Down's syndrome in humans is due to:
Held on 30 Apr 2013 · Verified 9 Jul 2026.
three ' X ' chromosomes
three copies of chromosome 21
monosomy
two ' Y ' chromosomes.
Sign in to track your attempts and accuracy.
Sign in to keep a private note on this question. Nothing you write is ever public.
With the help of given pedigree, find out the probability for the birth of a child having no disease and being a carrier (has the disease mutation in one allele of the gene) in $F_3$ generation. 
What is the pattern of inheritance for polygenic trait?
Genes $R$ and $Y$ follow independent assortment. If RRYY produce round yellow seeds and rryy produce wrinkled green seeds, what will be the phenotypic ratio of the F2 generation?
A pink flowered Snapdragon plant was crossed with a red flowered Snapdragon plant. What type of phenotype/s is/are expected in the progeny?
In a plant, black seed color (BB/Bb) is dominant over white seed color (bb). In order to find out the genotype of the black seed plant, with which of the following genotype will you cross it?
Work through every NEET UG Principles of Inheritance and Variation PYQ, year by year.