Does one parent transmit more DNA to the offspring than the other one?

Question

Does one parent transmit more DNA to the offspring than the other one? Or do both parents always transmit the same amount of genetic material to their offspring? In other words, can a baby be provided with a gene from the mother without an "opposite gene" from the father?

Answer 1

There are instances of a parent providing a gene without a corresponding "opposite gene" or allele being provided. The biggest example in a healthy individual is the SRY gene located on the Y chromosome which only comes from the father and it is this gene that essentially "turns on" the machinery that will eventually make an embryo become a male. However, it is possible in diseases for one parent to transmit more DNA to the offspring than the other where there is chromosomal aneuploidy (aneuploidy meaning an abnormal number of chromosomes) where a single parent may "accidentally" provide an extra copy of a chromosome (think Trisomy 21 or Down's Syndrome) or fail to provide a copy at all (Turner's Syndrome where an individual only has a single X chromosome and no extra X chromosome or Y chromosome).