BIOL335

Hello 335 students!

For those who asked...I am doing T02 in room 2449.

Cheers

Pam

(By the way...anyone could come up with an answer for that crazy pedigree/3 genes question?)

ALL THE BEST, 'BIOL334 GRADUATES'!

Dear BIOL334 graduates,

have a great summer and best wishes for your future academic and professional careers!

It was a pleasure to work with such an enthusiastic and inquisitive group. 

By the way, remember the anonymous meiosis diagrams that you drew on the first day? They will be on the internet soon--I'll post the URL here.

Cheers,

Pam

(PS: if you have an answer to the black/white/striped pedigree question, and you'd like to share it, just let me know! If not, the answer that I'd consider the simplest one may at some point make an appearance on this blog).

The white, black and striped problem

Hello BIOL334 students!

Some of you were very eager to know the answer to the craziest pedigree/gene interaction question that you'll ever see...but I don't want to spoil the fun for everybody else. So, here are a few hints towards the explanation that I find the simplest (but is in no way the only one). PLEASE REALIZE that it's about 5 times harder than a 334-level question, and you did an absolutely fantastic job trying to work it out. You shouldn't fear integrated gene interaction questions anymore!!

HINTS
I'll use symbols B and D for the 2 genes that we all agreed upon, and will define the phenotypes in the following way:

B-D- is black, bbD- is striped and B-dd is white (I hope I remember our pedigree explanation correctly).
The cross B-D- X bbDD gives us:
50% white
10% striped
40% black

We said that it won't (easily) work with 2 genes involved, so we'll have to invoke a 3rd gene... and the 'restrictions' are:
- we need to form a 'new' phenotype in the progeny (that was not seen in the parents)
- we need to make 50% of the progeny of that new phenotype

Remember that, in the world, genes can have more than 2 alleles!
Remember that the pure line needs to be a pure line!
Remember that it IS possible to create novel allelic combinations in the progeny, even with respect to only one gene (remember black X cream gave us some sepia? All with ONE gene!)
Remember that one allelic combination (relative to one gene) can be epistatic to 'everything' else!
Also, notice that all the offspring will be D-, so the white individuals won't be white because of 'dd'. We have to have an alternative way to produce white, and at this point we can disregard D(d) in the analysis, because in this scenario it is now irrelevant.

Have fun and all the best on your final!

Pam

POPULATION GENETICS

Please post here all the questions you have regarding population genetics.

Check out the paper-saving page; there will be (as of 10am today) some practice questions on pop gen...

Today we will work on quantitative genetics (bring the handout!) and Thursday we'll have a review session.

Cheers

Pam

CHROMOSOMAL REARRANGEMENTS AND EXTRA QUESTIONS

Several people asked for additional practice questions: I have added a few (quite challenging ones!) on the Paper-saving page, and you'll find more on my loppins blog.

PLEASE POST HERE ALL YOUR QUESTIONS ON INVERSIONS!

REGARDING CHROMOSOMAL REARRANGEMENTS WE SAID...

Assumptions for diploids in BIOL334=> we only deal with rearrangements that do NOT BREAK genes.

The main things to remember are that:

- at meiosis, homologous bits of chromosome do anything it takes to pair up;

- if a rearrangement involves a very small portion of a chormosome (at the base-pairs scale), the energy required to 'twist and bend' in order to pair is too high, so that region will just stay unpaired

- once you figure out what the chromosomes look like as they are paired up at meiosis, you can start predicting what will be the consequences of no crossovers, crossovers in a given region, crossovers in a different region, etc.

Generally speaking... 

A homozygous for a chromosomal rearrangement will produce all viable gametes, regardless of where crossovers happen (pairing does not require 'twisting, bending, and looping' of chromosomes);

A heterozygous for a large enough inversion will produce some viable and some lethal gametes (i.e. will have decreased fertility). Single/odd numbers of crossovers within the inverted region result in non-viable gametes. From a RF perspective, the RF between genes that are on either side of the inverted region will be decreased.

TRANSLOCATIONS will be discussed on Friday.

Cheers

Pam

Mapping in bacteria and gene interaction in diploids

Below is some information (that you may or may not find useful) on 'gene interaction', and on the paper-saving page you'll find some notes, tips and tricks on mapping in bacteria and on suppression in haploids (both heterodimer suppression and non-heterodimer supppression).

If you have any questions regarding these topics, please post them here (use the 'comments' feature).

Cheers

Pam

About three-points testcrosses...

Below is another practice quesiton for you! You should be able to solve it in about 15 minutes.

Great questions from your textbook include:

Chapter 4 #11, 12 13, 48, 49 and 42: determining genotypes, allelic configurations and map distances from a scenario and a data set;

Chapter 4 #37, 50, 56, 51: predicting genotypic and phenotypic frequencies from a testcross given the map distances and the genotype of the trihybrid;

Chapter 4 #54 and 36: dealing with 4 genes.

Also, check out the 'paper-saving page' for more info on 3 points tescrosses.

Cheers

Pam