Flashcards in CH16 final Deck (25):
define origins of DNA replication
The replication of a chr begins at particular sites ...
short stretches of DNA having specific sequence of nucleotides
Define replication fork
At each end of replication bubble
are enzymes tht untwist the dbl helix at the replication fork. separating the 2 parental strands and making them available as template strands.
define okazaki fragments
the lagging strand is synthesized discontinuously, as a series of segments . these segments of the lagging strand are called okazaki fragments
Define DNA polymerase
these enzymes catalyze the synthesis of new DNA by adding nucelotides to preexisting chains
define DNA ligase
joins the sugar phosphate backbones of all the okazaki fragments into a continuous DNA strand
Define leading strand
DNA polymerase III . this continuously adds nucleotides to the new complementary strand as a fork progresses . the DNA stand made by this is called the leading strand 5' ---> 3' end tht is being made
Define lagging strand
Is adding nucleotides towards the 5' end.
this means primase primers the a 5' end and DNA polymerase III synthesizes the okazaki fragment until it hits the next primer.
DNA polymerase I removes the primer and replaces it w/ nucleotides but the chain is not attached until DNA ligase connects the strand of nucleotides together
other enzymes remove and replace incorrectly paired nucleotides tht have resulted from replication errors.
An area where there are damaged DNA it is cut out by nuclease and is filled in w/. new nucleotides
describe how DNA becomes transcibed and translated into proteins tht run metabolism
Transcription- is the synthesis of RNA using info from DNA .
translation - is the synthesis of a polypeptide using info in the mRNA .
carries a genetic message from the DNA to the protein synthesizing machinery
Genetic instructions for a polypeptide chain are written in the DNA as a series of nonoverlapping 3 nucelotide words
the mRNA nucleotides triplets are called codons
Reading the sequence of nucleotides triplets correctly
The DNA sequence where RNA polmerase attaches and initiates
The stretch of DNA downstream from the promoter tht is transcribed into an rna molecule
In ek a collection of proteins called """" mediate the binding of RNA polymerase and the initiation of transcription
Pries the 2 straands of DNA apart and joins together RNA nucleotides complementary to the DNA template strand
Poly A tail
is attached to the 3' end
The noncoding segmetnts of nucleic acids tht lie between coding regions
The are expressed usually by being translated into amino acid sequences
RNA molecules tht function as enzymes
the message is a series of codons along an mRNA molecule and the reanslator is called tRNA