VCE Biology Question Thread

[Biology24123]

Do the MHC actually get recognised as self or non self? Don't they just present antigens

[vox nihili]

Aspiringdoc is right - G0 is definitely not the name of the checkpoint, rather the 'resting' phase where cells aren't dividing or preparing to divide.  I think when cells 'fail' the checkpoint, they probably go to apoptosis rather than into G0, but my knowledge is shaky here

Just going to clarify G0. There are plenty of cells in the human body that don't divide. These cells are said to have entered a state of senescence, which in the context of the cell cycle is represented by G0.

It is possible for a cell to exit G0 and then proceed through the cell cycle; however, a cell in G0 is most certainly not preparing to divide.

If a cell fails the checkpoint, a number of things can happen. Typically, various enzymes will try to correct whatever has caused the cell to fail. If they can't do that, the cell will normally undergo apoptosis. It can, however, go into G0 instead.

Do the MHC actually get recognised as self or non self? Don't they just present antigens

They do present antigens. To activate a T-cell, however, it must bind to the MHC molecule AND the antigen simultaneously.

[Biology24123]

Does recognition of a non self antigen on a MHC 1 cause memory cells to from or just the destruction of the cell

[StupidProdigy]

Alright, back to AOS 1.. How do plasmids become cut open by restriction enzymes? because doesn't bacterial dna have methyl caps on it to stop its own restriction enzymes damaging it whilst fighting against viruses and the like? I'm guessing that you use restriction enzymes from other bacteria that are not naturally present in the bacterium of interest to cut open plasmid, since the plasmid would be resistant to its own restriction enzymes yeah? Thankyou

Anyyyyoneee care to hazard a guess??

Is there short tandem repeats in pseudogenes since pseudogenes are considered junk dna? Tiny bit out of the course I think but I'm interested aha

[vox nihili]

Alright, back to AOS 1.. How do plasmids become cut open by restriction enzymes? because doesn't bacterial dna have methyl caps on it to stop its own restriction enzymes damaging it whilst fighting against viruses and the like? I'm guessing that you use restriction enzymes from other bacteria that are not naturally present in the bacterium of interest to cut open plasmid, since the plasmid would be resistant to its own restriction enzymes yeah? Thankyou

You can treat plasmids with enzymes that break off the methyl groups. There are also restriction enzymes that are selective for methylated DNA. For instance, we've been working with DpnI this week, which can only cut DNA when it's methylated.

Anyyyyoneee care to hazard a guess??

Is there short tandem repeats in pseudogenes since pseudogenes are considered junk dna? Tiny bit out of the course I think but I'm interested aha

Yes, they could occur therein but they would less frequently. Genes tend not to have many STRs, if any, and pseudogenes are, by their very nature, similar to normal genes. However, it is possible.

[StupidProdigy]

Do we need to know about all the homo species? Would it be safe to mainly focus on homo sapiens? thankya

[vox nihili]

Do we need to know about all the homo species? Would it be safe to mainly focus on homo sapiens? thankya

Know the trends in human evolution and what drove those trends. Knowing the individual species doesn't really tell my much

[cosine]

When a phenotype is 100% for a certain triat, how can you write the phenotypic ratio? Say there are 4 offspring with red hair and none with another colour, would you write 4Red:0Nonred or just 1Red:0Nonred?

Also, (dihybrid) a question says that two mice are heterozygous but are pure breeding, how can this be? I thought that if an individual was pure breeding, then it was homozygous for the trait?

[sunshine98]

When a phenotype is 100% for a certain triat, how can you write the phenotypic ratio? Say there are 4 offspring with red hair and none with another colour, would you write 4Red:0Nonred or just 1Red:0Nonred?

Also, (dihybrid) a question says that two mice are heterozygous but are pure breeding, how can this be? I thought that if an individual was pure breeding, then it was homozygous for the trait?

1. 4:0
2. certainly a mistake , or it probably meant that it was a heterozygous mouse from pure breeding parents. But you are right , pure breeding is homozygous for trait. 

[StupidProdigy]

DNA helicase isn't used in transcription right? My understanding is that RNA polymerase can 'unwind' the dna sequence without the presence of helicase, is this accurate? Thanks guys

anddd are the terms degeneracy and redundancy synonymous for vce bio?

[TheAspiringDoc]

DNA helicase isn't used in transcription right? My understanding is that RNA polymerase can 'unwind' the dna sequence without the presence of helicase, is this accurate? Thanks guys

Please correct me if I'm wrong, but my understanding is that DNA helicase is used in transcription (that is, breaking DNA into RNA). I don't have a very good understanding of all of this, but if you type "DNA polymerase" into google images, you may find the second top result of some interest.
Doubt this helped, but hope it did

[vox nihili]

DNA helicase isn't used in transcription right? My understanding is that RNA polymerase can 'unwind' the dna sequence without the presence of helicase, is this accurate? Thanks guys

anddd are the terms degeneracy and redundancy synonymous for vce bio?

DNA helicase is used in transcription.

[HighTide]

Please correct me if I'm wrong, but my understanding is that DNA helicase is used in transcription (that is, breaking DNA into RNA). I don't have a very good understanding of all of this, but if you type "DNA polymerase" into google images, you may find the second top result of some interest.
Doubt this helped, but hope it did

Sup,
Hope you don't mind me just pointing out that DNA helicase is involved in DNA replication - not transcription. It's responsible for separating the two strands and creating the replication fork. In transcription,  RNA polymerase is the main enzyme. Also, DNA isn't broken into RNA, it's transcribed.

DNA helicase isn't used in transcription right? My understanding is that RNA polymerase can 'unwind' the dna sequence without the presence of helicase, is this accurate? Thanks guys

anddd are the terms degeneracy and redundancy synonymous for vce bio?

In transcription, RNA polymerase can indeed unwind the DNA. In DNA replication its helicase, in transcription its RNA polymerase.
Yes, the two terms are but I think you can refer to it as the "redundant and degenerate nature of the genetic code" etc.

When a phenotype is 100% for a certain triat, how can you write the phenotypic ratio? Say there are 4 offspring with red hair and none with another colour, would you write 4Red:0Nonred or just 1Red:0Nonred?

Also, (dihybrid) a question says that two mice are heterozygous but are pure breeding, how can this be? I thought that if an individual was pure breeding, then it was homozygous for the trait?

Perhaps the question was referring to mating of a pure breeding dominant AABB vs a pure breeding recessive aabb. In that case, the offspring would be heterozygous. In other cases Sunshine would obviously be correct!

[warya]

Could someone please explain independent assortment to me I'm really having trouble understanding it

[pi]

transcription (that is, breaking DNA into RNA)

Other errors have been pointed out, but a "breaking" a double strand of DNA into a single strand of DNA is not equivalent to being RNA You may want to read up on what transcription actually is and how it works.