(WIP) Ch 10 - Gene Expression, Transcription and Translation

Bio 190A

At the molecular level, ___ and ___ are key processes of ___ ___

transcription and translation; gene expression

Transcription

produces and RNA copy of a gene

Translation

interprets the nucleotide sequence in the messenger RNA (mRNA) to build a polypeptide with a specific amino acid sequence

Eukaryotes also use an

additional step of RNA modification

Central dogma

describes information flow from DNA to RNA to protein

Genes provide a “blueprint” for

the characteristics of organisms

Most genes are structural genes that code for

polypeptides

One or several polypeptides function as a ___ that plays some role in the cell

protein

DNA stores information; this information must be accessed at the

molecular level for genes to be expressed

Gene

an organized unit of nucleotide sequences that enables a segment of DNA to be transcribed into RNA and ultimately results in the formation of a functional product

The functional product is often a

protein, however it can also be an RNA molecule

A gene is composed of

specific base sequences organized in a way that allows the DNA to be transcribed into RNA

Important sequences include the

promoter, transcribed region, terminator, and regulatory sequences

Transcription occurs in 3 stages

initiation, elongation, termination

Initiation

a recognition step where the promoter functions as a recognition site

In bacteria, sigma factor binds to

RNA polymerase

Open complex

the complex between RNA polymerase and the separated DNA strands

Elongation

occurs as RNA polymerase synthesizes RNA

The DNA strand that is used as a template is called the ___ ___ and the opposite DNA strand is called the ___ ___

template strand; coding strand

The ___ is synthesized in the __ to __ direction

transcript; 5’ to 3’

Termincation

occurs when RNA polymerase reaches a terminator, releases the transcript, and dissociates from DNA

The basic features of transcription are ___ among all organisms

similar

Transcription of eukaryotic genes involves more

complexity of protein components

In eukaryotes, the product of transcription is a ___, and immature precursor that must be processed to form a ___ (functionally active) ___

pre-mRNA; mature mRNA

Pre-mRNAs undergo 3 ker modifications:

1. A 5’ cap is added

2. A 3’ poly A tail is added

3. During splicing, the introns (intervening regions) are removed, and the exons (expressed regions) are connected together

Capping occurs when

a modified guanine is covalently attached to the 5’ cap

The 5’ cap is recognized by __ ___ __ ___; it is needed for the…

a variety of proteins; mRNA ro exit teh nucleus and bind the ribosome

The poly A tail is added to

the 3’ end after transcription (via enzyme activity)

The poly A tail increases the

stability of the mRNA in the cytosol

Spliceosome <3

a complex that precisely removes introns

The spliceosome is composed of several different subunits known as

snRNPs, which contain small nuclear RNA and a set of proteins

Alternative splicing

allows complex eukaryotes to use the same gene to make different proteins

Splicing occurs in a series of steps, and the catalytic events of steps 3 and 4 are

catalyzed by an RNA component (ribosome activity)

Genetic code

specifies the relationship between the sequence of nucleotides in the mRNA and teh sequence of amino acids in a polypeptide