Meiosis, Sexual Reproduction, and Pedigrees

Biology

During meiosis, gametes are produced. These are cells that are haploid (i.e., they have ½ the genetic material of a normal cell). Gametes from two different adult organisms are fused during sexual reproduction, creating a new diploid cell that, through mitotic division, will eventually become another adult organism.

Meiosis creates genetic diversity – each new organism is created by mixing the genes from two different parent organisms. Among other things, this increases the likelihood that beneficial mutations will be spread through a population – and decreases the likelihood that harmful mutations will persist in a population.

One way to track genes in a population is to look at a pedigree – a chart that shows how a group of people is related, indicating their gender and whether or not they show the affect of a certain gene. Pedigrees can help us determine the origin of a particular gene, and whether it is dominant (i.e., an organism only needs one copy of that gene to be affected) or recessive (i.e., an organism needs two copies of that gene to be affected). Pedigrees can also help us predict if two organisms are likely to have offspring that will be affected by a particular gene.

Activity: Create a pedigree

1. Go to the website http://pedidraw.gcnet.org.cn/

2. Click on the “Register” button and create a user name and password (you can also see an example pedigree with the user name “bregarbiology” and the password “csd509j”

3. Enter family information for a hypothetical gene that allows a person to have rotating ears – you should enter at least the information for a spouse, two sons, two daughters, both parents, and both sets of grandparents

4. Click on the “Confirmation” button and create a pedigree diagram

5. Working with a partner, make sure that you can identify the gender of each individual on the chart, that you can determine the familial relationships (i.e., brother, sister, mother, father, spouse, grandmother, grandfather), and that you can recognize which individuals will have the ability to rotate their ears

6. Try to determine whether your pedigree chart shows a dominant pattern or a recessive pattern of inheritance – does everyone who has at least one copy of the gene have the ability to rotate their ears? Or do the people on your chart need to have two copies of the gene in order to have this ability?