VCE Biology Question Thread

[Biology24123]

Can someone please summarise human impact on evolution including the techniques (e.g artificial selection)
That would be great. Thanks

[grindr]

So, the offspring are SsWw - as the SW came from one parent, and the sw from another, these offspring have SW on one chromosome and sw on the other.  So, unless crossing over occurs between gene 1 and gene 2, then offspring of the test cross (SsWw x ssww) will be passed either SW or sw - they'll only get sW or Sw if crossing over happens, which is unlikely as these genes are close together.  So there'll be lots of SW or sw (long and straight/short and wavy), but very few sW or Sw (long and wavy, short and straight), so approx equal SW and sw --> D.

Ah, this makes more sense. Thanks Bangali_lok!

[Sine]

Can someone please summarise human impact on evolution including the techniques (e.g artificial selection)
That would be great. Thanks

So human impact on evolution is quite easy to understand if you understand the means of natural selection.

Selective breeding: Humans act as the selective agent, choose organisms that can reproduce which may not have the most favourable phenotype for survival but may be of economic value or aesthetic appeal, changes allelic frequencies, decreases amount of heterozygotes.

Artificial Insemination: Humans take gametes from a male with a particular trait that they want in offspring and insert it into the uterus of may different females(can be across the world), results in a particular allele being predominant, could cause loss of favourable alleles and will change allelic frequencies such as loss of genetic variation

Cloning: (Nuclear Transfer) Remove nucleus of an egg(encleate) and insert donor DNA from donor somatic cell a fuse together via an electric pulse, simulating the development of an embryo, this embryo can now either be inserted into the organism which donated the egg producing an organism genetically identical to the one which donated the nucleus or be harvested for embryonic stem cells for use in regenerative medicine.

(Embryo Splitting) Also splitting of an embryo cloning which uses an developing embryo and and splits it into 2 different embryos, and then are coated with a solution that propagates further division then can be inserted into surrogate individuals, to produce 2 genetically identical organisms.

Both these methods results in reduction of genetic variation.

Genetic Screening: Analysis of a DNA sample of a person to check whether in their genome they carry a allele of a particular inherited disorder.
 
Gene Therapy: insertion of a normal functioning allele into an organism that has a faulty allele at that gene locus, results in people who have disorders to be able to survive and able to reproduce allowing those detrimental genes to stay in the gene pool.

The rest of the stuff is mainly in bacterial transformation and stem cells.

[StupidProdigy]

results in people who have disorders to be able to survive and able to reproduce allowing those detrimental genes to stay in the gene pool.

Awesome summaries man! Can you please explain to me why it is that the bad genes stay in the gene pool if they've been replaced the a new allele, I don't get it  Thanks!

[Biology24123]

So human impact on evolution is quite easy to understand if you understand the means of natural selection.

Selective breeding: Humans act as the selective agent, choose organisms that can reproduce which may not have the most favourable phenotype for survival but may be of economic value or aesthetic appeal, changes allelic frequencies, decreases amount of heterozygotes.

Artificial Insemination: Humans take gametes from a male with a particular trait that they want in offspring and insert it into the uterus of may different females(can be across the world), results in a particular allele being predominant, could cause loss of favourable alleles and will change allelic frequencies such as loss of genetic variation

Cloning: (Nuclear Transfer) Remove nucleus of an egg(encleate) and insert donor DNA from donor somatic cell a fuse together via an electric pulse, simulating the development of an embryo, this embryo can now either be inserted into the organism which donated the egg producing an organism genetically identical to the one which donated the nucleus or be harvested for embryonic stem cells for use in regenerative medicine.

(Embryo Splitting) Also splitting of an embryo cloning which uses an developing embryo and and splits it into 2 different embryos, and then are coated with a solution that propagates further division then can be inserted into surrogate individuals, to produce 2 genetically identical organisms.

Both these methods results in reduction of genetic variation.

Genetic Screening: Analysis of a DNA sample of a person to check whether in their genome they carry a allele of a particular inherited disorder.
 
Gene Therapy: insertion of a normal functioning allele into an organism that has a faulty allele at that gene locus, results in people who have disorders to be able to survive and able to reproduce allowing those detrimental genes to stay in the gene pool.

The rest of the stuff is mainly in bacterial transformation and stem cells.

Thanks. This is great

[Sine]

Awesome summaries man! Can you please explain to me why it is that the bad genes stay in the gene pool if they've been replaced the a new allele, I don't get it  Thanks!

Probably not exactly in the vce course but my understanding is that there are two types of gene therapy, one for somatic cells only and for germline cells if it is for somatic cells the favourable allele is inserted into all somatic cells resulting in a normal phenotype but not inserted into germline cells and this allele cannot be passed to offspring, germline gene therapy is also pretty self explanatory alleles are inserted into germline cells and will be inherited by offspring, apparently germline gene therapy is illegal due to ethical reasons and that we dont have enough info to know the impact it will have kn future generations.

[cosine]

Are these correct:

- Primates -> Hominoids -> Hominids -> Hominins -> Humans?
- All hominins are bipedal? Well only hominins alive today are humans, but are all the extinct/ancestral hominins bipedal?
- Are ONLY hominins bipedal? (in terms of VCE)

Do we need to know:

- Which primates fall under the categories of hominoids, hominids and hominins?
- All the hominin ancestors of humans?

Anyone?

[Zodiac_2852]

Anyone?

(Bear with me this is my first post)
What you wrote (the top half) is correct.
- hominoid: all apes, gibbons, chimps, orangutans and humans.
- hominid: modern and extinct apes, humans, chimps, gorillas and orangutans (excluding the gibbon).
- hominin: modern and extinct human species.

[tashhhaaa]

hey guys, I'm a bit stuck:

what's the difference between humoral and cell mediated immunity?
do they work together? or does the humoral THEN cell mediated occur?
also
is every mature B cell unique ie. does it have different antibodies?

[cosine]

hey guys, I'm a bit stuck:

what's the difference between humoral and cell mediated immunity?
do they work together? or does the humoral THEN cell mediated occur?
also
is every mature B cell unique ie. does it have different antibodies?

- What's the difference between humoral and cell mediated immunity?
The humoral immune response is the collection of responses involving B cells only. So the proliferation of B cells into plasma and memory B cells, and the secretion of anitbodies is all part of the humoral immunity.

The cell-mediated immune response is the collection of responses involving T cells only. Including the action of Helper T cells, the action of Cytotoxic T cells and supressor T cells.

- Do they work together?
Yes. Firstly, pathogens are engulfed by APCs (antigen presenting cells) and their antigenic material is presented on MHC II markers of the APCs. A specific Helper T cell will come along to the macrophages and upon binding to this MHC II marker, it will get activated. So this activated Helper T cell will then probably do both of:
i). Find a specific Cytotoxic T cell and activate it, if this is the case of a viral infection.
ii). Find specific B cells which have already encountered the antigen, and activate them to proliferate into memory and plasma B cells.

So technically, the cell-mediated occurs first because T Helper cells help B cells to get activated, and so helper T cells get activated first.

- Is every mature B cell unique?
Every mature B cell will ONLY possess one and only one specific antibody to an antigen. There may be like many B cells that possess the same antibodies because they are memory cells, or they may be inactivated B cells which are actually the only ones that possess the antibody, which is a reason as to why first reactions are slow, because there is only a few B cells with that antibody for the antigen, hence a longer time for it to be detected.

Hope this helps

[Biology24123]

- What's the difference between humoral and cell mediated immunity?
The humoral immune response is the collection of responses involving B cells only. So the proliferation of B cells into plasma and memory B cells, and the secretion of anitbodies is all part of the humoral immunity.

The cell-mediated immune response is the collection of responses involving T cells only. Including the action of Helper T cells, the action of Cytotoxic T cells and supressor T cells.

- Do they work together?
Yes. Firstly, pathogens are engulfed by APCs (antigen presenting cells) and their antigenic material is presented on MHC II markers of the APCs. A specific Helper T cell will come along to the macrophages and upon binding to this MHC II marker, it will get activated. So this activated Helper T cell will then probably do both of:
i). Find a specific Cytotoxic T cell and activate it, if this is the case of a viral infection.
ii). Find specific B cells which have already encountered the antigen, and activate them to proliferate into memory and plasma B cells.

So technically, the cell-mediated occurs first because T Helper cells help B cells to get activated, and so helper T cells get activated first.

- Is every mature B cell unique?
Every mature B cell will ONLY possess one and only one specific antibody to an antigen. There may be like many B cells that possess the same antibodies because they are memory cells, or they may be inactivated B cells which are actually the only ones that possess the antibody, which is a reason as to why first reactions are slow, because there is only a few B cells with that antibody for the antigen, hence a longer time for it to be detected.

Hope this helps

T helper cells are also needed to activate B cells to proliferate, not only T cells.

[cosine]

for the attached, when do we know to start a fresh punnet square to work out the probability, as opposed to use the probability from the co-existing offspring?

[cosine]

two questions for the attached: (14)

1. you see how they give us the amino acid sequence, do we assume that the corresponding DNA sequences for those amino acid sequences were all exon regions on the actual DNA molecule in the nucleus?

2. why is B incorrect? I cannot make out why, because deleting the 12 nucleotide will result in the change of the fourth amino acid, am i missing something?

[cosine]

why is B incorrect?

if the organisms are each genetically identical at a particular single gene locus, then they all have the same allele for it right? So should they not all possess the same phenotype? But because it is polygenic, despite being identical at this single loci, they are different at the others and so an example of polygenic inheritance?

[Biology24123]

why is B incorrect?

if the organisms are each genetically identical at a particular single gene locus, then they all have the same allele for it right? So should they not all possess the same phenotype? But because it is polygenic, despite being identical at this single loci, they are different at the others and so an example of polygenic inheritance?

 The answer is C. Phenotype = genotype interaction with the environment. The trait is controlled by one gene only so how is it polygenic