VCE Biology Question Thread

[soli]

"When looking at Drosophila you came across a male and female with yellow eyes. Suppose the mutation was on an autosome and you wanted to establish if the yellow eyes was dominant or recessive to wild type (red) eyes. Outline the crosses you would carry out to establish which phenotype is dominant. yellow or wild type."

Would the cross just be between a homozygous red eyed fly and a homozygous yellow eyed fly, so that all their offspring would show the dominant phenotype?

[soli]

shouldn't all of them express the dominant phenotype? As I crossed homozygous red eyed fly with a homozygous yellow eyed fly?

[MM1]

-What's the difference between transformation and transfection?

-Can someone please explain the stimulus/response model for ADH [antidiuretic hormone]?

-It is believed that necrosis occurs when a cell has sustained physical or chemical damage. Can apoptosis also occur in such instances where damage is inflicted?

Thanks!

[katiesaliba]

What is the haploid number of organisms with an odd diploid number? For example, if the somatic cells of a male grasshopper have a 2n number of 15, how many chromosomes would be present in their sperm cells?

[lzxnl]

shouldn't all of them express the dominant phenotype? As I crossed homozygous red eyed fly with a homozygous yellow eyed fly?

Oops. Wasn't reading. Somehow read that as heterozygous
My bad.

[DJA]

If genes are linked (on same chromosome) do the allele pairs still undergo Independent Assortment?

[grannysmith]

If genes are linked (on same chromosome) do the allele pairs still undergo Independent Assortment?

No. Remember that independent assortment is defined as the behaviour/segregation of one allelic pair being uninfluenced by the behaviour/segregation of another allelic pair (which are found on different chromosomes). Or there is equal chance that either alleles will end up in either daughter cells.

But because they are located on the same chromosome (hence 'linked'), this factor influences their behaviour/segregation; that is, they tend to be inherited together and therefore the likelihood of them being separated into different gametes is not equal. Thus they cannot be independently assorted.

Does this make sense?

[DJA]

No. Remember that independent assortment is defined as the behaviour/segregation of one allelic pair being uninfluenced by the behaviour/segregation of another allelic pair (which are found on different chromosomes). Or there is equal chance that either alleles will end up in either daughter cells.

But because they are located on the same chromosome (hence 'linked'), this factor influences their behaviour/segregation; that is, they tend to be inherited together and therefore the likelihood of them being separated into different gametes is not equal. Thus they cannot be independently assorted.

Does this make sense?

friggin awesome thanks

[Damo23]

Hey does anyone here know:

The difference between linked and unlinked genes and how it relates to meiosis?

What is continuous variation in simple terms because I've googled it and I've read it in my book but I can't seem to understand it, roughly I think it's variation that doesn't fall into discrete class and I'm trying to understand the human height and weight graphs but I just don't seem to get it 

Thanks to anyone who can help 

[grannysmith]

Linked genes are found on the same chromosome and tend to be inherited together, whereas unlinked genes are found on different chromosomes and assort independently.
So in meiosis, when homologous chromosomes separate, usually there is equal chance that either homologues will end up on either side of the cell equator and thus in either daughter cells. So this translates into the genes having equal chance as well (they're located on the chromosomes).
However, if they are linked genes, then they will always end up together regardless of where the chromosome (on which they are located) ends up. So you can imagine that the gametes will all have the parental genotype for a specific pair of linked genes. However, crossing over allows for recombinant gametes to be produced.

Continuous variation is a result of many genes interacting plus the effect of the environment. So you don't get discrete, distinguishable groups like you would in eye colour (brown or blue) as these are produced by single genes. Basically, you get a greater variation in continuous variation. E.g. height
So when it comes to graphs, you get a normal distribution curve and not like bar graphs.

[Damo23]

Thanks so much 

[Sense]

In this 5 part question on a practice sac, there's a cross between a heterozygous male (Dd) and female (Dd).

There is a question asking 'how many different types of gametes can the female produce with respect to the Rhesus gene? What are they, and what is the probability of each kind?' (The Rhesus blood type is the one being investigated in the cross)

It would be two, right? D and d and a 50% of each.

I feel stupid asking this, I'm just making sure that it isn't 3, Dd DD and dd (the children), because there are similar questions that I googled and people give this answer.

[Scooby]

In this 5 part question on a practice sac, there's a cross between a heterozygous male (Dd) and female (Dd).

There is a question asking 'how many different types of gametes can the female produce with respect to the Rhesus gene? What are they, and what is the probability of each kind?' (The Rhesus blood type is the one being investigated in the cross)

It would be two, right? D and d and a 50% of each.

I feel stupid asking this, I'm just making sure that it isn't 3, Dd DD and dd (the children), because there are similar questions that I googled and people give this answer.

Nah, you're right - she'll produce "D" and "d" gametes (50% of each)

[soNasty]

can someone explain to me how these crosses work? (involving linked genes) im confused at the way theyre set out

[vox nihili]

(Image removed from quote.)

can someone explain to me how these crosses work? (involving linked genes) im confused at the way theyre set out

Don't worry about it, it's too much for year 12