Question: Hello Ian why are some genes more dominant than others????

Ian Simpson answered on 16 Jun 2014:

Pushy parents 😉

The idea of “dominance” can be interpreted in different ways. The “classical” genetic definition of dominance normally relates to different types of the same gene. An example of this would be from the work of the famous Geneticist Gregor Mendel who studied the genetics of pea plants.

He found that a number of pea plant “traits” such as seed shape, flower colour, stem length etc. exhibit dominance. In the case of seed shape, the plant has two types of the gene that controls seed shape, the one that produces round seeds is dominant over the one that produces wrinkled ones.

Mendel never knew anything about DNA as it hadn’t been described back in the 19th Century, but as recently as 1990 scientists finally discovered the gene that encodes the seed shape trait. It turns out to be an enzyme involved in the metabolism of starch. The dominant form produces a functional enzyme (leading to a round seed) and the recessive form fails to make a functional enzyme (leading to a rough seed).

There are other kinds of things that you might think of as dominance when it comes to genes. For example you might think of “competition” between the products of genes for a limited resource. If one gene product was more efficient at using that resource you might interpret that as it being “dominant” over the other one, for example.

If you’re interested in genetics there are some great books out there, you might enjoy Steve Jones’ “The Language of the Genes” which is a very accessible and entertaining read.