Inheritance SAC...

[stonecold]

Can anyone confirm if this is correct, as it is on my SAC.

Linked genes are different genes that are found on the same chromosome, and that are therefore usually inherited together.  The closer together two genes on a chromosome, the less likely they are to be involved in crossing over and gene recombination.

The significance of this is that for unlinked genes, inheritance of both of the alleles comes down to the random separation of the two individual chromosomes in anaphase during meiosis.  For both of the alleles to be inherited, the two non-homologous chromosomes must move to the same pole.   However for linked genes, as both the alleles lie on the same chromosome, they will both be inherited together on a single chromosome which separates during meiosis.  Linked genes will therefore both be inherited unless crossing over/gene recombination occurs.

Autosomes are chromosomes 1-22 in humans.  i.e. the non-sex chromosomes.

A genotype is the genetic content of a cell within an organism and varies due to differing versions of the same gene – alleles.

A phenotype is any characteristic or trait of an organism, and is determined by the genotype.  Phenotypes can be physical, such as skin colour, or chemical, such as the presence or absence of particular proteins.  More than one genotype can give rise to the same phenotype.


Also, can someone explain if sex-linked genes influence inheritance of colour physical characteristics in plants?

We did the di-hybrid cross experiment on corn, testing for dominant (purple) and recessive (yellow) genes kernels and also for dominant (smooth) and recessive (wrinkled) kernels.

How would I go about explaining that these genes are not sex linked.

Thanks.

[Russ]

Can anyone confirm if this is correct, as it is on my SAC.

Linked genes are different genes that are found on the same chromosome, and that are therefore usually inherited together.  The closer together two genes on a chromosome, the less likely they are to be involved in crossing over and gene recombination.

Yes. You could be more specific in the second sentence and say that it's recombination between the two genes, not involving the two but that's mostly just me being a semantic bitch.

The significance of this is that for unlinked genes, inheritance of both of the alleles comes down to the random separation of the two individual chromosomes in anaphase during meiosis.  For both of the alleles to be inherited, the two non-homologous chromosomes must move to the same pole.   However for linked genes, as both the alleles lie on the same chromosome, they will both be inherited together on a single chromosome which separates during meiosis.  Linked genes will therefore both be inherited unless crossing over/gene recombination occurs.

Yes. You could mention it's meiosis II but that's probably not necessary.

Autosomes are chromosomes 1-22 in humans.  i.e. the non-sex chromosomes.

A genotype is the genetic content of a cell within an organism and varies due to differing versions of the same gene – alleles.

A phenotype is any characteristic or trait of an organism, and is determined by the genotype.  Phenotypes can be physical, such as skin colour, or chemical, such as the presence or absence of particular proteins.  More than one genotype can give rise to the same phenotype.

Phenotype can be completely unrelated to genotype (ie environment) so you might want to mention that, but otherwise all good.

Also, can someone explain if sex-linked genes influence inheritance of colour physical characteristics in plants?

We did the di-hybrid cross experiment on corn, testing for dominant (purple) and recessive (yellow) genes kernels and also for dominant (smooth) and recessive (wrinkled) kernels.

How would I go about explaining that these genes are not sex linked.

Thanks.

Well I have no idea if sex-linked genes are responsible for colour in plants, but if they are then you would expect a different ratio to the standard 9:3:3:1 (for unlinked genes). If you draw it out, you'll see that a dihybrid cross of sex-linked genes is different (in the XX/XY system, the male parent can't recombine, so you can only get two gamete types).

If the genes you were testing were linked, but you wanted to establish whether or not they were sex linked, you could do further analysis by crossing with genes known to be sexlinked. If they segregated independently, you could conclude the colour genes were on autosomes. To be SURE, you'd also want to test against other sexlinked genes, to rule out the possibility that they were more than 50mu apart.

This does depend on whatever plants use for sex determination, I hate plant biology so I have no idea.

[stonecold]

Thanks Russ, much appreciated.  SAC went pretty well.  I got another one this Thursday.

*sighs*

[bar0029]

can anyone remember some of the questions of the Drosophila melanogaster sac?
AND did you guys do the copper resistance gene one in bacteria?

[akira88]

can anyone remember some of the questions of the Drosophila melanogaster sac?
AND did you guys do the copper resistance gene one in bacteria?

Lol I have a SAC on that on Monday :S As if we can remember what we did last week at the excursion =.=

[bar0029]

exactly my point lol!
how annoying, it sucks you have the sac same day as we get our exam marks

[Russ]

can anyone remember some of the questions of the Drosophila melanogaster sac?
AND did you guys do the copper resistance gene one in bacteria?

Obviously different between schools, but one of my students had one and it was just about crosses and working out offspring and then stuff like test/reciprocal etc.

[onerealsmartass]

I have my melb uni sac on monday same day as we get our results...
and apparently my teacher cant tell us our results or something, we have to wait till we get the letter.