quick question

[cipherpol]

The table below shows the chromosome number of commercially grown cultivars:

Organism       Polyploid number     Chromosome number
Banana                  3N                    27
Strawberry             8N                    56
Common Wheat       6N                    42
Boysenberry           7N                    49

It would be expected that:
A. gametes of the strawberry would contain 14 chromosomes
B. the haploid number for wheat is 7
C. bananas and boysenberries are sterile and can't be reproduced
D. the diploid number for wheat is 21

I answered B, but the correct answer is C. I understand that you can't divide 3N and 7N into two parts, but why isn't B correct as well? (unless my definition of haploid is wrong)

Thanks.

[Edmund]

For Common Wheat, haploid would be 3N (not N), so the chromosome number of the haploid would be 21.

[cipherpol]

For Common Wheat, haploid would be 3N (not N), so the chromosome number of the haploid would be 21.

Gah, so haploid refers to half of polyploid number? I always thought it meant one set of chromosomes.

[scar]

Wheat has 42 chromosomes per cell.  (whether it is 2N, 8N or 20N is irrelevant)  Meiosis produces cells with HALF the number of chromosomes as a somatic cell.  That way when sperm meets egg they add up to the normal amount.  1/2 + 1/2 = whole.  I can see where the term Haploid is confusing though - only really relevant when the original is normal diploid not polyploid. Hope this helps.

[cipherpol]

another question; does helicase unzip DNA so that transcription can occur, or is it a different enzyme?

[shinny]

another question; does helicase unzip DNA so that transcription can occur, or is it a different enzyme?

RNA polymerase (RNA polymerase II to be specific) unzips the DNA in transcription, as well as doing its better known role of matching base pairs.

[shinny]

another question; does helicase unzip DNA so that transcription can occur, or is it a different enzyme?

RNA polymerase (RNA polymerase II to be specific) unzips the DNA in transcription, as well as doing its better known role of matching base pairs.

i've always been told its Helicase oh actually that might be for DNA replication.

Yeh, helicase only operates in DNA replication.

[qshyrn]

another question; does helicase unzip DNA so that transcription can occur, or is it a different enzyme?

RNA polymerase (RNA polymerase II to be specific) unzips the DNA in transcription, as well as doing its better known role of matching base pairs.

wow, just learnt something new.
I swear we've never been taught that. i dont think ive encountered it in the textbook as well (i think it just says the dna unwinds)

[shinny]

another question; does helicase unzip DNA so that transcription can occur, or is it a different enzyme?

RNA polymerase (RNA polymerase II to be specific) unzips the DNA in transcription, as well as doing its better known role of matching base pairs.

wow, just learnt something new.
I swear we've never been taught that. i dont think ive encountered it in the textbook as well (i think it just says the dna unwinds)

Hmm...this is something that was specifically pointed out to me even at a VCE level, not just uni =S

[cipherpol]

another question; does helicase unzip DNA so that transcription can occur, or is it a different enzyme?

RNA polymerase (RNA polymerase II to be specific) unzips the DNA in transcription, as well as doing its better known role of matching base pairs.

wow, just learnt something new.
I swear we've never been taught that. i dont think ive encountered it in the textbook as well (i think it just says the dna unwinds)

Hmm...this is something that was specifically pointed out to me even at a VCE level, not just uni =S

guess my teacher and textbook sucks ._.

[TrueLight]

lol yeah it doesn't need the help of helicase to unwind... rna polymerase 1 syntheisizes rrna and 3 syntheisizes trna, so rna polymerase 2 with the help of transcription factors and other promoter elements recognizes, binds, unwinds and transcribes dna

[cipherpol]

so essentially, RNA polymerase II just reads the bases while RNA polymerase I synthesizes the pre-mRNA?

edit: just confirming, does synthesizing mean the enzyme is bringing the free nucleotides into the order that the RNA polymerase is transcribing?

[shinny]

so essentially, RNA polymerase II just reads the bases while RNA polymerase I synthesizes the pre-mRNA?

Nono, he said rRNA as in ribosomal RNA. Basically, RNA polymerase I just makes the proteins sub-units that make up ribosomes. RNA polymerase II does all the stuff that's relevant to transcription.

[cipherpol]

Opps, misread that. Thanks again.

[TrueLight]

lol yeah

synthesizing, is just yeah making the mRNA ... yep catalyzing the reaction according to the base pair rule and then helps make the phosphodiester bond and then hydrogen bonding... and just bases are added at the 3' end the OH- group. and then makes the pre-mRNA 5'-3'.