Friday, July 4, 2008

LAC OPERON

Please post all your questions and comments regarding prokaryotic gene regulation (including lac operon stuff!) here.

Have a look at the 'page with questions and answers' (see link on the side) and at the link relative to prokaryotic gene regulation....I am posting practice questions and bits and pieces of notes there. Dr Beatty's notes (on  the course website) are also great.

Have a good weekend!

PS: Thanks for your questions! The answers are a little more involved that you may expect, so I posted them here (under 'students' questions and answers). have a look and let me know if they help.

12 comments:

Anonymous said...

Hi Pam,
I have a question regarding mutations in operator. http://www.mun.ca/biochem/courses/4103/topics/lac_genetics.html
If u look at the figures in the table under the mutations in operator, u actually notice that the combined figure for merozygote/
merodiploid is higher than the individual haploid operon systems. Do we have to take take this into account in determining the
extent of expression (ie ++, + ,-) for the purpose of this course. Next, i am confused with the Oc , does it mean that we
just consider it as inducer being present and in the absence of glucose, it will give the maximum expression (or fully induced).
What does constitutive expression really means ? Does it mean transcription all the time ? What distingushes between constitutive
and basal level transcription? What is Craig's definition on constitutive transcription ?

Thanks
Kean Wei

Anonymous said...

It is http://www.mun.ca/biochem/courses/4103/topics/lac_genetics.html

Anonymous said...

Thanks for the link and for the questions.

I addressed your questions and posted the answers here:

http://www.cfkeep.org/html/snapshot.php?id=2884582730834

Anonymous said...

Hi Pam,
What is the difference between a heterodiploid and merodiploid?

Thanks
Kean Wei

Anonymous said...

Heterodiploid will be heterozygous, while a merodiploid is diploid for a part of its genome, but not necessarily heterozygous.

Anonymous said...

Hi Pam,
thanks for your help!
I am just wondering about ONPG which is a reporter (indicator) for B galactosidase. However it is quantitative assay. So does that mean that the extent of LacZ expression can be differentiated between merodipliod and haploid lac operon systems using ONPG?

Thanks again
Kean Wei

Anonymous said...

Oops it should be merodiploid!

Anonymous said...

yes, you can use ONPG for that.

Anonymous said...

Hi Pam,
there seems to be a mistake in the first question of Restriction mapping.
Under the heading Plasmid alone,
shouldn't it be
PstI NotI : 1 band @ 0.2kb, 1 band @ 1.8kb
PstI EcoRI : 1 band @ 0.1kb, 1 band @ 1.9 kb
instead of
PstI NotI : 1 band @ 0.2kb, 1 band @ 2.8kb
PstI EcoRI : 1 band @ 0.1kb, 1 band @ 2.9 kb

Thanks.

Anonymous said...

It's all fixed up.
Thanks for pointing out the mistake!

Anonymous said...

Hi Pam,
referring to the above question, how come there is no 0.2 band when a double digest is done with Pst1 and Not1 from the prep plasmid #12.
Is the plasmid vector alone used to make prep # 12 recombinant plasmid?

Thanks.

Anonymous said...

hi,pam
can you post the answer for the winterrose question?thank you