Biology Exam Chat + Exam Copy + Answers (now)

[simpak]

Maybe I should do biol again next year since i don't have a 5th subject and I did so crap on this exam!

Don't redo subs.

[jane1234]

stem cell mcq was C - can be extracted from 2-4 cell embryo right?

also that question on olws was terrible, lol they are gonna have fun trying to set the marking scheme

Think so. Wouldn't have been D because it said stem cells only differentiate into a LIMITED number of cell types...

[Charmz]

IF OWLS IS A GENE - IT IS 1/2

IF OWLS IS AN ALLELE - IT IS 1/4

FUCKING

FUCKING


DOES NOT INDICATE THOSE PIECE OF SHIT

What? OLWS couldn't have been a gene... it was a condition/disease.. and it wouldn't have mattered if the condition was recessive or dominant, cause you would have gotten the same outcome answer
unless im missing something pretty big..

http://en.wikipedia.org/wiki/Lethal_white_syndrome#Homozygotes

[Charmz]

Maybe I should do biol again next year since i don't have a 5th subject and I did so crap on this exam!

Don't redo subs.

why not?

[simpak]

Maybe I should do biol again next year since i don't have a 5th subject and I did so crap on this exam!

Don't redo subs.

why not?

Because it's often just a waste of time - anyone I know who has repeated has gotten a very similar score, unless you need the subject to be >a certain raw for whatever reason it's best to just take something else?  Look at my Year 11 sub...

[Panicmode]

The gene that controls OWLS was made up of two alleles;

O - does not have OWLS
o - has OWLS

For the purpose of this bio exam and with the information given, this was the most valid assumption

"Lethal white syndrome can be described as recessive because heterozygotes (written Oo or N/O) are not affected by intestinal agangliosis"

It must be an allele because it says she is heterozygous for that condition

If she is heterozygous and alive, it means she is an unaffected carrier. Therefore, the probabilty of a foal not coming to term is 1/4

The second part of this question is therefore, 9/16 as when a suitable di-hybrid cross is drawn, it is shown that 9/16 foal will be phenotypically normal (hence the massive space they gave us)

Or alternitvely; Pr(not affected by HERDS) = 3/4
Pr(not affected by OWLS) = 3/4
Pr (not affected by HERDS n not affected by OWLS) = Pr(not affected by HERDS) x Pr(not affected by OWLS)
= 3/4 x 3/4
= 9/16

[Charmz]

Maybe I should do biol again next year since i don't have a 5th subject and I did so crap on this exam!

Don't redo subs.

why not?

Because it's often just a waste of time - anyone I know who has repeated has gotten a very similar score, unless you need the subject to be >a certain raw for whatever reason it's best to just take something else?  Look at my Year 11 sub...

Thanks that makes me feel heaps better

[simpak]

when you say it like that... it sounds convincing... but ...

Let me put this to you another way.  It has to be a recessive lethal, with the genotype oo resulting in the lethality and not OO because that would mean every horse birth would have a mortality rate of 50% (if you're suggesting only an Oo horse could survive, only Oo x Oo would mate and therefore 50% would either be oo or OO).  Clearly we don't observe this in every day life.

Secondly, thinking of this in terms of gene product it's not really plausible that only the heterozygote would survive.

[Charmz]

The gene that controls OWLS was made up of two alleles;

O - does not have OWLS
o - has OWLS

For the purpose of this bio exam and with the information given, this was the most valid assumption

"Lethal white syndrome can be described as recessive because heterozygotes (written Oo or N/O) are not affected by intestinal agangliosis"

It must be an allele because it says she is heterozygous for that condition

If she is heterozygous and alive, it means she is an unaffected carrier. Therefore, the probabilty of a foal not coming to term is 1/4

The second part of this question is therefore, 9/16 as when a suitable di-hybrid cross is drawn, it is shown that 9/16 foal will be phenotypically normal (hence the massive space they gave us)

Or alternitvely; Pr(not affected by HERDS) = 3/4
Pr(not affected by OWLS) = 3/4
Pr (not affected by HERDS n not affected by OWLS) = Pr(not affected by HERDS) x Pr(not affected by OWLS)
= 3/4 x 3/4
= 9/16

As much as I want you to be right because I wrote the same thing, it's not correct.

[simpak]

Maybe I should do biol again next year since i don't have a 5th subject and I did so crap on this exam!

Don't redo subs.

why not?

Because it's often just a waste of time - anyone I know who has repeated has gotten a very similar score, unless you need the subject to be >a certain raw for whatever reason it's best to just take something else?  Look at my Year 11 sub...

Thanks that makes me feel heaps better

Np, that's why I leave such an embarrassing score in my sig

[lilmamba17]

Think so. Wouldn't have been D because it said stem cells only differentiate into a LIMITED number of cell types...
[/quote]

Yeah and in jacaranda says the totipotent can be extracted from 2-4-8 cell embryos

[Panicmode]

The gene that controls OWLS was made up of two alleles;

O - does not have OWLS
o - has OWLS

For the purpose of this bio exam and with the information given, this was the most valid assumption

"Lethal white syndrome can be described as recessive because heterozygotes (written Oo or N/O) are not affected by intestinal agangliosis"

It must be an allele because it says she is heterozygous for that condition

If she is heterozygous and alive, it means she is an unaffected carrier. Therefore, the probabilty of a foal not coming to term is 1/4

The second part of this question is therefore, 9/16 as when a suitable di-hybrid cross is drawn, it is shown that 9/16 foal will be phenotypically normal (hence the massive space they gave us)

Or alternitvely; Pr(not affected by HERDS) = 3/4
Pr(not affected by OWLS) = 3/4
Pr (not affected by HERDS n not affected by OWLS) = Pr(not affected by HERDS) x Pr(not affected by OWLS)
= 3/4 x 3/4
= 9/16

As much as I want you to be right because I wrote the same thing, it's not correct.

Lol what? What was the answer then?

Also, pretty sure the answer was C because totipotent stem cells can differentiate into any cell.

[Charmz]

when you say it like that... it sounds convincing... but ...

Let me put this to you another way.  It has to be a recessive lethal, with the genotype oo resulting in the lethality and not OO because that would mean every horse birth would have a mortality rate of 50% (if you're suggesting only an Oo horse could survive, only Oo x Oo would mate and therefore 50% would either be oo or OO).  Clearly we don't observe this in every day life.

Secondly, thinking of this in terms of gene product it's not really plausible that only the heterozygote would survive.

According to wikipedia, all homozygous, recessive or dominant, die.

'Lethal white syndrome has been described by researchers as both dominantly-inherited and recessively inherited. Lethal white syndrome can be described as recessive because heterozygotes (written Oo or N/O) are not affected by intestinal agangliosis. The term "carrier", by definition, applies only to recessive conditions. However, if the frame pattern trait is included in the lethal white syndrome, inheritance of the trait follows an incomplete dominant pattern. It should be noted that the concept of "recessive" and "dominant" predate molecular biology and technically apply only to traits, not to genes themselves. In pleiotropic conditions, such as lethal white syndrome, the application of "recessive" or "dominant" can be ambiguous.'

Plus the question does not state whether it is dominant or recessive. You'd think it would be stated but after re-reading the question, there is not doubt that it is both dominant and recessive which die.

[WhoTookMyUsername]

yeah was C, that was a tough one though, 3 of them at first glance seemed right


i think it should be 50%
and 1/2 x 3/4 = 3/8

after exam went and bought literally $20 of chips from coles ... WHY!!!

[Charmz]

The gene that controls OWLS was made up of two alleles;

O - does not have OWLS
o - has OWLS

For the purpose of this bio exam and with the information given, this was the most valid assumption

"Lethal white syndrome can be described as recessive because heterozygotes (written Oo or N/O) are not affected by intestinal agangliosis"

It must be an allele because it says she is heterozygous for that condition

If she is heterozygous and alive, it means she is an unaffected carrier. Therefore, the probabilty of a foal not coming to term is 1/4

The second part of this question is therefore, 9/16 as when a suitable di-hybrid cross is drawn, it is shown that 9/16 foal will be phenotypically normal (hence the massive space they gave us)

Or alternitvely; Pr(not affected by HERDS) = 3/4
Pr(not affected by OWLS) = 3/4
Pr (not affected by HERDS n not affected by OWLS) = Pr(not affected by HERDS) x Pr(not affected by OWLS)
= 3/4 x 3/4
= 9/16

As much as I want you to be right because I wrote the same thing, it's not correct.

Lol what? What was the answer then?

Also, pretty sure the answer was C because totipotent stem cells can differentiate into any cell.

The key word was limited not any so that option was incorrect.