Bio 250 - CH 7

Why do we regulate gene expression?

So you aren’t using energy and supplies you don’t need

Where does most regulation of genes occur?

Most regulation happens at the transcriptional level,

What are the categories of enzymes based on frequency of synthesis?

Constitutive, inducible and repressible

What are constitutive enzymes?

Continuously synthesize3d

What are inducible enzymes?

Only synthesized under specific conditions

What are repressible enzymes?

Routinely synthesized, but can be turned off

What is antigenic variation?

Random expression of one or several genes for a specific protien

What is an example of Antigenic variation?

The pili genes of Neisseria gonorrhoeae

What is phase variation?

Routine switching on and off of genes

What is an example of phase variation?

The phase variation of fimbrae within a population

What is the clinical significance of gene regulation in bacteria?

Help with natural selection- Antigenic variation and Phase variation

What is coupling transcription and translation?

Translation occurs while transcription is happening farther down the gene

Can coupling of transcription and translation occur in eukaryotes?

No

Why can’t coupling of transcription and translation occur in eukaryotes

Because they occur in different locations and Eukaryotes have to process RNA before Translation

What happens in Eukaryotic mRNA processing?

Need poly-A tail and cap, Pre-mRNA needs to be spliced and the ribosome is 80s

What is mRNA splicing and why does it occur?

Taking out the non-coding regions before translation so that the proteinWhat can be functional

What events occur after translation in prokaryotes?

Protein folding and protein modification

What is protein folding?

How the 3d shape of the protein is, chaperone proteins are involved in the process

What is protein modification?

Modify’s protein bases of of what the signal sequences say

What does Helicase Do?

Melts DNA- Splits H-bonds

What does DNA Gyrase do?

Relieves supercoiling

What is primase?

Synthesizes RNA primers

What is a primer?

Fragment of RNA nucleic acids where DNA polymerase can add nucleotides

What is DNA polymerase III?

Synthesize leading strand from 5’ to 3’ end stating at 3’

What is DNA polymerase I?

It removes RNA primer and replaces with with DNA

What does DNA ligase do?

Seals the nicks left over after the RNA primer is removed and replaced with DNA

What direction is DNA synthesized in?

5’ to 3’

What are okazaki fragments?

Newly synthesized DNA on the lagging strand - Its what is made in between the RNA primers as DNA Synthesis happens away from the replication fork.

Where are okazaki fragments found?

The lagging strand

What is the leading strand?

Synthesis happens towards the replication fork only 1 RNA primer is needed - starts synthesis

What is the lagging strand?

Synthesis happens away from replication fork between 2 RNA primers

What is the origin of replication?

Where DNA synthesis Begins and the DNA melts

What events happen in the origin of replication?

DNA is melted - H-bonds are broken and strands are separated

What is the function of RNA?

To convert genetic info stored in DNA into functional proteins - mRNA, tRNA, rRNA

What is a polysome?

Multiple ribosomes working on one gene

What is polysistzonic?

More than one coding region

Can polysomes and polysistzonic be in Eukaryotes?

No

What is the structure of DNA?

Anti-parallel strands, Double-stranded helix, 5’ to 3’

What is the structure of RNA?

Single-stranded, ribose, uracil

When is the only time a cell replicates?

When it is ready to divide

What does a cell do when it isn’t dividing?

Genes are expressed

Do all living organisms use DNA to store genetic info?

Yes

What is gene expression?

Converting info stored in DNA to a specific gene product

What is the oder for the central dogma?

DNA to RNA to protien

What is the structure of prokaryotic chromosomes?

Double stranded circle

What is the structure of Eukaryotic chromosomes?

double stranded helix

What is the template strand?

Serves as template for RNA synthesis

What is the non-template strand?

complementary to template strand but not used for transcription

What is the promotor?

Starting point for DNA where RNA polymerase binds to start transcription

What is RNA polymerase?

Catalyze transcription

What is the sigma factor?

recognizes the promotor only in prokaryotes

What is the terminator?

Ending point for transcription

What are the steps in translation initiation?

1. 30s ribosomes binds to the mRNA strand at binding site

2. F-met binds tRNA to codon (brings anticodon strand with it)

3. 50s ribosome binds

What are the steps in translation elongation?

1. Charged tRNA enters A site

2. A site and P site form a peptide bond because of peptidyl transferase

3. Translocation- ribosome moves 3’ 1 codon length

What is Transformation termination?

When release factors enter A-site and cause translation to disassemble (ribosomes release)

What is a codon?

Sequence of three nucleotides that code for an amino acid

What does it mean that DNA is a semi-conservative matter?

Each daughter cell has a copy of the original DNA

What are the products of Gene expression?

proteins and functional RNA

What processes are involved with gene expression?

Translation and transcription

What are the steps in transcription?

Initiation, elongation and termination

How does transcription Initiation work?

Holoenzyme binds promotor and melts DNA

How does Transcription Elongation work?

5’ to 3’ synthesis of complementary strand of RNA

What is re-anneling?

DNA strands come back together and reform H-bonds?

What is transcription termination?

When RNA polymerase reaches terminator, transcription stops

What is the function of the Anticodon?

Links amino acids together

What is rRNA?

Main component of ribosomes

What end of tRNA does the amino acid attach?

3’

What is the product of translation?

polypeptide chain

Are all RNA molecule produced during transcription translated into protiens?

No, only the ones that have mRNA