You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), br (red), bg (green), and by (yellow). B is dominant to all the other alleles, and by is recessive to all the other alleles. The bg allele is dominant to by but recessive to br. You cross a brown (B/by) spider with a pure-breeding green spider. Predict the phenotype of the progeny.

Explanation:

Given;

B allele is for brown color, so B = brown,

br= red,

bg= green,

by= yellow.

B is dominant over all;

bg is dominant over by;

br is dominant over bg;

by is recessive to all other alleles.

Here,  cross between  brown (B/by) and pure green (bg/bg).

B/by× bg/bg

progeny

Genotype= B/bg, B/bg, by/bg and by/bg.

Phenotype= B/bg= brown;

by/bg= green

So, 1/2 are brown and 1/2 are green.

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.