Posted 7/25/2015 12:45 PM (GMT -5)
I know this is late, but I wanted to pass along some information.
The way genes work is that you have two copies of each gene in every cell of your body. The DNA structure looks like a ladder and the steps are made up from the two genes (joined together). Those genes (or steps) determine what color your hair and skin are along with everything about you physically.
The only cells in the body that don't have the ladder with it's two genes are eggs and sperm. Each egg and each sperm have 1/2 of the ladder, therefore only one gene. When a sperm fertilizes an egg, the two pieces of ladder join to give the child their DNA structure with the steps made up of one gene from mom and one from dad.
If you have a gene mutation and it is listed as (+/+) it means you have two copies of the mutated gene. If it's listed as (+/-), it means you have one copy of the normal gene and one mutated gene.
The tricky part is that the mutation could be recessive or dominant. If you have one dominant gene then it doesn't matter what the other gene is, that characteristic will occur. For a recessive trait like hazel eyes to show, you must have two copies of the recessive gene (or mutation).
For example, my eye color is hazel (Blue-green) which is always recessive. My husband has Brown eyes which is a dominate trait. Since he is Italian and both his parents have brown eyes and all their ancestors have brown eyes, it pretty likely that he has two brown eyed genes to pass on. I only have the hazel eye gene to pass on to my kids. Both kids have brown eyes. They could have hazel eyed children if their partner has the hazel eyed gene.
It's why two non-red haired parents can have a red headed child. If they both carry a gene for red headedness, it wouldn't show in them. However, if they both passed a copy of that gene to their child, the child would have red hair.
For a recessive trait like hazel eyes to show, you must have two copies of the gene (or mutation). For a dominateSo when I got pregnant, my egg contained one copy of a gene for Hazel eyes.
The next tricky part is gene expression. Some traits caused by a specific gene may or may not occur or occur in a limited amount. This is genetic expression. A good example is a calico cat. The cat's cells contain genes for the different colors, but within each cell a different gene may be activated. So when you compare the different hairs one may be black, one white or one orange. In some cases you might have all the colors on the same hair. For these types of genes the amount that it is expressed can vary.
So, (+/+) doesn't mean it is more likely to effect you. (+/-) doesn't mean it it less likely to effect you. If the mutation is dominant, it means either way it will effect you. If the gene is one that is dormant until something happens to cause it to be expressed, then with (+/+) it will be expressed. If the gene is one that is dormant until something happens to cause it to be expressed then with (+/-), then you have a 50/50 chance it will be expressed.
Some genes just sit there dormant until something triggers them to become active and express themselves. It's a reason why we might not see the effects until later in life or not at all.