The Biological Question Thread

[sillysmile]

okay hang on, this child could be IA and i right?
so the man could be the father. my bad.

[sillysmile]

In regards to this question from insight 2010

In the wild, the likelihood of producing a white, crossed-eyed Bengal tiger is 1 in every 10,000, an approximation based on documented observations of white cubs in their natural habitat. There are very few adult white tigers in the wild. When bred in captivity, mortality rates of cubs are in excess of 80%. The recessive allele that produces white, cross eyed tigers is also linked with other, often fatal characteristics including immune deficiency, scoliosis (curvature) of the spine, cleft palates and early death.
1d. i. What is the name of the event that has produced the recessive allele in the Bengal tiger?


1 mark
Solution
Deleterious mutation.

^what is a deleterious mutation... I just wrote gene mutation.
is this just a deletion mutation? and how could that be inferred?

[akira88]

In regards to this question from insight 2010

In the wild, the likelihood of producing a white, crossed-eyed Bengal tiger is 1 in every 10,000, an approximation based on documented observations of white cubs in their natural habitat. There are very few adult white tigers in the wild. When bred in captivity, mortality rates of cubs are in excess of 80%. The recessive allele that produces white, cross eyed tigers is also linked with other, often fatal characteristics including immune deficiency, scoliosis (curvature) of the spine, cleft palates and early death.
1d. i. What is the name of the event that has produced the recessive allele in the Bengal tiger?


1 mark
Solution
Deleterious mutation.

^what is a deleterious mutation... I just wrote gene mutation.
is this just a deletion mutation? and how could that be inferred?

del·e·te·ri·ous/ˌdeliˈti(ə)rēəs/
Adjective: Causing harm or damage
It's just a word describing that the mutation is fatal. Nothing to do with deletion If I had done that question I would have just wrote mutation, but I wouldn't know if the "deleterious" is necessary for getting a mark. Probably ask a teacher.

[Russ]

Deleterious mutations aren't necessary fatal, they just reduce the relative fitness of the organism. Most are probably just early stop codons (nonsense mutations).

An example might be SCA in humans (not nonsense though) which is deleterious but not fatal. As you've probably been told over and over again, it actually protects you from malaria.

Requiring "deleterious mutation" is a pretty harsh marking scheme, personally I would have written just "mutation"

[simpak]

Mutation should be good enough.

[Allygator]

Hi
Can anyone tell me what we need to know about apoptosis?
Thanks in advance!

[Russ]

In general:

Know a VCAA approved definition of what it is and why it occurs. Can it occur without external stimuli etc. Be able to give a rough sequence of events. Be able to differentiate between apoptosis and necrosis.

If you want extra credit, know the p53 gene

[stonecold]

Yeah, p53 gene and tumor suppressing gene are involved.  Cell shrinks, nucleus breaks down, organelles recycled, dead cell fragments engulfed by phagocytes.

[golden]

What is the difference between a hypervariable region and a short tandem repeat?
Also, with gene therapy, the effects are sometimes short lived - is this because the cells usually die before it has a chance to undergo cell division to produce another cell with the gene?

Thanks.

[Russ]

mmm fine distinction, i had to go find my biology dictionary.

i get the feeling than an HVR is much more variable than an STR. so whilst we have a library of STR sequences that we can match individuals to, an HVR could conceivably be different across the entire population

For gene therapy, that's one of the reasons but the crux is just that the procedure is still being refined empirically. In other words, nobody reaaally knows what they're doing and every time they make a mistake they change something to fix it. So until we have solutions to problems like immune response/stability/vectors etc. it's very hard to get a long term response

[golden]

I see, so if there was a question on the exam that stated for example:
What is the difference between a short tandem repeat and a hypervariable region, and or:
Why are the effects of gene therapy sometimes short lived?

What is the best way to answer these questions?

[matt123]

im just posting so it goes into the " show new replies" lol
i wanna know the answer to your questions
they are good ones.

lol sorry i cant help.. got no clue

[golden]

Wikipedia defines it as:

Short tandem repeat:
A short tandem repeat (STR) in DNA occurs when a pattern of two or more nucleotides are repeated and the repeated sequences are directly adjacent to each other. The pattern can range in length from 2 to 50 base pairs (bp) (for example (CATG)n in a genomic region) and is typically in the non-coding intron region. A short tandem repeat polymorphism  (STRP) occurs when homologous STR loci differ in the number of repeats between individuals. By identifying repeats of a specific sequence at specific locations in the genome, it is possible to create a genetic profile of an individual.

Hypervariable region:
A hypervariable region (HVR) is a location within nuclear DNA or the D-loop of mitochondrial DNA in which base pairs of nucleotides repeat (in the case of nuclear DNA) or have substitutions (in the case of mitochondrial DNA). Changes or repeats in the hypervariable region are highly polymorphic.


Here we are comparing: 'A short tandem repeat (STR) in DNA occurs when a pattern of two or more nucleotides are repeated...' with '...in which base pairs of nucleotides repeat (in the case of nuclear DNA) or have substitutions (in the case of mitochondrial DNA)...'

Can you distinguish the differences between this information provided?

[golden]

Nature of Biology Third Edition Book 2 defines it as:

Short tandem repeats (STRs): Chromosomal sites where many copies of short DNA sequence are joined end to end; also termed microsatellites. Sequences are normally 2 to 4 base pairs, and the number of repeats are very variable between unrelated people.

Hypervariable regions (HVRs): Regions on chromosomal DNA in which great variation exists in unrelated individuals, often as a result of variation in the number of repeats in short base sequences.

[golden]

Nature of Biology Third Edition Book 2 states:
Hypervariable regions of DNA that are currently used for identification are:
Short tandem repeats in nuclear DNA...
Hypervariable regions in mtDNA...

Would that mean that short tandem repeats are hypervariable regions? But if that was the case, then why categorize it in this way?