Mug Mug Mug

Mug Mug Mug
I am sure you are in the heat of things now.

I did not manage to catch/see a few of you for the past one and a half week esp some of the 3S's but I understand that you may be trying to clear that huge pile of bio readings and not ready to see me...so I can only wish you the best.

Good Luck to all yah!

Why repressible operon- anabolic and inducible - catabolic

A question ask by Phil but my edumail is down so I couldnt get to reply via that channel. A good question nonetheless.

A repressible operon is such so that the end-product of an anabolic pathway can regulate the pathway as negative feedback - no wastage of resources; no need to produce more product.

A inducible pathway is also to prevent wastage of resources because it will only be 'on' if the conditions are right e.g. in the case of the lac operon, if there is a ready source of glucose, why waste energy to hydrolyse lactose?

Format of Paper

Knock knock.
Pls check your 'Revision Promotional Examination 2006'for the format yah?
Although it could be lying somewhere in that stack of chemistry notes.

Provirus? Is it actively transcribed?

Nope.

A provirus is not active while integrated into a host genome in this way. Instead, it is passively replicated along with the host genome and passed on to the original cell's offspring; all descendants of the infected cell will also bear proviruses in their genomes. Eventually, in response to changes in the host's environmental conditions or health, the provirus will be activated and will serves as a template for massive transcription of its viral genome.

http://en.wikipedia.org/wiki/Provirus

What happens to T4 Empty Capsid after Injection ?

What happens to the empty capsid after the phage genome has been injected into the bacteria?

It usually remains on the cell surface until environment favors its dissociation
(activation energy necessary for dissociation of capsids is very high)

Neo-Darwinism versus Darwinism

What is Neo-Darwinism about?

When Darwin proposed his theory, he did not account for 'why are there variations in a population?'. His theory was based on observations that he made and with the underlying clause that there is always variation in a population.

In Neo-Darwinism, with the knowledge of molecular biology, Darwin's theory was expanded to account for 'why are there variation in a population' for a complete picture which we have already done so in tutorials:
1) heritable differences: meiosis (crossing over + independent assortment) + random fusion of gametes
2) mutations (gene and chromosomal)

Amendment to Sensei-tional test

Pls note below.

Today I realised that many still have not caught on to this site yet.
I understand 'cos I barely check online forum while in school too in the past, well-intended things might be.

Do let your classmates know if anything rises and that some answers can be found on this site via your class email.

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As kindly pointed out by Jordan,
In Bio Essence: DNA genomics Exercise:

The answer to 2(c), For Transcription: it should be RNA polymerase instead.
DNA polymerase is used in replication not transcription.

I will make all the above corrections and update the already uploaded files by 7pm.
Thanks!

Consultation Slots

Ok I am worried about some of you but I also know that some of you have reserved these few days to bury yourself in the tons of information. FYI:

Fri:
12 pm - Azura
2 pm - Shu Zhang
4 pm - Amanda

Sat:
2pm - Zhang Rui
3:30pm - Weiquan n Poh

If you would like to see me, drop me a note or check with the above students if you can join in at the prescribed slots.
I can stick around for a whlie so dun paiseh about timing - just check with me

Conceptual Answers to Ur Questions

This post was with reference to some questions posed by some students:

How does inbreeding result in a loss of genetic variation?
> i know that there is a collection of recessive alleles
> but isn't there crossing over to create variation?

Variation comes in all form. You are right to sasy that crossing over of non-sister chromatids of homologous chromosomes ensures variation but it is more significant at the individual level. Comparatively, there is a loss in the genetic variation because of the crossing over is done within a particular gene pool. No matter how you cross within a population, you are going to get only that few alleles (nelgecting mutation) for a gene. If you have cross/inter-breeding, you are open to more alleles and thus there is increased in genetic variation because the gene pool has expanded in quality.

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How genetic uniformity would hamper the abiliy of species to adapt to ecological changes? (4)

> i know that there is little variation for natural
> selection to work on, but will it be extremely harmful or curb
> their chances of survival?

Yes because we are talking about the ability to survive into the next generation. So a change in environment can render the destruction of every individual in the population if there is no variation to increase the chances of survival for the species in the form of selected few who can continue the propagation of the species.

Thus I think as a guide you could have:
- genetic uniformity - no variation in population e.g. asexual reproduction which is conducive in a constant/stable environment
- But ecological changes e.g. environment/climate/predation can result in the destruction of every individual of a population if no variation exists.
- Because variation in a population will ensure that ..........
- thus the surviving few can reproduce and .........

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To add to the post on Neutral Theory, do you know that when we talk about molecular homology we are examining the molecular homology of a particular amino acid sequeneces that give rise to a particular (conserved) protein e.g. mitochondria?

Consultation

Please be informed that I have invilgilation duties on Thurs (8-11) n Fri (8-12).
Will only be able to see you after duty.

Am already taken up on Thurs 11-12:30 WQ
Fri: to be confirmed. ZR and Az can drop me a mail?

Bio SenSei-tional Test 2006 (Answers)

Pls note that there is an amendment to answer on HIV versus lambda phage comparison:
HIV enter the cell by "direct fusion of membrane" not endocytosis.
FLu influenza virus enter by endocytosis.
I thot i have made the amendment but apparently not when I checked just now.


Took some time to tweak so here it is

Bio Essence: DNA Genomics

Finally as promised for Bio Essence: DNA genomics

Calcium chloride in Transformation

The exact reason/mechanism involved in the use of CaCl2 too increase cell permeability is not well-known. Its function was determined through empirical means / trial and error. =)

Making Sense of the Neutral Theory

Neutral Theory noted that at the molecular level, evolutionary changes that occured are selectively neutral and is driven by genetic drift rather than by natural selection. (you already know this)

Because of selective neutrality in mutations (no effect on fitness), polymorphism is found within a population and all of its individuals can reproduce to pass on their different alleles. With that, the only determinant for the propagation of a particular allele will be genetic drift - chances that a particular allele will be passed on, which increases in a smaller population.



The theory sets the basis for the Molecular Clock:
Kimura, King and Jukes made the assumption that most aa substitution

- occur at a constant rate and
- are selectively neutral
(=the substitution is not lethal and does not affect the fitness of the organism)

Since the fitness of organism is not affected despite the mutation, we can thus track the changes in aa sequences over a long period and we can also observe polymorphism within a population.

And since the substition occurs at a constant rate, by observing the aa sequences diferences of particular proteins or genes for two species, we can deduce their evolutionary history i.e their approximate period of divergence from a common ancestor.

If a particular gene is important in function, variation in the resultant aa sequences will not be observed frequently

How enveloped viruses enter cells

Made a booboo yesterday.

There are two ways by which enveloped virus enter cells.

For the flu influenza virus, it does so via endocytosis. Indeed, the nucleocapsid is enclosed in two layers of membranes but the membranes will then fuse to release the nucleocapsid into the cytoplasm where the capsid will be digested away (uncoated) and reveal the nuclei acid.

For HIV virus, there is direct fusion of viral membrane with the cell membrane such that the nucleocapsid enter the cell directly and will be digested ......blah.

Mutation of LacZ gene and Allolactose

Mutation of LacZ gene can result in a non-functional beta-galactosidase.
Beta-galactosidase can engage in two pathways. One to lyse lactose to glucose and galactose and the other to convert lactose to allolactose. Allolactose is indeed an isomer of lactose but its presence needs the working of beta-galactosidase aka does not occur naturally.
Thus with a mutated beta-galacosidase, no allolactose can be formed. repressor proteins cannot be removed from operator. No structural genes in lac operon will be transcribed.

FYI: Permease is a membrane bound protein that facilitate the movement of lactose into the bacteria. If the LacY gene is mutated and a non-functional permease is expressed, no lactose will enter the cell and thus no allolactose can be formed as well.

Distal trpR regulatory gene

Someone goes:
Why is the trpR regulatory gene distal while lac operon's LacI gene proximal to the promoter? What is the purpose? Isn't it better to have the regulatory gene close to the operator for quick access and a better response to environmental changes?

Yea. However in the case of the trp repressor, the protein has been found to be capable of binding to at least 5 other operators in other operons as well. Thus its distal nature in trp operon could have been a compromise.

Cheers

Epistasis versus Linked Genes

Epistasis

Epistasis is used to describe the situation where one gene can mask the phenotypic effects of a different gene.
Typically, the two genes are involves in an enzymatic pathway that affects ONE phenotype.


CASE: When Bateson and Punnett crosses two different varieties of white-flowered plants, all their F1 generation plants had purple flowers!!!

Colorless precursor ---EnzymeC--> Colourless intermediate ---EnzymeP---> Purple pigment

Imagine the crossing: CCPP x ccPP --> CcPp (both genes have a dominant allele; enzyme C and P are functional)

However for the F2 generation you get a ratio of 9 purple :7 white !

If you work out the punnett square for CcPp x CcPp, would you be able to determine which gametic combination will give rise to the white phenotype?


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For linked genes, we are usually refering to two different phenotypes that will be expressed still

Wobble Hypothesis

61 possible codons - 20 amino acids - all due to the degeneracy of code as given in the wobble hypothesis.

Under the Wobble Hypothesis, the third position in a codon can tolerate some mismatch. Thus a single type of tRNA can recognize more than one codon.
Example: a tRNA with anticodon sequence of 3'-AAG-5' can recognize a 5'-UUC-3' and a 5'-UUU-3' codon even though only the former is perfect match according to the AU/GC rule.

The ability of a single tRNA to recognise more than one codon makes it unnecessary for the cell to make 61 different tRNA molecules for 61 different codons.

It probably also provide some leeway for mutations? =)

Evolution Crossword

Here is the answer key to the crossword on evolution.
I think I only managed to show it to one class due to the disruption of schedule from SPA.

Cheers

Celebrating Life

Yesterday we mourned the demise of a friend, an acquaintance or a school mate.
Some students were affected while others carried on with their lives. Really, losses never strike us until they strike close.
With about a decade between the students and I, a handful of friends have already left me behind. Maybe it is age but there is perhaps, a better acceptance of such unfortunate incidents. Although the initial ain of loss will never be eradicated, it was at least buffered.

But I would never forget CF.
About a decade back, she disappeared from my/our lives, alledgedly murdered. It did not help that I actually saw her a week before her demise at a school performance. I had wanted to go up to her then and just say a word of 'hi'. But in the end, I decided not to when I saw her preoccupation with her clique and the crowd that separated us.
i didn't get to say hi and that thought lingered.

In my drawer lies the huge golden clip she gave to me when my folder was in a mess with paper astrewn. And with that, came the reminder that besides thinking of a loss, we should not forget about celebrating the living when emotions are tamed. Life moves on, just like the rising and setting of the sun. I am always glad for the family and friends around me and I am not afraid to express so to them because we are only alive in each instance. I have a peculiar dream a few years back and if it holds true perhaps, I would not be hanging around for too long. So, everyday I am happy because I see people I appreciate and care for everywhere - until I get upset by them - yet that only lasts so long. So try not to forget that 'hi' or smile as we celebrates life with people around us. As for CF, I willl always be glad that our paths have crossed and those memories that we shared.

Someone told me that I could have been more sensitive during lecture on Thurs.
But surely, someone who is upset may not choose to express it on his/her face and some of us have to remain strong for others.

Day 4

Day 2

It needs a bigger container i think.
The blue mark indicates its size yesterday

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Students laughed with me/at at the following things:
1) for no reason
2) for my weird pronunication
3) for my advanced* technolgical ability

I have a bit of hearing problem if no one noticed. I could not catch nuances of English words easily for as long as I remember, much handicapped in the auditory department. Thus my body compensate this deficiency with a stronger visual department, so sometimes when I speak, I see images or words...until I lost it and need to concentrate like tuning a fizzy television into clear screen.
But then it is alright. Do correct me when I need to revise my pronunication because sometimes my brain might process words in funny configurations. Thanks. Although I am sure someone did say pro-Kar-yotes to me before. =P

Tech stuff. We are all learning. Bleah.

Virus and Bacteria Tutorial

Before i forget which happens often whenever I go to classes for reasons unknown, here are the stuff which I would not be going through. They are meant for your own understanding and checking.

How Plasmid/Virus Integrate Into The Bacterial Genome + Recombination

Generalised Transduction

Snustad. Simmons. Jenkins: principles of genetics (575.1 SNU)
The above book covers bacteria and virus pretty well although it may be a bit extensive. For those who wants to know more, you can seek out this book in the library =)

To answer a question that was posed this morning Wed 12/9 (notes is not wrong but probably unclear).

Transduction:

1) Generalised - the phage can transfer any segment of the bacterium genome to another bacterium.
2) Specialised – only restricted segments of the bacterial genome is transferred (those close to the integration site)


Generalised Transduction

From the above diagram and notes:
a defective phage is one that contains bacterial DNA and no phage DNA.

At the end of the lytic cycle, viral DNA is being packed into the phage and so are some of the bacterial chromosome fragments. This packing error will give rise to some phages with viral DNA and others with only bacterial DNA. Size of the bacterial fragments will vary.
Since this defective phage does not contain viral DNA, (after adsorption and injection of the bacterial fragments into a new bacteria cell) no new bacteriophage is synthesized in the recipient bacterial cell.

Specialised Transduction

There is the lysogenic state and en face with an induction event, the excision of prophage is erroneous, removing a phage genome with some of its genetic material replaced by (particular) bacterial genetic material. The recombinant viral DNA that is produced this way is usually defective because some of its own genetic material is left behind.

This new circularized recombinant genome can still undergo replication because its origin of replication is intact and the DNA polymerase is non-discriminating  so you can get many of such DNA.

However, when the recombinant DNA is packaged within a capsid and the transducing particle injected it into a new bacterial cell, since part of the viral genome has been deleted, no progency virus can be formed in this bacterium because the necessary (viral) enzymes are not present*.
Recombination can take place as in diagram or there is integration of the DNA due to a common gene.


*this may be dependent on the site where the viral genome is cut, whether genes are removed. But usually they are and thus rendering the virus defective.





Specialised transduction


Examples of recombination close-up



Integration requires one-point




Recombination requires two-points





Diagram showing integration of F plasmid into bacterial chromosome.
Correct and Incorrect excision of F plasmid.

Updates I

I am sleep-deprived but so are quite a number of you, judging from your faces in classes.

Anyway, I have/will be giving out revision worksheets which I prepared last night. Most of the questions are from 10-years series except for Evol and bateria/virus because they are new in the syllabus so I scoured for them, drawing from different sources.

Why we are doing TYS? Because ultimately you are going to take the A's next year and sometimes there is a discrepancy in how schools and cambridge set their questions .I learnt that you all don't have enough exposure to TYS and let's not wait til the last mintue yah? And although the syllabus has changed, some have remained and I predicting that the deviation for some should not be too great for the first year. Oh well, there is no harm doing them right?

Questions are selected based on past experiences with students aka these are the more problematic MCQs for selected topics. Other than these, most should be okay - you would have to try them out yourself next time/next year? Right now, all these should serve as practice.

Answers will be posted later so that those coming for remedial can discuss them. But I think I will set it for as a test for one of the classes....?mmmm... will need to think hard.

Will be posting some bacterial diagrams later that we can all appreciate their recombination beauty.

Oh for 3L, I have started hatching the eggs yesterday:

Questions to consider

I am taking a hiatus after the multiple postings. "huff 2 puff 2"

Consider these random questions first which came to mind and students seemed to have trouble grasping during the course of teaching or hearsay (will post them in comments)

1) What are the purposes/functions of mRNA? (students on remedial should know)
2) What is the neutral theory about?


mmm......until more random snippets of thoughts self-generate or diffuse through from the school community....zzz......

Hope holidays have been good

Polymorphism

I probably need a revision on this question posted but...


Polymorphism is a form of genetic variation that exists as discontinuous e.g. blood groups in humans. There are distinct forms for a particular feature.

This, of course, is in contrast with continuous variation.

Where does energy for tail sheath contraction come from?

Since virus does not generate energy on its own, we are confounded by how the tail sheath contract. (out of syllabus)



One school of thought:

Hydrolysis of ATP stored in tail sheath upon conformation change.
(mentioned in this paper http://jb.asm.org/cgi/content/full/183/1/358)


Another school of thought:

There is a conformation change that involves a change in energy states (high to low) when the tail sheath contracts, thus favorable.

http://72.14.235.104/search?q=cache:fvBMMNlafq8J:bilbo.bio.purdue.edu/~viruswww/Rossmann_home/publ/pdfs/425.pdf+contraction+of+tail+sheath+energy&hl=en&gl=sg&ct=clnk&cd=9

Interesting.

What is an Antigen?

Taken off the net (which I find appropriate):


A substance capable of inducing an immune response. Exposure to this substance results in production of a specific antibody or a sensitized lymphocyte that in turn interacts with the antigen. In some autoimmune diseases, the body's own tissues may act as antigens.

Usually reference is made to proteins from foreign bodies (virus, bacteria etc) but (keep it at the back of your mind that) proteins of one self can be considered presented as antigens too, particularly during the development of our immune system so that our immune cells are primed to recognise our cells later on.

HIV - Transmission + Where does the HIV antibodies come from?

To become infected with HIV, the virus must be:
1) in sufficient quantity
2) enter the bloodstream

Thus, it is not enough to come into contact with an HIV-infected fluid to become infected. Healthy, unbroken skin does not allow HIV to get into the body; it is an excellent barrier to HIV infection. HIV can thus enter the bloodstream directly through an open cut or sore, or through contact with the mucous membranes (and transported across membranes) in the anus and rectum, the genitals, the mouth, and the eyes.

HIV can be more easily passed from person to person, through blood, sexual fluids i.e. seminal and vaginal fluids and breast milk where HIV tend to be concentrated, in following ways:

1.unprotected sexual intercourse with another infected person

Is HIV only transmitted via blood?
No. In the event of sexual intercourse:

Male to female transmission: Semen carrying HIV can enter the body of the female partner through the mucosal lining of the vagina, cervix and uterus.

Female to male transmission: Vaginal secretions carrying HIV can enter the body of the male partner through the head of the penis, the exposed urethra, or other cuts, sores or lesions on the penis.


2.sharing of infected needles and syringes (e.g. injecting drug users)
3.mother-to-child transmission during pregnancy, childbirth or breastfeeding


During pregnancy, there can be transplacental transmission of HIV virus. Mechanism is poorly understood though it may be due to particular receptors. (http://www.cahr-acrv.ca/english/resources/abstracts_2004/abs/abs236.htm) (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=retrieve&db=pubmed&list_uids=11745695&dopt=Abstract)

HIV is often passed on to the child during labour or delivery when there is direct contact with the mother's blood and bodily fluid. A caesarean section can apparently lower the risk. (note: Tutorial question examined the mutation of the virus after birth)


4.transfusion with contaminated blood or blood products




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The HIV Antibody Test detects whether proteins called antibodies,
which are produced in response to HIV, are found in the person's body.
Most people develop antibodies within 12 weeks of infection.
However, it is possible that the antibodies do not appear until six months
after the point of infection. This period of time when a person is infected
with HIV and has not developed antibodies to HIV is known as the
window period.
A positive result means that you are infected with HIV. You can infect others if you have sex with them.
A negative result means that you are either not infected or your infection was too recent to be detected. You need to repeat the test 3 months later.

But isn't the HIV latent? Where does the HIV antigens come from for the body's B cells to produce antibodies?

There is an inital phase when the HIV first enter the bloodstream and is active, causing a strong response from our immune system (thus all the antibodies) It is after that when it enter the latency period where by its number is low in the bloodstream but will persist in replication

(http://www.berkeley.edu/news/media/releases/2005/08/08_hiv.shtml) - quite a cool paper. Although the line of research is foreign to me but the concept is refreshing.

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(FYI)

HIV has been found in saliva and tears in very low quantities from some AIDS patients. It is important to understand that finding a small amount of HIV in a body fluid does not necessarily mean that HIV can be transmitted by that body fluid. Contact with saliva, tears, or sweat has never been shown to result in transmission of HIV.

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Does Oral Sex confer transmission of HIV?

Oral sex carries a lower risk, but again HIV transmission can occur here if a condom is not used - for example, if one partner has bleeding gums or an open cut, however small, in their mouth.

See study below.
The study was done on men-men relationship. However it should be noted that there is a much greater incidence of HIV transmission in a hetero-relationship. HIV is not a gay disease.

http://www.cdc.gov/hiv/resources/factsheets/oralsexqa.htm

Prophage: genome or entire cell?

Prophage: phage GENOME which is integrated into the bacterial chromosome. Upon the occurence of an induction event, the prophage is exercised from the bacterial chromosome.
Prophage is also considered as the latent form of a bacteriophage.

Where do the bacteria in our intestines (microflora) come from?

http://www.all-creatures.org/health/beneficial.html


Before birth the gastrointestinal tract of a normal fetus is sterile. During the birth process the newborn is inoculated, by passage through the birth canal, with organisms from the mother’s vagina and bowel.

Benefits to the infant begin immediately with this natural defense barrier of “friendly” bacteria standing against harmful microbes that will enter later on with touching, suckling, kissing, and caressing. The importance of this early invasion should not be underestimated. This initial invasion makes a permanent impression on our immune systems, thereby affecting a person’s well-being throughout his or her life.

Newborns delivered by cesarean section do not get a healthy dose of mother’s bacteria. Born through the abdomen, much of their initial bacteria come from the unhygienic environment of a hospital. However, this setback can be remedied by the initiation of proper infant feeding after birth – and helped by the addition of infant probiotics (see below).

Breast feeding encourages the growth of “friendly” bacteria known as Bifidobacterium. These vital organisms protect the baby from gastrointestinal infections that can result in illnesses severe enough to require hospitalization, and sometimes cause death. Mother’s milk contains sugars (galacto-oligosaccharides) which encourage the growth of these friendly bacteria. By the fourth day of life, Bifidobacterium represent 48% of the bacteria in breast-fed infants as opposed to 15% in bottle-fed infants.4 Eventually, over 95% of the bacteria become Bifidobacterium bacteria in an exclusively breast-fed baby. Introduction of small amounts of formula to a breast-fed baby will result in shifts from a breast-fed to a formula-fed pattern of the microflora. After weaning from breast milk – ideally after the age of 2 years – the child’s flora become similar to an adult’s.

Change the Diet – Change the Microflora

The partially digested remnants of our meals, after arrival in our large intestines, become the foods for our microflora. Each species of bacteria survives best on specific kinds of nutrients. In short, “friendly” bacteria prefer to dine on plant-food remnants, and pathogens thrive when the diet is low in plant foods and high in meat and other “junk-food.” Therefore, what we choose to eat determines the predominance of the bacteria species that will live in our gut. By changing from a diet based on animal- and highly processed-foods to whole plant-foods, you can suppress the growth of harmful bacteria and stimulate those that are beneficial. Major alterations in the microflora take place within one to two weeks of changing a person’s diet.

What does CAP binding protein do?

Finally. After two days of ceaseless typing and meandering through excessive information, your new set of notes for lecture is ready for collection. Bio rep please collect on Mon morning... I am brain dead....almost.

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Finally can get down to reply to the loads of fan mail that lies before me and sort out a series of questions in my head.

Disclaimer: All info published are based on current understanding.


Function of CAP binding protein in lac operon:

Lac operon has a weak promoter (low in efficiency). When bound to DNA, CAP bp-cAMP complex will increase the affinity of promoter region for RNA polymerase - this is done through an almost 90 degrees bending of DNA which allow CAP to directly interact with the polymerase at the promoter.

Consultation + Polycistronic versus?

moe email is back on service.

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I am back on a vengence.
Please note that as the moe account has been facing many trouble since its apparent facelit on 1 Sept thus if you are coming for consultation, kindly send/resend a mail to XXXX instead or just post a comment - it will reach me.

Those who I am meeting tomorrow - cya.

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Polycistronic mRNA - refers to mRNA which will give rise to many polypeptide chains i.e. many genes encoded within it

versus

Monocistronic mRNA - refers to mRNA which only give rise to ONE polypeptide chain i.e. one mRNA - one gene - one polypeptide; this is typical of eukaryotic cells.

Will be talking about it soon.

The rest of the questions will be tackled soon - need to rush something out by Fri

He-li-O

I decided to set up this site to share knowledge with everyone in my classes, in particular to deal with interesting questions and concepts that have been raised up by students, some of which may not be in the syllabus but are interesting learning points. (And I can get it down in print before I forget to get back to students=P) It also includes questions which flash through my boggled mind once in a while or to clarify issues present in class.

Biology is really about life . There was a period of time when I wanted to focus on cell and molecular work, only to take a step back and say, I want to know more about life in general as well otherwise my education in the field is not complete. Biology is huge and your teacher is not enlightened yet but will try his best to direct your path to the end of the tunnel where the light is.

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Please note:

Consultation during the September holidays will take place from Thurs - Sat (12-4pm)
Do let me know if you are coming down via email: chan_huang_kiat@moe.edu.sg otherwise I might not come down to school.
I might not be able to reply you readily because I will be away til Wed morning. My apologies but I will be down on Thurs definitely.
Do let me know if you need to see me beyond the above time slot.

Cheers for the mugging.

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There are some running questions in my head now. Will post them once I have the time. It is a busy holiday too. :P