VCE Biology Question Thread

[jessica666]

What is the difference between DNA 'passenger fragments' and 'genes of interest'

[dankfrank420]

Hey guys I have my Meiosis & Inheritance SAC tommorow, which will contribute 25 marks out of 100 for my GA2 score. Could someone provide some model answers to questions (I suspect) that will be on the SAC?

A dihybrid cross between two heterozygous alleles is expected to produce a 9:3:3:1 ratio. However, you would have observed something different. Account for this difference in offspring phenotype, assuming the genes are unlinked

Meiosis produces genetic variation in their offspring in a number of ways. Name the processes and stages that they occur in.

[ravi2]

Meiosis produces genetic variation in their offspring in a number of ways. Name the processes and stages that they occur in.
[/quote]

Meiosis can produce genetic variation in offspring through the crossing over of homologous chromosomes of certain alleles within the same gene loci during prometaphase 1. (what i think, someone correct me if wrong  please.) Also, meiosis can cause genetic variation through the random assortment of homologous chromosomes along the equitorial plane during metaphase 1 - this gives 2^23 possibilities. Mutations in meiosis, such as non-disjunction during anaphase 1 and anaphase 2could lead to genetic variation as well. Errors in DNA replication during the synthesis stage of interphase can also cause genetic variation. Finally, since millions of gametes are produced, any one sperm can go and fuse with any egg at random, so this further leads to genetic variation. This occurs during fertilisation.

[dankfrank420]

Thanks Ravi.

Also, can recombiant offspring be produced if no crossing-over has occurred? For example the 3:3: 1 in the 9:3:3:1 ratio are all different to their parents, even though recombination has not occurred.

[ravi2]

I am pretty sure not... but do not sure if this is the right answer
The reason why they are different to their parents even though recombination has not occured, the inheritance of this trait involves two unlinked gene loci, so according to a dihibrid cross, offspring different to the parent can be produced.
Probably not the best answer

[katiesaliba]

Are DNA probes used in DNA profiling simply to allow the bands to fluoresce under UV light? Thanks

[nerdmmb]

Are DNA probes used in DNA profiling simply to allow the bands to fluoresce under UV light? Thanks

In most techniques, it is also used to hybridise with a particular DNA fragment in order to extract it.
This may include techniques such as gene cloning and PCR

[ravi2]

I know this question has been asked many times but sorry for asking again
Do you think it is smart to make notes for biology now? And if so how long should you spend on them?
Or is it too late and it is more smart to practice questions instead?
thanks:D

[Reus]

I know this question has been asked many times but sorry for asking again
Do you think it is smart to make notes for biology now? And if so how long should you spend on them?
Or is it too late and it is more smart to practice questions instead?
thanks:D

I'd suggest doing notes, I've being doing mine since the start of the year. Unit 3 notes complete, however my Unit 4 notes are quite behind as compared to what my school is up to but meh. It's never too late!

[RazzMeTazz]

I don't understand what is meant by parental gametes and recombinant gametes ?
And how does the map units of the distance between two linked genes allow to determine the percentage of recombinant gametes??

[nerdmmb]

I don't understand what is meant by parental gametes and recombinant gametes ?
And how does the map units of the distance between two linked genes allow to determine the percentage of recombinant gametes??

Parental gametes are those whose genetic material is identical to the parent's genetic material (DNA).
On the other hand, recombinant gametes are those whose DNA is not identical to the parent's DNA as recombination has occurred between the chromosomes.

[Reus]

Anyone done a inheritance/probability prac sac??

[katiesaliba]

Does annealing concern the formation of hydrogen bonds between base pairs only? Is hybridisation therefore synonymous for the verb annealing?

[Reus]

Does annealing concern the formation of hydrogen bonds between base pairs only? Is hybridisation therefore synonymous for the verb annealing?

I think annealing is the sub-process whereas hybridisation is more general to describe the formation of a hybrid. I would say annealing also occurs in hybridisation (the joining of complementary nucleotides) so in a sense they are synonymous.

Note: Don't take my 100% word for it, this is just what I think.

[jessica666]

To make multiple copies of a gene, when is bacterial gene cloning used, and when is PCR used?