1.
Calculate the Mendelian ratios from the following crosses? Make sure you make it clear which phenotype goes with which values
E.g. A_D_ = 9: A_dd = 3: aaD_ = 3: aadd =1
When you are calculating the expected ratios what are you assuming about the arrangement of the two genes? a.
HhRr x HHRr
HR Hr hR hr
HR
Hr
HHRR
HHRr
H__R__ 3: H__rr 1 b.
HHRr x HHRr
HR
HHRr
HHrr
HhRR
HhRr
HhRr
Hhrr
HR
Hr
HHRR
HHRr
H__R__ 3: H__rr 1 c.
hhRr x Hhrr hR
Hr
HHRr
HHrr hr
Hhrr hhrr
Hr hr
HhRr hhRr
H__R__ 1: H__rr 1: hhR__ 1: hhrr

2.
Imagine that you actually perform the crosses and produce enough offspring to check if your expected numbers of each phenotype matches closely with the observed numbers of each offspring.
What would you conclude about the arrangement of the two genes (Does it appear that they are they linked and assorting independently OR does it appear that they are unlinked and not assorting independently) when:
The expected numbers are very close to the observed numbers.
The two genes are assorting independently and randomly aligning along the cell equator during metaphase
The expected numbers deviate greatly from the observed numbers.
The two genes are LINKED and are NOT assorting independently and NOT randomly aligning along the cell equator during metaphase
3.
Draw the phases of meiosis describing the behaviour of the chromosomes. Start with two homologous pairs.
Note the question is asking specifically about the behaviour of the chromosomes so make sure that for every stage you talk about the chromosomes. You may add additional information such as cytokinesis occurring in Telophase I and II or nuclear membrane breaking down in Prophase I BUT MAKE SURE YOU TALK ABOUTT HE CHROMOSOMES!!:)
Prophase I: Homologous chromosomes come together (synapsis) and crossing over occurs at the chiasmata. Chromosomes condense (supercoil).
Metaphase I: Homologous chromosomes align along the equator of the cell.
Anaphase I: Homologous chromosomes separate and are puled to opposite poles.
Telophase I: Chromosomes unwind
Prophase II: Chromosomes supercoil
Metaphase II: Chromosomes (comprised of sister chromatids joined at the centromere) align along the equator of the cell
Anaphase II: Centromere splits and sister chromatids separate and are puled to opposite poles.
Telophase II: Chromosomes arrive at opposite poles.