VCE Biology Question Thread

[katiesaliba]

Can someone please explain linked and unlinked genes?

As aforementioned, linked genes are genes whose loci are on the same chromosome. If no crossing over occurs during prophase 1 in meiosis, then the DNA in gametes will be identical to their parents (i.e. parental type). However, if crossing over occurs then some recombinant gametes (recombinant types) will be created. Remember, crossing over is most likely to occur between genes that have loci which are farther apart (but by less than 50 map units by memory). The offspring will always have a greater ratio of parental type to recombinant type DNA (2:1:1:2) after fertilisation involving linked genes. This is an identifying feature. If offspring are in a 1:1:1:1 ratio, then the genes have been independently assorted during meiosis (i.e. not linked but on separate chromosomes which have been independently assorted during anaphase 1). To unlink genes, a translocation mutation would have to occur.
Hope this helps! (Excuse the essay. This is just me revising )

[katiesaliba]

Would an increased brain size increase the number of neural connections/neurons within the brain? So, would homo sapiens have evolved more neural connections due to an increased brain capacity?

[shivaji]

What exactly is meant by purebreeding organisms and a pure breeding cross? Is it that they are both homozoygous recessive for a trait or can one be homozoygous dominant and the other partner homozygous recessive?
Also, would all of their anscestors been the same? (i.e. all homozozygous recessive?)

[dankfrank420]

Therapeutic cloning involves the production of cloned tissues/cells, while reproductive cloning involves the production of cloned organisms.  If this is the case, then why is Somatic Cell Nuclear Transfer an example of therapeutic cloning if it involves making an individual?

[anat0my]

As aforementioned, linked genes are genes whose loci are on the same chromosome. If no crossing over occurs during prophase 1 in meiosis, then the DNA in gametes will be identical to their parents (i.e. parental type). However, if crossing over occurs then some recombinant gametes (recombinant types) will be created. Remember, crossing over is most likely to occur between genes that have loci which are farther apart (but by less than 50 map units by memory). The offspring will always have a greater ratio of parental type to recombinant type DNA (2:1:1:2) after fertilisation involving linked genes. This is an identifying feature. If offspring are in a 1:1:1:1 ratio, then the genes have been independently assorted during meiosis (i.e. not linked but on separate chromosomes which have been independently assorted during anaphase 1). To unlink genes, a translocation mutation would have to occur.
Hope this helps! (Excuse the essay. This is just me revising )

Thanks that was helpful! Appreciate the essay

[RazzMeTazz]

In relation to fossils is mineralisation and petrification the same thing?

[RazzMeTazz]

Would it be correct to assume that homologous structures have formed as a result of different selection pressures (hence the function of the structures are different)

And analogous structures formed due to organisms under similar selection pressures (so different structures became used for similar functions? )

[katiesaliba]

Would it be correct to assume that homologous structures have formed as a result of different selection pressures (hence the function of the structures are different)

And analogous structures formed due to organisms under similar selection pressures (so different structures became used for similar functions? )

Yep

[katiesaliba]

Does the topic of 'designer babies' encompass genetic engineering or does it purely involve artificial selection of zygotes? SAC TOMORROW SOMEONE PLEASE HELP CLARIFY 

[grannysmith]

Does the topic of 'designer babies' encompass genetic engineering or does it purely involve artificial selection of zygotes? SAC TOMORROW SOMEONE PLEASE HELP CLARIFY 

I'd say genetic modification

[RazzMeTazz]

What do fossils allow us to infer about the relatedness of organisms?

[katiesaliba]

Is genetic engineering an example of artificial selection?

[katiesaliba]

I don't think so. Artificial selection is just the selection by humans of which members of a population will breed to produce the next generation. The organisms DNA is not altered in the process. Genetic engineering, however, is the direct manipulation of DNA.

Thanks! But isn't that selective breeding, or are both terms interchangeable?

[grannysmith]

Thanks! But isn't that selective breeding, or are both terms interchangeable?

Selective breeding = artificial selection

[grannysmith]

Is genetic engineering an example of artificial selection?

Genetic engineering has to involve the use of genetic techniques, artificial selection does not