Chapter 15,16,17 Lecture 17 Flashcards
What disease are the Hutterites effected by>
Bowen-Conradi Syndrome
- results from defective ribosome biosynthesis affecting the process of translation
- Emg1 is essential for 40S ribosome subunit biogenesis
one gene, one enzyme hypothesis
-Beadle and Tatum 1941
0 genes function by encoding enzymes, andeach gene encodes a separate enzyme
auxotrophic mutation 103 grows on minimal medium supplemented with A, B, or C. Mutation 106 grows on medium supplemented with A and C, but not B; and mutation 102 grows only on medium supplemented with C. what is the order of A, B, C, in a biochemical pathway?
B –> A –> C
structure and function of proteins
- proteins are polymers consisting of amino acids linked by peptide bonds
amino acid sequence is its primary structure - this structure folds to create secondary and tertiary structures
- 2 or more polypeptide shians associate to form quaternary structure
What primarily determines the secondary and tertiary structure?
the primary structure
a codon is
a. one of three nucleotides that encode an amino acid
b. three nucleotides that encode an amino acid
c. three amino acids that encode a nucleotide
d. one of four bases in DNA
b. three nucleotides that encode an amino acid
degenerate code
amino acid may be specified by more than one codon
synonymous codons
codons that specify the same amino acid
isoaccepting tRNAs
different tRNAs that accept the same amino acid but have different anticodons
sense codons
encoding amino acids
initiation codon
AUG methionine
termination codon
UAA, UAG, UGA
- stop codons
through wobble, a single ___ can pair with more than one ___
a. codon; anticodon
b. group of three nucleotides in DNA: codon in mRNA
c. tRNA; amino acid
d. anticodon; codon
d. anticodon; codon
reading frame
3 ways in which the sequence can be read in groups of three;
-each different way of reading encodes a different amino acid sequence
nonoverlapping
a single nucleotide may not be included in more than one codon
universality of the codon
near universal, with some exceptions
Do the initiation and termination codons specify an amino acid? if so which one?
initiation does
- bacteria = n-formylmethionine
eukaroytes = methionine
amino acids bind to which part of the tRNA?
a. anticodon
b. DHU arm
c. 3’ end
d. 5’ end
c. 3’ end
during the initiation of translation, the small ribosome binds to which consensus sequence in bacteria?
the Shine-Dalgarno sequence
What sequence facilitates the identification of the start codon?
the Kozak sequence
The initiation of translation requires what?
initiation factors
- IF-3
- initiator tRNA with N-formylmethionine attached to form fmet-tRNA
- GTP (energy molecule)
in elongation, the creation of peptide bonds between amino acids is catalyzed by
a. rRNA
b. protein in the small subunit
c. protein in the large subunit
d. tRNA
a. rRNA
polyribosomes
an mRNA with several ribosomes attached
in a polyribosome, the polypeptides associated with which ribosomes will be the longest?
a. those at the 5’ end of mRNA
b. those at the 3’ end of mRNA
c. those in the middle of mRNA
d. all polypeptides will be the same length
b. those at the 3’ end of mRNA
What are some of different processes that affect gene regulation by altering chromatin structure?
modification of histone processes (methylation and acetylation)
and DNA methylation
most transcriptional activator proteins affect transcription by interacting with
a. introns
b. basal transcription apparatus
c. DNA polymerase
d. the terminator
b. basal transcription apparatus
How does the binding of regulatory proteins to enhancers affect transcription at genes that are thousands of base pairs away?
the DNA between the enhancer and the promotor loops out, so regulatory proteins bound to the enhancer are able to interact directly with the transcription apparatus
How does the poly(A) tail affect stability?
the poly(A) tail stabilizes the 5’ cap which must be removed before the mRNA molecule can be degraded from the 5’ end
in RNA silencing, siRNAs and miRNAs usually bind to which part of the mRNA molecules that they control?
a. 5’ UTR
b. segment that encodes amino acids
c. 3’ poly (A) tail
d. 3’ UTR
d. 3’UTR
What is a constitutive gene?
a constitutive gene is not regulated and is expressed continually
why is transcription a particularly important level of gene regulation in both bacteria and eukaryotes?
because it is the first step in the process of information transfer from DNA to protein . for cellular efficiency, gene expression is often regulated early in the process of protein rpoduction
how do amino acids in DNA-binding proteins interact with DNA?
a. by forming covalent bonds with DNA bases
b. by forming hydrogen bonds with DNA bases
c. by forming covalent bonds with DNA sugars
b. by forming hydrogen bonds with DNA bases
What is the difference between a structural gene and a regulator gene?
a. structural genes are transcribed into mRNA, but regulator genes aren’t
b. structural genes have complex structures; regulator genes have simple structures
c. structural genes encode proteins that function in the structure of the cell; regulator genes carry out metabolic reactions
d. structural genes encode proteins; regulator genes control the transcription of structural genes
d. structural genes encode proteins; regulator genes control the transcription of structural genes
in a negative repressible operon, the regulator protein is synthesized as a. an active activator b. an inactive activator c. an active repressor d, an inactive repressor
d, an inactive repressor
in the presence of allolactose, the lac repressor a, binds to the operator b. binds to the promoter c, cannot bind to the operator d. binds to the regulator gene
c, cannot bind to the operator
in the trp operon, what happens to the trp repressor in the absences of tryptophan?
a, it binds to the operator and presses transcription
b. it cannot bind to the operator and transcription takes place
c. it binds to the regulator gene and represses transcription
d. it cannot bind to the regulator gene and transcription takes place
b. it cannot bind to the operator and transcription takes place
attenuation results when which regions of the 5' UTR pair? A. 1 and 3 b. 2 and 3 c, 2 and 4 d. 3 and 4
d. 3 and 4
What is the effect of high levels of glucose on the lac operon?
a. transcription is stimulated
b. little transcription take place
c transcription is not affected
d. transcription may be stimulated or inhibited, depending on the levels of lactose
b. little transcription take place
