Molecular Biology

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Transformation

Back 1

change in a phenotype and genotype due to the assimilation of outside DNA

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bacteriophages

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bacteria eaters

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virus

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DNA or RNA enclosed by protective coat

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Chargaff's rules

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1) base composition varies between species
2) within a species, number of A and T equal, C and G equal

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antiparallel

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subunits run in opposite directions

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DNA polymerase

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catalyze synthesis of new DNA by adding nucleotides to a pre-existing chain

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leading strand

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DNA pol III remains in replication fork on template strand and continuously adds nucleotides to new DNA strand as fork progresses

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lagging strand

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DNA strand elongating away from the replication fork, synthesized discontinuously

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Okazaki fragments

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series of segments in lagging strand

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mismatch repair

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other enzymes remove and replace incorrectly paired nucleotides that result from replication errors

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nucelase

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segment of strand containing damage out by DNA cutting enzyme

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telomeres

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don't contain genes, consists of repetition of short nucleotide sequence, buffer protects organisms genes

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telomerase

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catalyzes lengthening of telomeres in eukaryotic

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gene expression

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DNA directs the synthesis of proteins (sometimes just RNA)

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transcription

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synthesis of RNA using information in the DNA, "rewritten" from DNA to RNA

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messenger RNA (mRNA)

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carries genetic messages from the DNA to the protein synthesizing machinery of the cell

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translation

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synthesis of a polypeptide using the information in the mRNA, takes place in cytoplasm

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primary transcript

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initial RNA transcript from any gene

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triplet code

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genetic instructions for a polypeptide chain, written in DNA se series of non overlapping 3 nucleotide words

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template strand

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only one of two DNA strands transcribed, provides pattern for the sequence of nucleotides in an RNA transcript

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codons

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mRNA nucleotide triplets written 5' to 3' direction

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reading frame

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read symbols in correct groupings

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RNA polymerase

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enzyme pries two strands of DNA apart and joins together RNA nucleotides along DNA template strand

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promoter

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sequence that RNA polymerase attaches and initiates transcription

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terminator

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signals at the end of transcription

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transcription unit

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stretch of DNA that is translated into RNA molecule

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start point

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nucleotide where RNA actually begins

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transcription factors

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collection of proteins that mediate the binding of RNA polymerase and initiation of transcription

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RNA processing

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both ends of primary transcript are altered, certain interior sections of RNA molecule cut out

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5' cap

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modified form of guanine added to 5' end after transcription

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Poly A tail

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at 3' end enzyme adds 50-250 more adenine nucleotides

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RNA splicing

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removal of large portions of RNA molecule initially synthesized, cut and paste job

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introns

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noncoding segments of nucleic acids that lie between coding regions

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exons

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eventually expressed, usually translated into amino acid sequence

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splicesome

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interacts with certain sites along intron, releasing intron which is rapidly degraded, joining together the two exons that flanked the intron

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ribozymes

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RNA molecules that function as enzymes