Transcription and RNA

The genetic information in genes must be ___

expressed

Gene expression occurs through two processes:

-___- converts DNA to RNA. Think about the root work ‘transcribe’, which is to copy the same language (i.e. language of nucleotides)

-__- converts RNA to protein. Think about the root word ‘translate’, which is to convert one language (i.e. nucleotides) into another (i.e. amino acids)

-Transcription

-Translation

___ is the process of converting DNA into RNA 

Transcription

RNA is chemically very similar to DNA with the following exceptions:

-Contains __ not deoxyribose

-Contains uracil (U) instead of thymine (T)

-Is typically ___

-ribose

-single-stranded

Transcription Produces RNA __ to DNA

Complementary

Transcription is similar to DNA replication

-A small region of double-stranded DNA is unzipped to expose __ strand (one of the two DNA strands)

-___ builds an RNA strand one nucleotide at a time (A, C, G, U) in the ___ direction, forming a phosphodiester backbone (just like with DNA)

-template

-RNA polymerase : 5’ to 3’

Transcription can be broken down into 3 steps:

- __: How, where, and when to start

-___: Continuation of transcribing DNA into RNA

-___: Stop of making RNA

-Initiation

-Elongation

-Termination

Termination: Stop of making RNA

-Eukaryotes: pre-RNA is __ modified into mRNA

-The pre-RNA often contains non-protein coding sections called __

-__ are regions that code for proteins. —- = Expressed in Protein

- post-transcriptionally

-introns

-Exons

-Note the __ strand (complementary to the RNA) that is used by the RNA polymerase

-The __ strand has a sequence equivalent to the RNA. I.e. 5’AGGTTC3’ in the DNA coding strand = 5’AGGUUC3’ in the RNA

-template

-coding

RNA that will be converted to amino acids (i.e. protein) is called __ RNA (mRNA)

messenger

Other types of RNA are not converted to amino acids, instead they can be regulatory, structural and enzymatic in nature:

-__RNA (___) - a major component of ribosomes (the protein factories)

-__RNA (__) - move amino acids to ribosomes

-__RNA (__) - regulate gene expression

-Ribosomal : rRNA

-Transfer : tRNA

-Micro : miRNA

A __ is a specific sequence within DNA that signals the start of a gene

promoter

With the help of __, bacterial RNA polymerase binds tightly to promoted regions and opens up the DNA helix to expose the template

sigma factors

Transcription ends when the polymerase encounters a ___ sequence (region that causes the polymerase to fall off)

terminator

1. The ___ TTGACA hexamer: found 35 nucleotides before transcriptional start (-35)

2. The ____ TATAAT hexamer is found at -18 to -9 nucleotides upstream from transcriptional start (-10)

1. -35 Element

2. -10 Element

Eukaryotic gene transcription differs from prokaryotic transcription in the following ways:

-___ types of RNA polymerases exist instead of one

-Eukaryotes require ___

-More elaborate control over transcription exists

-DNA packaging (e.g. ___) presents a challenge (no __ in prokaryotes)

-Three

-transcription factors

-nucleosomes : histones

RNA polymerase II requires the help of proteins called __

transcription factors

Transcription factor __ bind to a promoter region known as a TATA box (composed mainly of A and T nucleotides), which is typically ~ 25 nucleotides upstream from the start of a gene

TFIID

Together RNA polymerase II and these factors form the transcription __

initiation complex 

__ (in pink) phosphorylates the ‘tail’ of RNA polymerase II, which causes the cluster of transcription factors to fall of

TFIIH