The second generation of a purebred cross of a h. o.m. o.zygous recessive organism, with a h. o.m. o.zygous dominant organism, contains a ratio of approximately expressed dominant traits to recessive traits. a. 1:1
b. 1:3
c. 2:1
d. 3:1

d. 3:1

Explanation:

A purebred organism is an organism that contains identical alleles for a particular gene e.g rr or RR. According to this question, in a cross between a purebred dominant organism e.g RR and a purebred recessive organism e.g rr, each parent will produce R and r gametes respectively.

Using the gametes in a punnet square (see attached image), a heterozygous organism (Rr) will be produced in the F1 generation. If these heterozygous organism is self-crossed i.e. Rr × Rr, the following F2 offsprings will result;

RR, Rr, Rr, and rr.

RR, Rr and Rr will exhibit dominant traits while rr will exhibit recessive traits. This means that the F2 generation contains a ratio of approximately 3:1 expressed dominant traits to recessive traits.

one centimetre is equal to 0.01 metres

unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.