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Skip to 0 minutes and 8 secondsThis video will give you an introduction to the principles of human genetics before we look at how genetics can be applied to genealogy. DNA, which is present in every cell of the human body, acts as a blueprint for each unique individual. It controls the production of our cells and determines our appearance and characteristics. The most important principle which can benefit genealogists is inheritance. DNA is made up of 23 pairs of chromosomes. 22 of these are known as autosomal chromosomes while the 23rd pair are the sex chromosomes. It is the inheritance of the sex chromosomes that we will focus on here.

Skip to 0 minutes and 58 secondsIf an individual has both an X and a Y chromosome, they will be male while females have two X chromosomes. The pair of sex chromosomes is made up of one inherited from the father and one inherited from the mother. This means that a male child inherits a Y chromosome from his father and an X chromosome from his mother. A female child inherits one X chromosome from each of its parents. Here is an illustration of how this works. John, since he is a male, carries an X and a Y chromosome. He has three sons-- James, John, and William, who all inherit the Y chromosome from their father.

Skip to 1 minute and 47 secondsJohn senior also has a daughter, Ann, who does not carry the Y chromosome because females have two X chromosomes. Each of the three sons also have a son who inherit the Y chromosome from their father. These three grandsons of John senior also each have a son. The Y chromosome has now been passed down three generations from John senior to his great-grandsons John, David, and Hugh. It may or may not have changed in that time and we will consider this later. Finally, going back to John senior's daughter, Ann, we see that she married George. He carries a completely different Y chromosome to Ann's brothers and it is this Y chromosome which is inherited by his son.

Skip to 2 minutes and 44 secondsYou can see that because the Y chromosome can only be inherited from the father, there is an unbroken line of inheritance through which the Y chromosome passes from father to son, very similar to the way in which surnames are passed on. This principle of the inheritance of the Y chromosome is very important to genealogists, as we will see later. The other important feature connected with the inheritance of the Y chromosome is that it does change, or mutate, over a period of time. This makes it particularly useful for genealogists. There are two major types of mutation which can take place and these will be considered later.

Genetics and genealogy

In this video Graham Holton introduces the scientific principles of genetics that are particularly important for use in genealogy.

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This video is from the free online course:

Genealogy: Researching Your Family Tree

University of Strathclyde

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