The Biological Question Thread

[Russ]

stonecold's right, VCE is all about irritating details :S

Barr bodies require a bit of background to understand. They're a phenomenon that result from the process of X-inactivation. In humans, our sex chromosomes have two possible arrangements: XY or XX. Since an XX individual (woman) would have MORE X chromosomes than an XY individual (man), the hypothesis is that one of them is deactivated in order to prevent such an imbalance. The deactivated chromosome forms a "Barr body" and usually sits at the edge of the cell as a thick, dense bundle of chromatin. It has no actual biological "purpose" or function.

It's probably unnecessary for you to know the actual process by which it deactivates, but you should know that all but one X chromosome are deactivated. So if an individual had an aneuploidy (say XXXX), you'd expect three barr bodies to be present in all cells. What would you expect to observe in a man with Klinefelter's syndrome? Finally, the process of inactivation is random - during embryological development the chromosome to be deactivated is randomly selected in each cell, which leads to something called "atypical lyonisation". This means that women can be a chimaera of different alleles based on which ones are deactivated in which part of the body.

Random fact one: think about why almost all tortoiseshell cats are female...it's got to do with atypical lyonisation

Blebs in apoptosis: as the cytoskeleton of the cell is broken down, the integrity of the membrane is lost. As such, it can form random invaginations or bulges. This is the process of blebbing, since a bleb is a bulge that will eventually separate entirely from the cell to form an apoptotic body.

Random fact two: since UV light induces apoptosis, it increases the amount of apoptotic bodies in circulation. Since, Lupus patients have "anti nuclear antibodies", UV light exacerbates their condition by increasing the amount of nuclear material circulating through the body.



Sorry for all that, it's just that Xinactivation is probably my favourite thing in genetics and I went off on a bit of a tangent.

[sillysmile]

awesome explanations yet again... do you happen to be a biology teacher?
ty

[Russ]

No, but I wish I was. I'm just a student procrastinating over writing my lab report.

[sillysmile]

well, you certainly know your stuff! but maybe spend some more of that biological knowledge for your own best interests instead of other peoples.
okay question 1. : are short tandem repeats present in ribosomal RNA?
2. : what exactly are spacer regions and which types evolve the quickest?

[Russ]

I'm on break right now, I have spare time.

1. Don't actually know for sure, but if they're present in the DNA that codes for the rRNA then they'd be transcribed into the rRNA
2. Never heard of them evolving, but they sit between genes as a buffer and aid transcription

[sillysmile]

yeah, it's all good Russ
in regards to 2. yes apparently spacer regions are sequenced to compare different species, and different types of spacer regions have a quicker average rate of mutations (thus evolve quicker) but it's just a bit confusing

[simpak]

Are you just seeking this for your general knowledge because you totally don't need to know anything about whether ribosomal RNA has short tandem repeats.
I maintain that you need to know about parallel evolution though.

[sillysmile]

well, I guess it's partly for general knowledge, but it's actually because I was reading Edmunds notes and he mentioned something that sounded like short tandem repeats, and that it was a large component of rRNA. If I don't need to know that, then it's a benefit.
It's interesting that you mentioned parallel evolution, I gather you know that it's now out of the study design. Regardless I don't think parallel evo is too difficult to understand .

[Russ]

Most of rRNA is repeated/palindromic sequences (think about its tertiary structure), which might sound like STRs

[sillysmile]

are races and sub-species the same thing?

[Russ]

Not really. One of them (sub species) is part of taxonomical classification, whilst the other (race) isn't. Race is more of a social construct, biologically there's more difference "within" a race than between them.

You can use them synonymously without anyone caring, but technically they're probably different.

[jasoN-]

Describe the interrelationship between biological, cultural and technological evolution.
(technological ie. ART - eg. IVF)

[sillysmile]

well, I guess with the biological evolution of brain size and the muscles allowing speech, communication was possible. This ability to communicate allows the species to pass down information through the generations (e.g. burials) and gradually information is added/lost/altered, (this is cultural evolution). I'm not so sure about technological evolution but it's passed down tthrough generations, and woudln't be possible without the the intial biological evolution and also cultural evolution. Aight, so a lot of this was guesstimations, but it makes sense
If any details are incorrect, please feel free to correctify!

[Jdog]

ive got a question---

Im a bit confused about the classification of hominids /hominin since Nature of Biology seems different to VCAA, Is there a source where VCAA has updated the study design for this particular bit, cuz ive heard these classfications are ever changing due to constant discoveries/

[lexitu]

"When studying hominid evolution (eighth bullet point page 28 study design) students will encounter the term hominin and when answering relevant questions on Examination 2 will be expected to be familiar with and use both terms correctly as outlined below.

The taxonomic family Hominidae refers to the great apes (chimpanzees, gorillas and orangutans) and includes humans. Hominin refers to modern and extinct humans and their erect-walking ancestors including, for example, Australopithecus , Kenyanthropus and Homo genera. Under some older taxonomic classifications, hominin is used instead of hominid to refer to humans and humanlike ancestors and to describe the early humans now called Hominins. When the classification system changed to include apes in the human lineage (Hominidae), the term Hominid came to include apes and humans.

The term Hominin is used today, when talking about the human lineage and its ancestors. These changes in taxonomy have arisen from fossil, biochemical and genetic data. For further information: www.amonline.net.au/human_evolution/about.htm"

From VCAA.