VCE Biology Question Thread

[Biology24123]

Out of study design this or?

No just extra knowledge

[BakedDwarf]

Attached is the question, indeed the next part talks about DNA, but honestly is this ambiguous or not because I really have a problem here because I always lose marks because of trying to be specific, like I knew exactly what a DNA probe is, single stranded DNA molecule that binds to the complementary DNA strand to mark it so it can be monitored, but I purposely did not write that because the question did not ask for the definition of DNA probe, but simply just probe. Honestly, what should I do to avoid stuff like this? Really disheartening knowing I am susceptible to easy marks like this

Can a probe be anything else other than DNA?

[BakedDwarf]

What do we actually need to know about the types of absolute dating techniques? What types of questions would be asked in a VCAA exam about it?

I found this information somewhere (don't remember where, but it's not mine) and i'm just wondering if it's correct, and if it's sufficient for VCE:
- Carbon-14 dating is a radiometric method that measures the ratio of C-14 to C-12 in a sample of organic material to estimate the time since the death of the organism (C-14 decays to N-14 when the organism dies, but its C-12 stable isotope remains constant)
- Potassium-argon dating (K-Ar) dating is a technique useful for dating igneous rocks over a wide age range and based on the radioactive decay of a potassium isotope to argon; the older the rock, the longer for potassium-40 to decay and for argon-40 to accumulate
- Electron-spin resonance (ESR) is technique useful for dating objects buried 50,000 to 500,000 years ago because when objects are buried they are bombard by natural radiation from the soil, which causes some of the electrons in the minerals to move to a higher energy state and become trapped; that is, the longer the material has been buried, the greater the accumulation of high energy electrons

Is there anything else I need to know about absolute dating?

[jyodesh.com]

Can a probe be anything else other than DNA?

I'm prettty sure there are RNA probes. I think a good answer would be "A probe is a fluorescently or radioactively labelled single stranded nucleic acid molecule with a complementary sequence to the nucleic acid sequence investigated"

[cosine]

I'm prettty sure there are RNA probes. I think a good answer would be "A probe is a fluorescently or radioactively labelled single stranded nucleic acid molecule with a complementary sequence to the nucleic acid sequence investigated"

Thanks man

So probes are ONLY nucleic acid? I thought other molecules, for example a drug, which can label certain molecules in an organism?

[jyodesh.com]

Thanks man

So probes are ONLY nucleic acid? I thought other molecules, for example a drug, which can label certain molecules in an organism?

There are fluoresecntly/radioactively labelled small molecules and antibodies but I've usually encountered the word "probe" in the context of nucleic acid and "fluorescent antibody" in the context of antibodies.

[cosine]

There are fluoresecntly/radioactively labelled small molecules and antibodies but I've usually encountered the word "probe" in the context of nucleic acid and "fluorescent antibody" in the context of antibodies.

So then why did you write before that a probe was a single stranded nucleic acid? o.O

[jyodesh.com]

So then why did you write before that a probe was a single stranded nucleic acid? o.O

If I saw someone talking about a probe I would assume their talking about a DNA or RNA probe, if they say probe but their talking about a fluorescent antibody for detecting proteins then I'd say they're using it innappropriately because they can just say "fluorescently labelled antibody" and not confuse anyone BUT I would understand that there may be some denotative ambiguity.
It's a sorta context dependent thing like if you asked a lay person they'd think a probe is something that aliens stick up your butt. In the context of biology though probe usually refers to a nucleic acid probe

[vox nihili]

If I saw someone talking about a probe I would assume their talking about a DNA or RNA probe, if they say probe but their talking about a fluorescent antibody for detecting proteins then I'd say they're using it innappropriately because they can just say "fluorescently labelled antibody" and not confuse anyone BUT I would understand that there may be some denotative ambiguity.
It's a sorta context dependent thing like if you asked a lay person they'd think a probe is something that aliens stick up your butt. In the context of biology though probe usually refers to a nucleic acid probe

That's reasonable, I reckon that's the way to go.

RNA probes are rare. They're too difficult to work with, but they do still exist.

[mahler004]

It's all semantics and context-dependent. 'Probe' can mean a lot of things. I'd refer to a fluorescent labelled antibody as a 'florescent probe.' They don't even need to be fluorescent/radioactive - a probe is simply something you use to detect something else.

[cosine]

Thanks guys, got it, if there's context to a question, I should relate the answer to it

1. I was able to cancel out the other options and got C, but I wasn't entirely sure about it because apart from the circular single chromosome, don't bacteria have plasmids that could possess regulatory and structural genes too?

2. Why is the answer not D for question 12?

3. If these are the chromosomes belonging to a homologous pair, then does that not mean the egg would have exactly the same (only one of though) of these chromosomes? Why is it that the answers have all different alleles?

4. I don't understand how the answer is not C. Doesn't meiosis in females result in four haploid cells per germline cell?

[sunshine98]

3. If these are the chromosomes belonging to a homologous pair, then does that not mean the egg would have exactly the same (only one of though) of these chromosomes? Why is it that the answers have all different alleles?

4. I don't understand how the answer is not C. Doesn't meiosis in females result in four haploid cells per germline cell?

3- crossing over. is the answer c?
4- in females 3 of the eggs degenerate and are called polar bodies . Only 1 of the daughter cells are functional .

[cosine]

4- in females 3 of the eggs degenerate and are called polar bodies . Only 1 of the daughter cells are functional .

Oh come on, what even is this...? Is this in the study design or not? If this is true then is it not wrong to say that meiosis results in the production of 4 gametes from germline cells?

[cosine]

If homologous chromosomes cross over, then why doesnt crossing over occur in mitosis? Don't the homologous chromosomes also line up in the middle of the cell during mitosis too?

[Mishmosh]

Could someone summarise DNA sequencing for me?

If homologous chromosomes cross over, then why doesnt crossing over occur in mitosis? Don't the homologous chromosomes also line up in the middle of the cell during mitosis too?

Dont sister chromatids line up in mitosis therefore it would be the same genes, while in meiosis it's homologous chromosomes (different genes)?