Exam 4 Flashcards
Discontinuous synthesis
Occurs on the lagging strand of DNA , in DNA replication, and consists of Okazaki fragments.
Complementary
In a DNA molecule, one side of the molecule is complementary, or base paired to the other side of the molecule.
Ie. A-T C-G
Semi-conservative replication
One parent molecule results in two daughter molecules.
DNA ligase
The enzyme which joins fragments of DNA together, such as Okazaki fragments, or restriction fragments.
Helicase
The enzyme which untwists the double helix, and separates the old strands so that DNA replication can occur.
Singe strand binding proteins
Proteins which bind to the unpaired strands of DNA in replication so that DNA polymerase can move down the strand and copy it.
Excision repair
Enzymes which cut out damaged segments of DNA, and randomly replaces it with nucleotides.
Transcription
Making a copy of DNA in the form of mRNA. The mRNA if formed by RNA polymerase.
Transcription unit
A gene or group of genes with a similar function, which are transcribed at the same time. It consisted of a start sequence, hundreds to thousands of nucleotides, and a stop sequence.
Triplet code?
A nearly universal code consisting of 3 nucleotides which code for a specific amino acid.
Translation
The process of making protein using mRNA, ribosomes, and tRNA.
Reading frame
The order in which the triplet code is read. Correct reading frame produces the correct protein. Incorrect reading frame produces incorrect proteins.
Transcription factors
Proteins which assist in getting RNA polymerase to bind and start transcription.
Promoter
A region of DNA, dozens of nucleotides upstream from the initiation site where transcription actually begins.
TATA box
A region rich in nitrogenous bases, 25 nucleotides upstream from the initiation site. RNA polymerase keys in on this site.
tRNA
A specialized form of RNA which has an anticodon on one end, to base pair with the codon of mRNA, and a specific amino acid attached to the top of it.
Wobble
A nonstrict base pairing of the third nucleotide of the codon and anticodon.
Ribosome
Composed of ribosomal RNA, and the actual site of protein production.
Aminoacyl-tRNA-synthethase
The enzyme used to attach the amino acid to the tRNA and uses ATP as an energy source.
DNA replication
The parent molecule opens into a replication fork, and new nucleotides are base paired into the fork, resulting into two, half old, half new daughter molecules.
Initiation factors
Special proteins that bring together mRNA, tRNA, and the ribosomal subunits.
Peptidyl transferase
This molecule is found in the ribosome, catalyzes the formation of peptide bonds between amino acids, and moves the growing peptide from the P site to the A site.
GTP
Provides the energy necessary for the initiation of translation.
Elongation factors
Proteins which help the process of translation.
Free ribosomes
All ribosomes start out as free ribosomes, and remain free if they produce proteins used in the cytoplasm of the cell. Ribosomes become bound to the ER if their product is going to be exported from the cell.
Signal sequence
A 20 amino acid sequence at the beginning of a peptide which allows the ribosome to attach to the ER.
5’ cap
A modified form of guanine, attached to the mRNA, which serves to protect it from hydrolytic enzymes.
Splicesomes
A large, complex enzyme which cuts and pastes mRNA, to form a mature mRNA.
Exon
A coding section of the mRNA which will result in a protein.
Intron
A sequence of mRNA which may code for ribosomes or other unknown functions.
Inducer protein
A protein which causes a structural change in the repressor, and allows transcription of the gene.
Repressor protein
A protein which causes a structural change in the repressor, and does not allow transcription of the gene.
Nonsense codon
A region of mRNA which causes early termination of the transcript.
Operator
A site of negative regulation. The repressor binds here, and blocks RNA polymerase.
Promoter
The RNA polymerase binds here.
Cap site
An activator protein binds here, upstream from the promoter, and unwinds the DNA molecule so that DNA polymerase can bind and read the gene. This is transcription.
Transformation
A change in bacterial gene, or genome due to the uptake of naked, foreign DNA from the environment, or in a test tube in an experiment.
Transduction
The transfer of bacterial genes from one host to another via a bacteriophage.
Conjugation
The direct transfer of DNA between two bacterium which are temporarily joined together by a sex pili.
Episome
A plasmid which can incorporate and remove itself from chromosomal DNA.
Genome
All of the DNA in an organism.
Transposon
Pieces of DNA which move from one area of the genome to another.
Conservation transposons
Genes that jump from one location to another without replicating before they jump.
Inverted repeats
Noncoding sequences of DNA 20-40 nucleotides in length, who’s ends are reciprocal mirror images of each other.
Transposase
A molecule which recognizes inverted repeats, cuts out the transposon, and regulates the remaining DNA.
Restriction enzymes
A molecule which recognizes a specific nucleotide sequence of DNA, and cut the DNA so that unequal, overlapping ends are formed.
Restriction fragments
A piece of DNA resulting from the use of a restriction enzyme.
Gel electrophoresis
Using a gel and electricity to separate DNA fragments by size.
cDNA
Complementary DNA
An artificial gene with no introns.
Genomic library
A set of thousands of clones or plasmids containing a gene, which represents the genome of an organism.
DNA fingerprint
A set of restriction fragments obtained from a human specimen.
Ie. blood specimen.
These fragments are unique to each individual.
