Biology Questions and Answers

Biology Questions and Answers

second interaction leads to blue feathers
and the double recessive ileads to white feathers. nteraction

Each complindependently frementary gene segregatesom the others since
they are located in different

chromosomes. Tfollows Mendel’s secoherefore the patternnd law (although it (^)
does not obey Mendel’s first law).

8. What is epistasis? What is
   the difference between
   dominant epistasis and
   recessive epistasis?

Epistasisa gene (the epistatic gene) can disallow is the gene interaction in which

the phenotypical manifanother gene (the hypostaticestation gene). In of (^)
dominant epistasis the inhibitor allele is
the dominant allthe epistatic gene so inhibition ele (for example, occurs inI) of (^)
dominant homozygosity (II) or in
heterozygosity (Iiepistasis the inhibitor allele ). In recessiveis the (^)
recessive allele so inhibition occurs only of the epistaticin recessive gene (i)
homozygosity (ii).

9. In the hybridization of 2
   genes (4 different alleles, 2 of
   each pair) how does epistasis
   affect the proportion of
   phenotypical forms in the F2
   generation?

In dihybridism without epistasis double
heterozygous parental inand in F2 4 phenotypical forms apdividuals crosspear.
The proportion is 9 double dominant to

3 dominant for the first pair, recessive

for the second to 3 recessivefirst pair, dominant for the second to 1 for the (^)
double recessive (9:3:3:1).
Considering that the epistaticthe second pair and that the recessive gene is (^)
genotype of the hypostaticlacking of the characteristic, gene means in the F2
generation of the dominant epistasis the
following emerge: 13 dominant for the secondphenotypical forms would (^)
pair or recessive for the first, i.e., the
characteristicdominant for the first pair, recessive does not manifest, 3 (^) for
the second, i.e., the characteristicmanifests. The phenotypical proportio (^) n
would be 13:3. In the recessive
epistasisthat would emerge are: 9 double in F2 the phenotypical forms
dominant (the characteristic manifests),
7 recessive ffor the second, i.e., the characteristicor the first pair or recessive
does not manifest. So the phenotypical
proportion would be 9:7.
These examples show how epistasis
changes phenotypicalproportions, from the normal 9:3:3:1 forms and (^) in
F2 to 13:3 in dominant epistasis or to
9:7 in recessive esome forms have even disappeared).pistasis (note that
(If the recessive ghypostatic gene is active, not enotype of thesimply (^)
meaning that thnot manifest, the number ofe dominant allel e does
phenotypical forms in F2 changes.)
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