VCE Biology Question Thread

[Rachelle]

can you tell from a pedigree if the parents are homozygous/heterozygous for a particular trait?

[ravi2]

can you tell from a pedigree if the parents are homozygous/heterozygous for a particular trait?

yes at times depending on the trait and offspring who have the trait - e.g. if the trait is recessive and the parents don't have the trait, and one offspring does, then the parent has to be a heterozygote for that particular trait.

[Stressedyear11here]

Pre mRNA has; methylated cap and poly A cap on the end and start of it, and I know that  RNA polymerase binds to the promotor of the gene and brings in the complementary bases to form pre mRNA.

What is it? Does it turn to mRNA/RNA ? Is it needed throughout the entire process of protein synthesis (included in transcription and translation)?

Many thanks

[grannysmith]

Yep, so RNA polymerase attaches to promoter region and unwinds and unzips the DNA strand, exposing the bases of the template strand. Complementary RNA nucleotides are added to the template strand by RNA pol, which grows into a single-stranded pre-mRNA molecule.

Pre-mRNA is just like an intermediary molecule (necessary). It becomes mature mRNA when introns are spliced, a methylated cap and poly-A tail is added.

[RazzMeTazz]

So just because a characteristic is controlled by polygenes it does not mean it has to show continuous variation?

It could show discontinuous variation as well, yes?

[Stressedyear11here]

Yep, so RNA polymerase attaches to promoter region and unwinds and unzips the DNA strand, exposing the bases of the template strand. Complementary RNA nucleotides are added to the template strand by RNA pol, which grows into a single-stranded pre-mRNA molecule.

Pre-mRNA is just like an intermediary molecule (necessary). It becomes mature mRNA when introns are spliced, a methylated cap and poly-A tail is added.

So, could we conclude that the poly-A tail and the methylated cap are like the 'hat and shoes' it puts on before it leaves the nucleus?

Thank you! Very helpful!! )

[grannysmith]

So, could we conclude that the poly-A tail and the methylated cap are like the 'hat and shoes' it puts on before it leaves the nucleus?

Thank you! Very helpful!! )

Yeah, I guess those are some differences between pre-mRNA and mRNA.

[nhmn0301]

So, could we conclude that the poly-A tail and the methylated cap are like the 'hat and shoes' it puts on before it leaves the nucleus?

Thank you! Very helpful!! )

Just adding up to what grannysmith has said:
Yes it can be quite useful to think of the methyl cap and poly A tail in that way but at the same time, you might be intestested to know more that the methyl cap is added to the 5' end and poly A tail is added to the 3' end. Methyl cap helps to stabilize the structure of mRNA and poly A tails help to prevent the RNA from getting any damages by the enzymes in the cytosol.

[Stressedyear11here]

Just adding up to what grannysmith has said:
Yes it can be quite useful to think of the methyl cap and poly A tail in that way but at the same time, you might be intestested to know more that the methyl cap is added to the 5' end and poly A tail is added to the 3' end. Methyl cap helps to stabilize the structure of mRNA and poly A tails help to prevent the RNA from getting any damages by the enzymes in the cytosol.

Awesome guys!! Thanks so much, guys!!!

[dankfrank420]

How do you determine the length of a DNA molecule from Gel Electrophoresis? If we have a clear scale at the side, why do we need a standard/control DNA lane?

[jessica666]

How do you determine the length of a DNA molecule from Gel Electrophoresis? If we have a clear scale at the side, why do we need a standard/control DNA lane?

I think you need a standard with fragments of known sizes because agarose gels can differ slightly

[dankfrank420]

Why do some bacteria take up plasmids and transform while others do not?

[Scooby]

Why do some bacteria take up plasmids and transform while others do not?

The bacteria need to be made competent to take up the plasmids (eg. with heat therapy). If this doesn't happen for a particular bacterial cell, it won't take up the plasmid

How do you determine the length of a DNA molecule from Gel Electrophoresis? If we have a clear scale at the side, why do we need a standard/control DNA lane?

Load DNA fragments of known length into one of the wells as a control. That way you known which DNA fragments make up each of the bands produced

I think you need a standard with fragments of known sizes because agarose gels can differ slightly

And we might not always let the fragments run for the same amount of time

[DJA]

At what stage of Meiosis does Crossing Over or synapsis occur when genes have the possibility of swapping between homologous chromosomes?

[grannysmith]

At what stage of Meiosis does Crossing Over or synapsis occur when genes have the possibility of swapping between homologous chromosomes?

Prophase I