Exam 2 Flashcards
Kinetochores
-fomred on the centromere region of the chromosome
-spindle microtubules attatch to the kinetochore
What is the differences between meiosis and mitosis?
-two daughter cells, each 2n are produced in mitosis
-four daughter cells, each n are produced in meiosis
-Meiosis has two different separations stages while mitosis only has one
What is the relationship between being haploid and meiosis?
-Haploid: n, has only 1 copy of the chromosome
When do the cells in meiosis become haploid?
after meiosis II
What is the relationship between diploid and mitosis?
Diploid: 2n in mitosis for a total of 46 chromosomes; this is when the cell has two sets of chromosmes
Sugoshin
protein that prevents cohesin degradation during meiosis I
What does sugoshin help protect?
cohesin at the centromere
-it is eventually degraded and allows the cohesin at the centromeres to break down and allows the chromosomes to seperate
Template Strand in Transcription
the strand that is transcribed
-contains the transcription unit: a promoter, RNA coding sequence, terminator
Non-Template Strand in Transcription
not usually transcribed
What is the function of the sigma factor?
binding to the promoter when transcription starts
What is created when the sigma factor binds to the core enzyme and what is the function?
-holoenzyme
-capable of binging promoter and initiating transcription as it is one of many transcription factors
Eukaryotic promoters
-direct RNA polymerase to know where to go (not transcribed)
-normally negative and upstream
Prokaryotic Promoters
-consensus sequences are used as promoters
- -10 consensus: 10 bp upstream of the start site
- -35 consensus sequence: TTGACA
-Location of sequence determines start site of transcription
What has been shown experientally to influence transcription?
Base mutations in promoters
What binds to the promoter in prokaryotic transcription?
holoenzyme
How does termination occur in rho-dependent termination?
uses a terminator sequence to cause polymerase to pause
-Rho protein binds to the rut site and moves toward the 3’ end
-When RNA polymerase encounters a terminator sequence it pauses and allows rho to catch up and unwind the DNA-RNA hybrid stopping transcription
How does termination occur in rho-independent transcription?
hairpin structure, followed by a string of uracils
-transcription terminates when inverted repeats form a hairpin followed by a string of U’s because it destabilizes DNA-RNA pairing
How are -10 and -35 useful to promoters?
both are consensus sequences and are found upstream of the start site
-sigma factor binds to core enzyme creating a holoenzyme. This then binds to the -10 and -35 sequence
Basal Transcription Apparatus is found where and what is its function?
-general transcription factor and RNA polymerase
-these are only found in eukaryotes and bind to the promoter to recruit RNA polymerase
What is the role of the 5’ and 3’ UTR?
-help initiate translation
-5’ end is bound by proteins that are recognized by the 5’ cap and 3’ tail
-have clear distinction where coding stops and UTR starts which sets the reading frame
What is an intron?
-intervening sequences that are removed by DNA splicing
-rare in prokaroytes; all classes of eukaryotic genes contain introns
-variable length; 200 to over 50,000 bp
What is an exon?
expressed coding region
What is the splice some?
removes introns and rejoins exons
Where does the splicesome remove introns at?
-5’ consensus sequence: GU A/G AGU (where splicing occurs on 5’ end)
-3’ consensus sequence: CAGG
What is the branch point in the splicesome mechanisim?
the adnenine that is ~18-40 NT’s upstream of 3’ splicing site
What can happen if the branch point is deleted or mutated?
splicing is prevented
What is the splicesome made out of?
five RNA molecules + 300 proteins which controls the process of splicing
What does splicing require?
consensus sequense that are present at the 5’ splice site and the 3’ splice site, with a weak one at the branch point
How many steps is splicing? What is it facilitated by?
-5 snRNAs
-2 step process
siRNA function
triggers degradation of other RNA molecules in eukaroytic cells in the nucleus and cytoplasm
miRNA function
inhibits translation of mRNA in eukaryotic cells in the nucleus and cytoplasm
E site function
exit site
P site function
peptidyl site occupies fMET-tRNA
A site function
aminoacyl site; EF-Tu, GTP, and charged tRNA form a complex
