VCE Biology Question Thread

[Gogo14]

Hey guys I'm struggling to think of what to discuss in the conclusion of the prac report of our genetic SAC.

We crossed some fruit flies , observing a trait controlled by a single gene loci with 2 alleles and observed the results over several generations.

Could someone help me think of what to talk about? PELISSE MY SACS TOMMOROW

Hvnt done much of that at school, so cant help you there. But you can structure your conclusion by:

Was the hypothesis supported?
Was the aim found?
If so, what does the results tell you?

Soz if its not helpful, can only give general advice here

[Gogo14]

Got some questions of my own with my response
1. "Alleles of closely linked genes are more likely to be inherited together than alleles of widely separated genes. Why?"
- Alleles are close together, hence have a higher probability of being inherited together in mitosis/ meiosis? Actually have no clue
2. "Genes were isolated from a cat, cyanobacteria and a cauliflower, what are the similarities and differences?"
- not really sure what this question is asking or the level of specificity required.
3. "If a sequence of DNA was take from a monkey, would the same DnA in a flower translate in a different way?
- Probably not. The monkey is a different organism to a flower, and hence have the chance of the same gene coding for different proteins depending on the organism it is in. Not sure how to word this one.
4. "4 black cats resulting from a cross from a black cat( unknown genotype) and a grey cat(dd) would prove that the black cat is DD. Black is dominant.
- it would not prove that the cat is DD because the cat could also be Dd but just not given birth to a grey cat yet. However, it does give the DD genotype a higher probability of being true.
5. We did gel electrophoresis last week with DNA fragments cut up by restriction enzymes. However, in the negative control (no enzymes) there were 2 fragment readings, each with a different number of base pairs. HOW CAN THERE BE 2 PIECES WHEN THE DNA HASNT EVEN BEEN CUT.

Thanks in advance!

[anotherworld2b]

I was wondering if i get help on understanding how menstruation and ovulation occurs every 28 days but each happens every 14 days?

[Calebark]

I was wondering if i get help on understanding how menstruation and ovulation occurs every 28 days but each happens every 14 days?

Hi - I think this would be a better question for the HHD question thread, as I don't remember doing this in Biology. If I'm remembering correctly, it's the menstrual cycle which is every 28 days. Menstruation and ovulation are stages of the cycle.

Rather than learning a bit more about it and explaining myself as I'd do a poor job (although perhaps someone here can help), I'll link you to this, this, and this. Hopefully these should cover anything you wish to know. Good luck

[HasibA]

what is the purpose of using long primers? what would be the problem using very short primers (eg 5 bases long)? ty
name a technique that would allow you to determine if two fragments are indetical? i think DNA sequencing, but didnt explain it well.

got these q's a bit wrong my sac- help would be nice.

[vox nihili]

I was wondering if i get help on understanding how menstruation and ovulation occurs every 28 days but each happens every 14 days?

The menstrual cycle isn't part of the VCE course.

If it's part of HSC, you can try the following thread:

Biology Question Thread

If it's not an HSC question, you can try our "beyond VCE" thread:

Biology: Beyond VCE question thread (for questions outside the course)


I'm happy and able to answer your question, but I want to ensure that this thread stays on topic.
Contrary to Calebark's suggestion, I don't think HHD is the right place for your question sorry! Calebark pretty much answered your question though, it must be said. But if you want more detail, that's where to go

what is the purpose of using long primers? what would be the problem using very short primers (eg 5 bases long)? ty
name a technique that would allow you to determine if two fragments are indetical? i think DNA sequencing, but didnt explain it well.

got these q's a bit wrong my sac- help would be nice.

There are four different bases. That means that there are 1024 different 5 base combinations. The genome is about 3 billion bases. That means that each of the 1024 five base combinations occurs about two and a half million times in the genome. If you want to target a particular gene, you have to go bigger than five bases, because otherwise you'll expand the region you're looking for, along with 2.5 million others!

DNA sequencing could work. Also a restriction digest then gel electrophoresis

[HasibA]

DNA sequencing could work. Also a restriction digest then gel electrophoresis

Could you explain 'restriction digest' a bit more? haven't really heard of the term (unless it's another name for something else)
edit: should i know what a chaisma/chiasmata is for mitosis etc.? do i have to know about down syndrome for the exam?? how much should i know about apoptosis ? ty

[vox nihili]

Could you explain 'restriction digest' a bit more? haven't really heard of the term (unless it's another name for something else)
edit: should i know what a chaisma/chiasmata is for mitosis etc.? do i have to know about down syndrome for the exam?? how much should i know about apoptosis ? ty

Does anyone currently doing VCE want to have a crack at explaining how restriction enzymes work? I'm more than happy to, but I thought I'd give you guys a chance to practise and then I'll clarify any areas of weakness

Nope, don't need to know about chiasmata. It's just the site of crossing-over/recombination.
Down syndrome probably not, but understanding the principles would be good.
Just appreciate that apoptosis is a deliberate, programmed cell death that can be triggered by internal events or external events. Anything they ask on apoptosis is usually pretty straightforward.

[HasibA]

<snip>

thanks!

[Calebark]

Does anyone currently doing VCE want to have a crack at explaining how restriction enzymes work? I'm more than happy to, but I thought I'd give you guys a chance to practise and then I'll clarify any areas of weakness

I'm not too sure with this as well, so giving it a go may help me, haha.

Enzymes have a specific shape, and act on specifically shaped substrates. So, in order to find what it must act on, the substrate would travel down the DNA strand until it finds the shape specific to it (which is 4-8 nucleobases long?), where it will then activate. Would this be correct?

[vox nihili]

I'm not too sure with this as well, so giving it a go may help me, haha.

Enzymes have a specific shape, and act on specifically shaped substrates. So, in order to find what it must act on, the substrate would travel down the DNA strand until it finds the shape specific to it (which is 4-8 nucleobases long?), where it will then activate. Would this be correct?

It sounds like you're onto something here, but we need more info. What do restriction enzymes actually do?


I feel like you know it, but just haven't explicitly stated it. Remember you're trying to explain this to someone who hasn't heard of restriction enzymes!

[plsbegentle]

They are enzymes that cut a strand of DNA into fragments. Restriction enzymes can only cut at certain regions of a sequence producing either 'sticky' of 'blunt' ends. Blunt ends are produced when the enzyme cuts directly at the same point in the sequence.
For example,
ACG|GCA
TGC|CGT
While sticky ends are produced when the enzyme cuts at a different point,
For example:
A|CGGCA
TGCCG|T

[vox nihili]

They are enzymes that cut a strand of DNA into fragments. Restriction enzymes can only cut at certain regions of a sequence producing either 'sticky' of 'blunt' ends. Blunt ends are produced when the enzyme cuts directly at the same point in the sequence.
For example,
ACG|GCA
TGC|CGT
While sticky ends are produced when the enzyme cuts at a different point,
For example:
A|CGGCA
TGCCG|T

What do we think everybody, is he right?

[Calebark]

Ahh, I shall try again

Restriction enzymes are enzymes used to cut out parts of DNA. They do this by cutting at unique nucleic acid sequences called 'recognition sites'. As enzymes have specific shapes in order to act on specific substrates, the enzyme will travel down the DNA strand until it finds the shape specific to the enzyme - in other words, the recognition site. The enzyme will then cleave through the sugar-phosphate backbone ( I admit, I don't know exactly how this works ). The restriction enzyme will leave two types of ends on the helix, being blunt ends and sticky ends, with blunt ends leaving no nucleobases overhanging, and sticky ends leaving nucleobases overhanging.

EDIT: Yes, I think Plsbegentle's explanation was correct and concise (always good to see!)

[solution]

What does the circle with the dot mean?