Genetics : Regulation of Gene Expression in Prokaryotes and Eukaryotes
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Example Question #193 : Genetics
Correctly order the 3 steps that initiate DNA transcription.
I. Catalysis of phosphodiester bond linkage
II. Polymerase binding to promoter sequence
III. DNA melting
II, III, I
III, II, I
III, I, II
I, II, III
II, III, I
The correct order of the processes that initiate transcription are as follows:
1. Polymerase binds to promoter sequence. At this point, the DNA is still bound together.
2. Polymerase melts DNA near transcription site. Hydrogen bonds are broken, opening the DNA.
3. Polymerase catalyzes phosphodiester bond linkage of initial 2 rNTPs (ribonucleotide triphosphates).
Example Question #194 : Genetics
Which of the following is a step performed by RNA polymerase during the elongation process of DNA transcription?
Melting DNA into an open conformation near the transcription site
Binding to the promoter region on the closed DNA complex
Advancement in the 3'-5' direction down the template strand
Catalysis of phosphodiester bond linkage at the initial 2 rNTPs (ribonucleotide triphosphates)
Advancement in the 3'-5' direction down the template strand
During elongation, RNA polymerase advances in the 3'-5' direction down the template, melting and adding rNTPs to growing RNA
Example Question #195 : Genetics
An autosome is __________.
a series of mutated genes
any chromosome that is not a sex chromosome
a sex chromosome
a gene pattern found only in vertebrates
any chromosome that is not a sex chromosome
By definition, an autosome is any chromosome that is not a sex chromosome. Humans have a diploid genome that consists of 22 pairs of autosomal chromosomes, and one special pair of chromosomes (which is nonautosomal) that determines gender (two X chromosomes = female, one X and one Y chromosome = male).
Example Question #196 : Genetics
The genetic code of an organism is determined by __________.
Ribosomal shapes
DNA sequence
Number of amino acids per protein
RNA sequence
DNA sequence
An important concept of genetics is that DNA contains the blueprint of all genetic information. It is the sequence of DNA that determines an organism's genetic code.
Example Question #11 : Regulation Of Gene Expression In Prokaryotes And Eukaryotes
The lac operon in E. coli bacteria is a widely used example of an inducible operon. In order for the operon to be expressed, __________ must be bound to the activator and __________ must be bound to the repressor.
cAMP . . . lactose
lactose . . . glucose
ATP . . . lactose
glucose . . . cAMP
lactose . . . cAMP
cAMP . . . lactose
The lac operon expresses enzymes used to break down lactose. It would be a pointless waste of energy to make those enzymes if there is no lactose present, or if there was glucose present — as glucose is a preferable source of energy to E. coli. High concentrations of cAMP signify low levels of glucose. cAMP binds to CAP, the activator of the lac operon, allowing CAP to bind to the promoter and then bind RNA polymerase to begin transcription. However, in the absence of lactose, there is also a repressor protein present that will block RNA polymerase from binding to the promoter. Lactose binds to the repressor and inactivates it, causing it to detach from the promoter and allow RNA polymerase to bind. Therefore, the expression of the lac operon is induced by the presence of cAMP and lactose.
Example Question #197 : Genetics
What differentiates mRNA from pre-mRNA?
All of the other answers are correct.
Presence of 5' guanosine cap
Presence of 3' poly-A tail
Absence of introns
Presence of exons
All of the other answers are correct.
All of the choices are correct. During processing of mRNA, the introns are removed and the exons are retained during splicing. A 5' guanosine cap and a 3' poly-A-tail is also inserted.
Example Question #201 : Genetics
What does the processing of mRNA ensure?
Removal of all uracil from mRNA transcript
Conversion from double stranded strand to single stranded strand
Simultaneous transcription and translation
Protection from degradation in cytosol
Translation of introns into a functional protein
Protection from degradation in cytosol
The purpose of mRNA processing is to protect it from degradation during its transport to cytosol. It does not involve introns or uracil. In addition, this concept has nothing to do with being double-stranded or single-stranded. Also, since the question states mRNA is being processed, it would imply that this takes place in a eukaryotic organism and hence, simultaneous transcription and translation is not possible.
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