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Bio Exam 3 Flashcards (Lecture 24)
Terms in this set (24)
What is the central dogma of biology?
the main purpose of genetic material is to encode the production of proteins in the correct cell , at the proper time, and in suitable amounts
a segment of DNA composed of specific base sequences organized in a way that allows the DNA to be transcribed into RNA and ultimately results in the formation of a functional protein product
transfer RNA (tRNA)-
needed to make polypeptides during translation
Ribosomal RNA (rRNA)-
forms parts of ribosomes which provide the site where translation occurs
signals the beginning of transcription
site for the binding of regulatory proteins; regulatory proteins are used to influence the rate of transcription
this region contains the information that specifies an amino acid sequence
signals the end of transcription
protein in bacteria that binds to both RNA polymerase and the DNA promoter
DNA strands form this; determines when the initiation step is complete
What are the stages of RNA replication?
1.) initiation-the promoter functions as a recognition site for sigma factor. RNA polymerase is bound to sigma factor which causes it to bind to the promoter. Following binding, the DNA is unwound to form an open complex.
2.) elongation/synthesis of the RNA transcript-sigma factor is released , and RNA polymerase slides along the DNA in an open complex to synthesize RNA
3.) termination-when RNA polymerase reaches the terminator, it and the RNA transcript dissociate from the DNA
How does RNA splicing work?
Introns are removed from the pre-mRNA by the spliceosome, a complex composed of snRRPs.
step 1: spliceosome subunits bind to 3 specific sequences in the RNA
step 2: intron looped outward, exons brought close together
step 3: 5' splice site cut and attached to branch site
step 4: 3' splice site cut and exons are attached together; intron loop released and degraded
What does alternative splicing allow?
It allows a single gene to produce multiple mRNA and protein variants
What do the 5' cap and 3' tail do?
they aid in export from nucleus and prevent degradation in cytosol
tells us how the sequence of nucleotides codes for the sequence of amino acids
three base pair groups that specify an amino acid; 64 possible codons, but only 20 possible amino acids
site for binding of ribosomes
a codon that specifies the first amino acid in a polypeptide sequence
a series of codons from the start codon to the stop codon that determine the sequence of amino acids of a polypeptide
specifies the end of translation
transfer RNA's (tRNA)-
bring the correct amino acid encoded by the mRNA codon
a part of tRNA that is complementary to a codon in the mRNA, which corresponds to an amino acid that the tRNA carries
What protein binds to one DNA strand to separate DNA strands and keep the replication fork moving forward?
Why is DNA topoisomerase necessary?
To keep the unopened helix from coiling tightly in the wrong direction
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