Bio 111 Purdue Recitation Quiz 4

The central dogma states that

DNA is transcribed by RNA polymerase into RNA then translated via ribsosomes to become proteins

The updated centra dogma suggests that viruses trick cells into transcribing and translating new viral proteins (ie: HIV) through reverse transcription, the flow is now…

RNA —-reverse transcriptase—→ DNA ——transcription——> RNA —-translation—→ protein

Reverse transcriptase is very error prone (T/F)?

T

________ Coding genes are transcribed into messanger RNA (mRNA) which then become protiens

Protein-coding

_____________ genes are transcribed into a specific kind of RNA which IS NOT translated into a protein (still very useful: tRNA, rRNA, microRNA)

non-protein coding

The promotor region is the site on the DNA sequence where _______ bonds

RNA polymerase

The coding region is the part with DNA sequnce that will be _________

translated

The orientation of the coding strand is ________

5’ to 3’

The orientation of the noncoding strand is ______

3’ to 5’

The coding strand contains the blueprint to make a protein and has the __________ sequence as the resulting mRNA

exact same (except coding DNA strand contains Thymine, mRNA contains Uracil)

The orientation of the mRNA strand is _______

5’ to 3’ (recall it is the exact same as coding strand aside from T and U nucleotides !)

RNA polymerase _______ the ______ strand of the gene

transcribes, template

Phases of transcripion

initiation, elongation, termination

What happens during the initiation phase of DNA transcription?

• _____________ attaches to the ____ region of the gene splitting the coding and template strands

RNA polymerase, promotor

What happens during the elongation phase of DNA transcription?

• _________ transcribes the ______ strand to generate the RNA transcript

RNA polymerase template

What happens during the termination phase of DNA transcription?

• RNA polymerase reaches the _________ sequence, it ____ from DNA and ______ the RNA transcript

termination, detaches, releases

Prokaryotes have ______ type(s) of RNA polymerase(s) involved in transcription

ONE

The prokaryotic RNA polymerase enzyme has 2 sections called what that together compose the holoenzyme.

Sigma Factor and Core enzyme

The function of the sigma factor is to ____

initiate transcription

The core enzyme is composed of ____(quantity/type) and _______(quantity/type) subunits that synthesize the RNA

2 alpha, 2 beta

The sigma factor (SF) ________ transcription in prokaryotes by binding to the promotor regions of genes and _______ the strands (similar to helicase)

initiates, separating

After transcription beings the sigma factors ______ from the core enzyme and subsequently ______ itself with another core enzyme to initiate the transcription of another gene. (aka: core enzyme completes transcirption without SF)

dissociate, associates

In prokaryotes transcription and translation are ______ because they __________________.

coupled, have no nucleus to separate genes and ribosomes. This means that mRNA is translated as soon as it is made.

Monocistronic mRNAs contain the ________ region of ____ gene(s).

coding, one

In prokaryotes many mRNAs are _____________.

polycistronic

Polycistronic mRNAs come from _________ called __________.

gene clusters, operons

Operons: contain sets of _______ that must be expressed _______

genes, simultaneously

The genes in an operon are transcribed ______ and _______ promotor and termination regions.

together, share

What would happen if there was only a single ribosome binding site in polycistronic mRNAs like Lac Operon?

Only the first coding region would be made.

Transcription in eukaryotes

• not coupled

• transcription occurs in _____

• translation occurs in _______

• utilizes 3 different _________ with different roles

• Have _____ instead of sigma factors

nucleus, cytoplasm, RNA polymerases, transcription factors

In DNA transcription in Eukaryotes RNA polymerase 1 ______________

transcribes rRNA

In DNA transcription in Eukaryotes RNA polymerase 2 ______________

transcribes protein coding mRNA genes

In DNA transcription in Eukaryotes RNA polymerase 3 ______________

transcribes tRNA and rRNA genes

In eukaryotes a new mRNA called pre-mRNA is modified in 3 ways

• two structures are added onto the end of each tail to protect against degradation

  • 7- methy- guanosine added to 5’ end mRNA via _________ linkage

  • addition of poly-A tail (~200 adenines) on 3’ end

  • mRNA is spliced by spliceosome

    • ______ are cut out of mRNA leaving _____ spliced together.

5’phosphate-5’phosphate

introns, exons

Splicosomes are made up of RNA and proteins : ___________ and ______

snRNAs: make up RNA component

snRNPs: ribonucleo proteins

The spliceosome binds the ____________ splice sites of intron an dsplices it out.

5’ to 3’

What happens to the intron after it is spliced out?

may be futher processed into noncoding RNA or degraded

Alternative splicing

when some exons are also spliced out

Alternative splicing allows _____k protein coding genes to produce _____k different proteins. improper function of alternative splicing is linked to diseases (cancer, autism, muscular dystrophy)

20, 100