biology paper 1 doubts

[Ashiq Sookarry]

Actually less negative refers to a higher water potential. And more negative to a lower water potential as it contains more solutes. Adding to solutes to pure water lowers the water potential.

 

[nelly trich]

Option 1 cannot be correct because during the formation of the bee sperm cells, the diploid cell undergoes meiosis to halve the number of chromosomes which results in genetically different cells.[/quo
thus you're not agreeing with statement 2 ? which is right !

 

[ZohaibAsad]

The simple answer to this is that being haploid does not mean that there is no genetic variation it is just a statement to refer to the number of chromosomes. If there is no genetic variation then the situation is referred to as `homoploid`. Hence, 1 cannot be right so the answer is C.

 

[nelly trich]

The simple answer to this is that being haploid does not mean that there is no genetic variation it is just a statement to refer to the number of chromosomes. If there is no genetic variation then the situation is referred to as `homoploid`. Hence, 1 cannot be right so the answer is C.

how come you remove statement 2 from your interperation ,sperm cells are produced by mitosis ,mitosis produces identical cells to the mother cells ! can you please clearify this for me ? and also he said develop from unfertilised eggs meaning that it's asexual reproduction

 

[ZohaibAsad]

how come you remove statement 2 from your interperation ,sperm cells are produced by mitosis ,mitosis produces identical cells to the mother cells ! can you please clearify this for me ? and also he said develop from unfertilised eggs meaning that it's asexual reproduction

Your implicit assumption regarding the parent in: ",mitosis produces identical cells to the mother cells " is partially incorrect. Read through the lines below to refine the concept of haploid.

The haploid number (n) is the number of chromosomes in a gamete of an individual. This is distinct from the monoploid number (x), which is the number of unique chromosomes in a single complete set. Gametes (sperm, and ova) are haploid cells.

The question didn't specify the parent's set of chromosomes so male bees from one set of chromosomes of a parent will have the same genetic information, another from an entirely different parent will have different genetic information from the other set although they have the same genetic information within their own set.

The rule is, to only derive conclusions from the info given as it is rather than generalize it. With that reasoning only statements 2 and 3 can be directly concluded.

 

[scarface007]

http://olevel.sourceforge.net/papers/9700/9700_s12_qp_11.pdf
question no. 22
how come the answer is 20 amino acid (A) and not 40 amino acid (B)?

 

[xtremeforums]

may/june 08. Q27.
Why is the answer C and not A?
i understand that lignin is absent.
But why is the solute potential low?
phloem sieve tubes have sucrose, which lowers the water potential, so the sucrose potential should be higher right?
Thanks...

 

[xtremeforums]

http://olevel.sourceforge.net/papers/9700/9700_s12_qp_11.pdf
question no. 22
how come the answer is 20 amino acid (A) and not 40 amino acid (B)?

A DNA molecule is double stranded. And only one strand is used as a template for transcription. So 120/2=60. This would give you the number of nucleotides on one strand of the DNA.
3 codons on the mRNA code for one amino acid. So 60 would code for how many aminoacids? Cross multiply. 60/3=20 amino acids.

 

[scarface007]

A DNA molecule is double stranded. And only one strand is used as a template for transcription. So 120/2=60. This would give you the number of nucleotides on one strand of the DNA.
3 codons on the mRNA code for one amino acid. So 60 would code for how many aminoacids? Cross multiply. 60/3=20 amino acids.

thanks a million

 

[ZohaibAsad]

http://olevel.sourceforge.net/papers/9700/9700_s12_qp_11.pdf
question no. 22
how come the answer is 20 amino acid (A) and not 40 amino acid (B)?

120 nucleotides involved on the DNA strand. For polypeptide formation mRNA must be created. Split the DNA into half

That makes 120/2 = 60 on each side

Total number of different base pairs involved in coding: A-T, A-U, C-G = 3

60/3 = 20

 

[scarface007]

120 nucleotides involved on the DNA strand. For polypeptide formation mRNA must be created. Split the DNA into half

That makes 120/2 = 60 on each side

Total number of different base pairs involved in coding: A-T, A-U, C-G = 3

60/3 = 20

hmm got it thanks

 

[externityxzx]

17 In which process does mitosis not have an important role in living things?
A asexual reproduction
B growth of cells
C increase in size
D repair to damaged tissues
i answered C but the correct answer is B! i dont get this question...
also http://olevel.sourceforge.net/papers/9700/9700_s12_qp_11.pdf
question 16 i dont understand the question

 

[aiskw1]

Q 17) B - it's not the growth of cells but the growth in the whole organism itself

and for question 16 it's in the previous pages on the thread

think of it this way

oxygen is required for active transport, with nitrogen bubbled there would be no oxygen... now you find out which one it is! or requires oxygen!

 

[aiskw1]

What bonds are there in a DNA molecule?

1) Covalent Bonds (tick)
2) Hydrogen Bonds (tick)
3) Disulfide Bonds (?, probably no?)
4) Ionic Bonds (really not sure)
5) Hydrophobic interactions (tick)

and where does phosphodiester bonds fit in? are they covalent bonds?

 

[ZohaibAsad]

It's a secondary structure. Phosphodiester bonds are actually covalent bonds between phosphates and ribose sugars

 

[athaan]

What bonds are there in a DNA molecule?

1) Covalent Bonds (tick)
2) Hydrogen Bonds (tick)
3) Disulfide Bonds (?, probably no?)
4) Ionic Bonds (really not sure)
5) Hydrophobic interactions (tick)

and where does phosphodiester bonds fit in? are they covalent bonds?

Yes, phosphodiester bond is covalent bond (cmiiw). I guess disulfide isn't present.

 

[ZohaibAsad]

17 In which process does mitosis not have an important role in living things?
A asexual reproduction
B growth of cells
C increase in size
D repair to damaged tissues
i answered C but the correct answer is B! i dont get this question...
also http://olevel.sourceforge.net/papers/9700/9700_s12_qp_11.pdf
question 16 i dont understand the question

Think of cells that can't undergoe mitosis but still grow. Hence, option B ruled out. C happens in cancerous tissues, D happens in skin repair A happens in plant and animal reproduction, B is not a necessary condition since it's not always true.

 

[Ashiq Sookarry]

only hydrogen bonds between complementary base pairs and covalent bonding for the phosphoester linkage.

 

[Ashiq Sookarry]

For number 17 i think C is the answer. Because it said increase in size. it has not mentioned increase in size of what.

 

[externityxzx]

thanks!! i understand it now