How could one determine is an organism is homozygous or heterozygous?

Answer 1

im guessing we are assumeing there is not obvious phenotype to tell us what the genotype is then (otherwise the answer is simply, look).

if you know the area around the gene you are looking at you could amplify it by PCR and sequence it. if your organism is hetrozygous, you will get two peaks for each possition where the alleles don't have the same sequence.

alternitively, if the two alleles are sugnificantly different, you could design separate PCR primers, to give different sized PCR products depending on what allele they annealed to. therfor by looking at the size of your PCR products after being run on an agarose gel, you can determine (if you have one band) if the organism is homozygous or not (if there is two).

also, if one allele has a restriction site in it, again do PCR, but this time digest the DNA with the restriction enzyme and by looking at the products you can determine what alleles were present. only two smaller fragments would be homozygous for the allele with the restriction site, only one large fragment would be homozygou for the allele without and all three fragments would be hetrozygous.

i have assumed your organism is diploid, otherwise you would be required to devise several tests like those above to determine your genotype.

Answer 2

In test cross the female is crossed with homozygous recessive male. If all the off springs of this cross are phenotypically alike, the female parent is homozygous dominant. If half of these off springs are of different type, the female parent is heterozygous.

Answer 3

By test cross.

Answer 4

test cross