifestation of genotype)
gene expression
conversion of the information encoded in a gene first into messenger RNA and then to a protein
constitutive enzymes
Produced at a fixed rate, ie enymes for glycolysis
inducible enzymes
their synthesis is induced by a chemical signal (allolactose for lac operon), function in catabolic pathways
repression gene
Repressor binds to DNA and prevents transcription. repressor protein binds to operator (near promoter). prevents transcription process from occurring (blocks path of RNA polymerase)
induction gene
Inducer 'turns on' transcription. binds to/changes shape of repressor. repressor can't bind to operator, transcription occurs.
Structural genes
Produce an RNA molecule that contains the information needed to specify a polypeptide with a specific amino acid sequence
regulatory genes
guide the expression of structural genes, without coding for a protein themselves.
promoter
the region of DNA where RNA polymerase initiates transcription
operator
acts like a traffic light signaling the stop and go of transcription
repressor
blocks the ability of RNA polymerase to initiate transcription from the repressed genes
Operon
a set of operator and promoter sites and the genes they control
LAC operon
a gene with a promoter, an operator gene, and three structural genes that control lactose metabolism
allolactose Inducer
If lactose is present, this isomer of lactose depresses the operon by inactivating the repressor, inducing the enzymes for lactose utilization
inducer
A specific small molecule that inactivates the repressor in an operon thus inducing transcription
catabolic repression/glucose effect
system of gene regulation in which the presence of the preferred energy source represses other catabolic pathways
mutation
change in a DNA sequence that affects genetic information
genetic recombination
major source of genetic variation among organisms caused by reassortment or crossing over during meiosis
transformation
1st method of DNA transfer
the transfer of "naked" genetic material in the form of DNA fragments from one cell to another or from one organism to another
Conjugation (mating types)
2nd method of DNA transfer
Different from "transformation"
Cells must be opposite mating types with the donor carrying PLASMID (AND direct contact)
G- gene to form Sex Pilus
G+ gene to produce sticky surface for contact
F Factor/fertility factor
The first plasmid to be transfered
Donors with F Factor called "F+ cells
Hfr (High Frequency Recombination)
F factor is integrated INTO the chromosome
Transduction
3rd method of DNA transfer (generalized-any gene and Specialized-Certain gene)
Transfered by bacteriphages
4 steps
1 - Attach (adsorption)
2 - Insertion
3 - Assembly
4 - Release
Conjugative Plasmid
Plasmid that carries the genes for sex pili and can transfer copies of itself to other bacteria during conjugation.
Dissimilation plasmid
encode enzymes for catabolism of unusual compounds
Transposons
(jumping genes) short strands of DNA capable of moving from one location to another within a cell's genetic material
Complex transposons
Segments of DNA that carry other genes in addition to transposase genes
Simple transposons
Contain INSERTION SEQUENCES for TRANSPOSASE to cell and reseal DNA. Concerned only with transposition process.
Restriction Enzymes
enzyme that cuts DNA at a specific sequence of nucleotides
Prototroph
a microorganism that has no requirements for organic growth factors because it can synthesize them.
Auxotroph
an organism that requires supplementary nutrition because of a genetic defect
3' (3 prime)
The end of DNA that has a hydroxyl attached to the 3' carbon (of sugar)
DNA polymerase can only add new nucleotides to this end
5' (5 prime)
The end of DNA that has a phosphate attached to the 5' carbon (of sugar)
The order that DNA strands fit together
5' ---> 3'
plasmid
small circular DNA molecule that self replicates independently of the chromosome
R Factors
Plasmid encodes antibiotic resistance
Pathogeneticity plasmids
code for toxin production