DNA replication
the process of making a copy of DNA
semiconservative replication
DNA replication in which each of the parental strands is read to make a complementary daughter strand, ethus each new DNa molecule is composed of half the parental molecule paired with a newly synthesized strand.
helicase
an enzyme that untwists the double helix at the replication forks, separating the two parental strands and making them available as template strands
replication fork
A Y-shaped region on a replicating DNA molecule where new strands are growing.
single strand binding protein
During DNA replication, molecules that line up along the unpaired DNA strands, holding them apart while the DNA strands serve as templates for the synthesis of complementary strands of DNA.
topoisomerase
A protein that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.
dna polymerase
enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule
antiparallel
Parallel, but running in opposite directions. The 5' end of one strand of DNA aligns with the 3' end of the other strand in a double-helix.
DNA ligase
an enzyme that eventually joins the sugar-phosphate backbones of the Okazaki fragments
Okazaki fragments
Short fragments of DNA that are a result of the synthesis of the lagging strand during DNA replication.
lagging strand
A discontinuously synthesized DNA strand that elongates in a direction away from the replication fork.
primase
An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.
RNA primer
Sequence of RNA primers bound to a region of single-stranded DNA to initiate DNA replication.
Telomeres
The protective structure at each end of a eukaryotic chromosome. Specifically, the tandemly repetitive DNA at the end of the chromosome's DNA molecule. See also repetitive DNA.
gene
(genetics) a segment of DNA that is involved in producing a polypeptide chain
genotype
the particular alleles at specified loci present in an organism
one-gene-one-enzyme hypothesis
Hypothesis of Beadle and Tatum that one gene controls the production of one enzyme. Later modified to the concept that one cistron controls the production of one polypeptide
one-gene-one-polypeptide hypothesis
The premise that a gene is a segment of DNA that codes for one polypeptide.
one-gene-one-protein hypothesis
the genetic info contained in one gene of a DNA molecule isused to make one molecule of mRNA by transcription; the genetic info in that mRNA molecule is then used to make one protein by translation
protein synthesis
the formation of proteins by using information contained in DNA and carried by mRNA
transcription
(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA
RNA processing
Modification of RNA before it leaves the nucleus, a process unique to eukaryotes.
translation
(genetics) the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm
mRNA
messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome
tRNA
short-chain RNA molecules present in the cell (in at least 20 varieties, each variety capable of combining with a specific amino acid) that attach the correct amino acid to the protein chain that is being synthesized at the ribosome of the cell (according
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
genetic code
the ordering of nucleotides in DNA molecules that carries the genetic information in living cells
anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
wobble
A violation of the base-pairing rules in that the third nucleotide (5' end) of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon.
rRNA
ribosomal RNA; type of RNA that makes up part of the ribosome
initiation
DNA replication is initiated when helicase enzyme breaks the hydrogen bonds holding the base pairs together and the DNA uncoils.
elongation
addition of amino acids to the polypeptide chain; continues until it reaches a stop codon
termination
the ribosome reaches a stop codon on the mRNA and protein synthesis stops.
promoter region
A regulatory region a short distance upstream from the 5' end of a transcription start site that acts as the binding site for RNA polymerase. A region of DNA to which RNA polymerase binds in order to initiate transcription.
5' cap
a modified guanosine and triphosphate cap is added to the 5' end, helps protect the mRNA from degradation by hydrolytic enzymes, and functions as an "attach here" sign for ribosomes
poly-A tail
A string of adenine nucleotides at the 3' end of most mature eukaryotic mRNAs; causes a eukaryotic mRNA to be more stable; added enzymatically after a pre-mRNA has been completely transcribed
RNA splicing
process by which the introns are removed from RNA transcripts and the remaining exons are joined together
exons
expressed sequence of DNA; codes for a protein
introns
a non-coding, intervening sequence within a eukaryotic gene
snRNP's
bind to introns and remove them by forming splicosomes, splicing exons together
Alternative splicing
a type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns
aminoacyl-tRNA
A tRNA with an amino acid attached. This is made by an animoacyl-tRNA synthetase specific to the amino acid being attached
GTP
A nucleotide composed of guanine, ribose, and three linked phosphate groups. It is incorporated into the growing RNA chain during synthesis of RNA and used as a source of energy during synthesis of proteins
translocation
the movement of a segment of DNA from one chromosome to another, which results in a change in the position of the segment; also the movement of soluble nutrients from one part of a plant to another
A site
One of a ribosome's three binding sites for tRNA during translation. This site in the ribosome holds the tRNA carrying the next amino acid to be added to the polypeptide chain.
P site
one of a ribosome's three binding sites for tRNA during translation. It holds the tRNA carrying the growing polypeptide chain.
E site
One of a ribosome's three binding sites for tRNA during translation. This site is the place where discharged tRNAs leave the ribosome.
Point mutation
mutation that affects a single nucleotide, usually by substituting one nucleotide for another
substitution
a mutation in which a nucleotide or a codon in DNA is replaced with a different nucleotide
deletion
the loss of one or more nucleotides from a gene by mutation; the loss of a fragment of a chromosome.
insertion
A mutation involving the addition of one or more nucleotide pairs to a gene.
frameshift
a deletion or insertion of base pairs which alters the reading of the frame (3 at time), producing different amino acids
mutation
(genetics) any event that changes genetic structure
silent mutation
A mutation that changes a single nucleotide, but does not change the amino acid created.
missense mutation
The most common type of mutation, a base-pair substitution in which the new codon makes sense in that it still codes for an amino acid.
nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
mutagens
Factors in the environment that cause mutations.
carcinogens
substances that cause cancer
proofreading
the process by which DNA polymerase corrects its own errors as it moves along DNA.
mismatch repair
The cellular process that uses special enzymes to fix incorrectly paired nucleotides.
excision repair
The process of removing and then correctly replacing a damaged segment of DNA using the undamaged strand as a guide.
chromatin
the readily stainable substance of a cell nucleus consisting of DNA and RNA and various proteins
histone
protein molecule around which DNA is tightly coiled in chromatin
nucleosomes
bead-like structures formed by histones and DNA
euchromatin
a region of DNA that is uncoiled and undergoing active transcription into RNA
heterochromatin
Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.
transposons
(jumping genes) short strands of DNA capable of moving from one location to another within a cell's genetic material
bacteriophages
viruses that infect bacteria
capsid
the outer covering of protein surrounding the nucleic acid of a virus
envelope
a membranelike layer that covers the capsids of some viruses
lytic cycle
a viral reproductive cycle in which copies of a virus are made within a host cell, which then bursts open, releasing new viruses
retroviruses
An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.
reverse transcriptase
a polymerase that catalyzes the formation of DNA using RNA as a template
lysogenic cycle
a viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA
provirus
viral DNA that has attached to a host cell's chromosome and that is replicated with the chromosome's DNA
binary fission
a form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size
plasmids
The smalll, circular segments of DNA that are found in bacteria and that stay sparate from the bacterial chromosomes; used in genetic engineering.
episomes
A genetic element in bacteria that can replicate free in the cytoplasm (has a different number of copies) or can be inserted into the main bacterial chromosome and replicate with the chromosome. Plasmids are an example.
conjugation
the process by which two prokaryotes bind together and one cell transfers DNA to the other cell through a structure called a sex pilus
pili
short, hairlike protein structures on the surface of some bacteria
F plasmid
cells that contain this function as DNA donors during conjugation; F+ cells transfer DNA to F- recipients; chromosomal genes can be transferred during conjugation when donor cell's F factor is integrated into chromosome
R plasmid
A bacterial plasmid that carries genes for enzymes that destroy particular antibiotics, thus making the bacterium resistant to the antibiotics
transduction
(genetics) the process of transfering genetic material from one cell to another by a plasmid or bacteriophage
transformation
(genetics) modification of a cell or bacterium by the uptake and incorporation of exogenous DNA
operon
a segment of DNA containing adjacent genes including structural genes and an operator gene and a regulatory gene
promoter
A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA.
operator
region of chromosome in an operon to which the repressor binds when the operon is "turned off
structural genes
Produce an RNA molecule that contains the information needed to specify a polypeptide with a specific amino acid sequence
regulatory gene
a gene that produces a repressor substance that inhibits an operator gene
repressor proteins
inhibit transcription by binding DNA sequences called silencers
activator proteins
specific transcription factors / bind to enhancer / as protein bends, activators bind to mediator proteins & general transcription factors to create active transcription initiation complex on promoter
lac operon
a gene system whose operator gene and three structural genes control lactose metabolism in E. coli
trp operon
a cluster of genes in a prokarytoic cell under the control of one promoter and one operator; the genes govern the synthesis of the necesary enzymes required to synthesize the amino acid tryptophan
corepressor
a small molecule that cooperates with a repressor protein to switch an operon off
repressible enzymes
An enzyme whose production is generally continuous but can be halted if a particular substance is present in concentrations greater than normal
regulatory proteins
a single protein that can set off a long series of events including the making of other proteins.
methylation
process that plays a role in the control of genetic expression, initiation of DNA Replication, Protection against Viral infection, and Repair of DNA
acetylation
the addition of groups to histones which unpacks chromatin and encourages transcription
siRNAs
first found in C. elegans(must know) it is complimentary to mRNA;inhibits gene expression by bind and inhibiting translation
recombinant DNA
genetically engineered DNA made by recombining fragments of DNA from different organisms
restriction enzymes
enzyme that cuts DNA at a specific sequence of nucleotides
sticky end
an end of DNA in which one strand of the double helix extends a few units beyond the other
vector
in biology, any agent, such as a plasmid or a virus, that can incorporate foreign DNA and transfer that DNA from one organism to another; an intermediate host that transfers a pathogen or a parasite to another organism
gel electrophoresis
procedure used to separate and analyze DNA fragments by placing a mixture of DNA fragments at one end of a porous gel and applying an electrical voltage to the gel
RFLPs
differences in homologous DNA sequences that are reflected in different lengths of restriction fragments produced when the DNA is cut up with restriction enzymes
DNA fingerprinting
a technique used especially for identification (as for forensic purposes) by extracting and identifying the base-pair pattern in an individual's DNA
STRs
Short Tandem Repeats, regions of a DNA molecule that contain short segments consisting of three to seven repeating base pairs, varies among individuals
cDNA
Complementary DNA. DNA produced synthetically by reverse trascribing mRNA. Because of eukaryotic mRNA splicing, cDNA contains no inrons.
PCR
polymerase chain reaction- DNA is copied multiple times to produce many copies of the original molecules helpful when there's only a small DNA sample