Select the correct statement:

Identify the contribution of the following scientists: Hugo de Vries,Carl Correns,and Erich von Tschermak.

Statement-$1$: Alleles are slightly different forms of the same gene.
Statement-$2$: The segregation of alleles is a random process and so there is $50$ percent chance of a gamete containing either allele.

For geneticists,the year $1900 \, AD$ is of high significance due to:

Select the incorrect statement from the following.

$A$ disease is caused by a dominant gene,but it shows only $20\%$ penetrance. $A$ heterozygous man marries a homozygous normal woman. What proportion of the children in the population is expected to have the disease?