Biology SL/HL help

[Licorice]

No they're not, for example in 2.5.4 you're going to mention things like "chromatin condenses together into a chromosome". However, that has got nothing to do with the fact that mitosis produces two genetically identical nuclei. What ensures that is the fact that sister chromatids (i.e the other copy of the DNA that was replicated in interphase) are pulled apart so that each one goes into a cell, which is what happens with all 23 chromosomes. By the end of Anaphase, you have a copy of each chromosome on each pole of the cell. That's what produces two genetically identical nuclei from mitosis.

Yes it looks the same, but in the second one they are only looking for the part where sister chromatids are seperated.

Aha, it's clearer now, I think I actually get it this time! For me, the confusion came from the fact that what I was supposed to write in 2.5.5, I had already mentioned in 2.5.4... Anyway, thank youu:D

[Proletariat]

If just meiosis, and not fertilization (which would be obvious), then it would be crossing over and nondisjunction.

Since it is eight points, they are likely looking for explanations on the processes of the two.

(Yes, I'm being purposefully cagey.)

[Drake Glau]

If just meiosis, and not fertilization (which would be obvious), then it would be crossing over and nondisjunction.

Since it is eight points, they are likely looking for explanations on the processes of the two.

(Yes, I'm being purposefully cagey.)

And independent assortment. Always a good one

[Marija Vaitkevi�ienė]

Ne~~~, I was wondering - how does one distinguish, which host cells adopted the recombinant plasmid with a desired protein-coding gene, while all of the plasmids used for engineering have uncut antibiotic resistance sites? That is, I used an enzyme which did not inactivate any site and which cut least of additional sequences of the DNA strand apart from the object gene.

There is no other marker, though, none, which would make the colonies, for example, blue or white (mcgraw-hill animations, yeah...). And if so, what would a cut, that is, inactivated antibiotic resistance site do good? In any case, if antibiotics are applied, we would only get to see which cells in a particular petri plate DID NOT adopt the recombinant plasmids, not talking about the host cells which adopted the recombinant plasmids containing undesired genes.

But then... Then wtf?

Do I have to start thinking that there is something wrong with me for imagining things or is there something I do not know? Tell me, very pretty please T.T

[Mahuta ♥]

You got me very confused there, haha.

I am not very clear about what you're asking, but all you need to know about plasmids and recombinant(..etc) is:

4.8.8: Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase.

The syllabus says you need to know this:

"The use of E. coli: Most of its DNA is in one circular chromosome, but it also has plasmids (smaller circles of DNA). These plasmids can be removed and cleaved by restriction enzymes at target sequences. DNA fragments from another organism can also be cleaved by the same restriction enzyme, and these pieces can be added to the open plasmid and spliced together by ligase. The recombinant plasmids formed can be inserted into new host cells and cloned."

That's all you need to understand, don't confuse yourself with these things. Once you understand the above very well then you can look for more answers. Though to be honest, it is a bit confusing and unless you have a lot of free time..don't waste your time nothing more than the above will be on the exam.

[BatMite]

Hey, I have a really big problem in drawing the heart diagram, especially the ones found in textbooks and guides with all the veins and arteries mixed up together, so I was wondering, is this picture fine to draw and get a full grade on in an IB Biology exam: http://upload.wikimedia.org/wikipedia/commons/1/1c/Heart_diagram_corrected_labels.JPG ?

or does it have to be a picture like this:

http://4.bp.blogspot.com/_L6W6V1A_AyA/S_aJIP_zB1I/AAAAAAAAAVY/6LZw-jWx1Bg/s1600/human_heart_diagram.gif

If I can only draw something like the 2nd picture, does anyone have any tips on how to draw a heart like that, mine are just so mixed up...

[Mahuta ♥]

The second one will be fine, and just start out with the outside, then go up in the middle and draw the wall between the atriums and ventricles. You would have an outline of the pulmonary artery, the aorta and the veines, you just have to draw the other side of the wall and the valves.

This is a very shaky and bad picture, but you get the point. Make sure to draw the wall of the left ventricle to be thicker than that of the right one.

This is missing, labels or arteries, veins and chambers and obviously the lines need to look neater and all. Just a very rough drawing.

[BatMite]

The second one will be fine, and just start out with the outside, then go up in the middle and draw the wall between the atriums and ventricles. You would have an outline of the pulmonary artery, the aorta and the veines, you just have to draw the other side of the wall and the valves.

This is a very shaky and bad picture, but you get the point. Make sure to draw the wall of the left ventricle to be thicker than that of the right one.

This is missing, labels or arteries, veins and chambers and obviously the lines need to look neater and all. Just a very rough drawing.

Thanks! So I guess this one works fine: http://upload.wikimedia.org/wikipedia/commons/1/1c/Heart_diagram_corrected_labels.JPG

Thank you for the drawing too!!

[Mahuta ♥]

BatMite: Yup that picture is just fine.

[IBavictim]

Hi, I don't have notes on long-day/short-day plants. I need some help on answering this =)(Not surpringly, it's plant science haha. I find it boring! >_< )

9.3.6 Explain how flowering is controlled in long-day and short-day plants.

Teacher's Notes: Limit this to the conversion of Pr (red absorbing) to Pfr(far-red absorbing) in red or white light, the gradual reversion of Pfr to Pr in darkness, and the action of Pfr as a promoter of flowering in long-day plants and an inhibitor of flowering in short-day plants.

(I really don't understand what I'm supposed to say )

Thanks in advance!

I've also got another question about studying for the Bio HL exam =)

I will be done answering each question on the syllabus (options included) by tomorrow afternoon(Sunday, 15th). After that, I've got 44 hours (From Monday, Tuesday and 5 hours before the afternoon exam Paper 1 and 2. 44 hours because I'll be getting about 4 hours of sleep on Monday and Tuesday if I have to. I'll sleep 9 hours the night before the Wednesday exam though! )

Do you think this is enough? —I know it's too late if you say no, it isn't enough... but I'd like an idea of how I would do for the exams this way >_<"

I think I've still got information stored from my long term memory (especially from my favourite topics! )

Edited May 15, 2011 by Mahuta ♥

[Mahuta ♥]

*Topic 9 Plant science- 9.3.6 Control of flowering in short/long day plants*

Haha I did not like plants either, but it's not that hard to understand.

First of all, you need to understand the following:

• Long day plants need short night (in the summer), Short day plants need long night (winter).
  
• Flowering is controlled by phytochrome pigment-responds to night length.
  
• There are 2 forms of phytochrome:P_Rand P_FR(unstable/active).
  
• P_R turns into P_FR in daylight as it absorbs lots of 'red light'.
  
• P_FR turns back into P_Ras it breaks down at night.
  
• Basically, the night length determines the amount of P_FR left.
  

For long day plants:

• Night is short, so lots of P_FRleft.
  
• This stimulates flowering by attaching to a protein which switches on the flowering gene.
  

For short day plants:

• Night is long, so P_FR is broken down.
  
• P_FR inhibits the protein (that switched on gene).
  
• So, as the night gets longer, more P_FR is broken down, so very little is left to inhibit the protein.
  
• When there isn't enough P_FR to inhibit, flowering starts.
  

---

For your second point:

You sound absolutely ready to me, if you've done all the past papers you could come across! Also, long term memory from your favorite topics is definitely a good thing, it helped me a lot in the exams. That being said, do not ignore them when you're revising for the last time before the exam. Make sure you go through everything before the exam, even if you didn't have time, reading it is enough, assuming you understand it very well.

[Hammerdown]

Which of the following represents a test cross to determine if phenotype T is homozygous or

heterozygous? (Note: allele T is dominant to allele t.)

A. Phenotype T crossed with another phenotype T

B. Phenotype T crossed with a phenotype T which is homozygous

C. Phenotype T crossed with a phenotype T which is heterozygous

D. Phenotype T crossed with phenotype t

My answer was B but i am wrong, i do not get it

[Drake Glau]

C, test cross is always heterozygous dominant.

[Hammerdown]

unfortunately the answer is D

[Drake Glau]

unfortunately the answer is D

This is why i hate genetics! OMG!

K, yes, D, test crosses cross with a heterozygous recessive form. Sorry. Making the phenotype t correct.

Genetics.

Ecology

Evolution

They're going to kill me...

Edited May 17, 2011 by Drake Glau

[Hammerdown]

unfortunately the answer is D

This is why i hate genetics! OMG!

K, yes, D, test crosses cross with a heterozygous recessive form. Sorry. Making the phenotype t correct.

Genetics.

Ecology

Evolution

They're going to kill me...

lol you and me both

[Nemandi]

Hi, do we need to know lac operon and chi square test for May 2011 exam? Thanks.

Edited May 17, 2011 by Nemandi

[suggaplum]

Hi, do we need to know lac operon and chi square test for May 2011 exam? Thanks.

No we do not need to know lac operon for the exams and probably chi square as well. However, if chi squared is really on the exam, it will only be probably on paper 1

[ConfusedIBer]

Any guesses on potential questions for Paper 2?

[Mahuta ♥]

Trust me no point guessing, just do lots of past papers and if you're lucky there are going to be questions you came across while doing them.

All I can tell you is for section B, you may want to go over all the long processes in the syllabus like:

• Spermatogenesis.
  
• Ovogenesis.
  
• Comparison of the two above.
  
• Light dependent reaction.
  
• Light independent reaction (Calvin Cycle)
  
• Kreb's cycle.
  
• Oxydative Phosphorylation.
  
• Muscle contraction.
  
• The role of hormone X in the menstrual cycle.