Psyxwar's Biology 3/4 Question Thread

[Yacoubb]

mtDNA is useful because of its low mutation rate. I'm not really au fait with all of it, but that's definitely an important statement to make. mtDNA has been used to track really long lineages back to the first humans.

But the HPV D-loop has a high mutation rate? Its just a hypervariable region (non-coding).. Is what I said wrong?

[vox nihili]

But the HPV D-loop has a high mutation rate? Its just a hypervariable region (non-coding).. Is what I said wrong?

It's probably not, though I wouldn't talk about that. The idea is that the genes in the mtDNA barely mutate.

[sparked]

To answer the mitochondria usefulness question:

1) mitochondria are an inherent part of the eukaryotic cell since its conception, meaning all comes animals are in theory, descended from the same mitochondrial cell. The mutational difference between the MAJORITY of genetic information in the mitochondria is extremely limited, allowing us to compare segments between species to determine their genetic relatedness.

2) the cytochrome c gene region is highly preserved amongst all species of animals because of its importance in the electron transport chain which is critical to life. Small single base pair mutations may occur but to a limited extent and therefore is an accurate measure of relaxedness.

[vox nihili]

To answer the mitochondria usefulness question:

1) mitochondria are an inherent part of the eukaryotic cell since its conception, meaning all comes animals are in theory, descended from the same mitochondrial cell. The mutational difference between the MAJORITY of genetic information in the mitochondria is extremely limited, allowing us to compare segments between species to determine their genetic relatedness.

2) the cytochrome c gene region is highly preserved amongst all species of animals because of its importance in the electron transport chain which is critical to life. Small single base pair mutations may occur but to a limited extent and therefore is an accurate measure of relaxedness.

It is really important to drive home the fact that it's maternally inherited as well though. It gives a direct lineage, which nuclear DNA just doesn't give.

[LazyZombie]

Question from the OP;

Do females have a non-homologous pair of sex chromosomes? Apparently due to X-inactivation (and the formation of a Barr body), the X chromosomes are not considered homologous.

[pi]

Question from the OP;

Do females have a non-homologous pair of sex chromosomes? Apparently due to X-inactivation (and the formation of a Barr body), the X chromosomes are not considered homologous.

Why did he ask me to ban him... -_______________-

[Yacoubb]

Question from the OP;

Do females have a non-homologous pair of sex chromosomes? Apparently due to X-inactivation (and the formation of a Barr body), the X chromosomes are not considered homologous.

Homologous chromosomes are paired chromosomes of the same size that carry the same gene loci. Because females have two X-chromosomes of the same size, and both carry the same gene loci (even though one X-chromosome is inactivated), they could technically still be considered homologous.

[vox nihili]

Homologous chromosomes are paired chromosomes of the same size that carry the same gene loci. Because females have two X-chromosomes of the same size, and both carry the same gene loci (even though one X-chromosome is inactivated), they could technically still be considered homologous.

Even the X and Y are homologous to some extent. They behave as homologous chromosomes during meiosis I. They can actually synapse in a region on each chromosome called the pseudoautosomal region. Obviously beyond the VCE course, but it's kind of cool nonetheless.

[Stick]

^ I did a VCAA exam recently and the X and Y chromosomes were considered to be homologous.

[vox nihili]

^ I did a VCAA exam recently and the X and Y chromosomes were considered to be homologous.

Realistically, if that's the method by which meiosis occurs in humans (there are other methods), then they kind of have to be, otherwise you'd get a huge number of aneuploids.

[hardworker]

I just wanted to ask if Bacteria are hetrotrophic and not autotrohpic. And why is reverse transcriptase used has an enzyme in order for a retrovirus to be a successful vector?

[Yacoubb]

I just wanted to ask if Bacteria are hetrotrophic and not autotrohpic. And why is reverse transcriptase used has an enzyme in order for a retrovirus to be a successful vector?

Some bacteria are heterotrophic, whilst other bacteria are autotrophic. E.g. cyanobacteria.

Reverse transcriptase is an enzyme used to synthesise DNA from an RNA template. Before being able to integrate the genetic material of the retrovirus (what we call viruses that have a core RNA genome) into the host cell, it must be converted to DNA. When it is converted, the host cell begins to express the genes, which code for proteins that create viral components necessary to build up the viral particles (biosynthesis is said to occur).

Now, in terms of genetic engineering, reverse transcriptase must be used so that when you need to transfect a cell (you typically use retroviruses for inserting foreign DNA into eukaryotic cells - hence, transfection), DNA as opposed to RNA is inserted into the cell. Its the same as what would occur if the retrovirus were a pathogen, except of course the retrovirus has lost its virulence when being used in genetic engineering.

Hope this helped.

[LazyZombie]

"Which cells in the body of the bull were affected by the mutation to allow HERDA to be inherited?"

Answers say gametes or sperm; would gonads also be correct? This is a VCAA question so I wasn't sure (even though gonad seems to be a better answer as it refers to body cells?)

[Yacoubb]

"Which cells in the body of the bull were affected by the mutation to allow HERDA to be inherited?"

Answers say gametes or sperm; would gonads also be correct? This is a VCAA question so I wasn't sure (even though gonad seems to be a better answer as it refers to body cells?)

The only cells that cross the generation gap are gametes. Because the question specifically asks what cells would allow it to be inherited, the mutation would need to affect sperm. Gonads would not be correct.

[slothpomba]

"Which cells in the body of the bull were affected by the mutation to allow HERDA to be inherited?"

Answers say gametes or sperm; would gonads also be correct? This is a VCAA question so I wasn't sure (even though gonad seems to be a better answer as it refers to body cells?)

Gonads are the actual reproductive organs themselves. The skin, muscle, tissue etc that comprise them wont be passed inherited in the same way your kids wont inherit your haircut or your nail polish. The ONLY cells in which changes can be passed down and inherited through are the germ cells (sperm and eggs).

If it doesn't affect those, then it wont be passed down.