Useful Cell and DNA basics

A good DNA Video to jump start the learning....

You can use a microscope to look inside a human cell and find the different types of DNA. Inside ALL the cells in our body, there are many different components given the name of organelles. Don't get hung of this as they are just things that are separated from the other Cell components by a membrane and can be identified. The two organelles that are most important for discussions about human DNA and genealogy are the Nucleus and the Mitochondria.

The large structure on the bottom right of this image is the nucleus, containing the cell's DNA. Mitochondria, which are approximately the SIZE OF BACTERIA and which are surrounded by their OWN MEMBRANE, lie outside of the nuclear membrane in the cytoplasm. The tiny dark bodies in the cytoplasm are ribosomes, and starch granules.

Ribosomes are the structures upon which proteins are made; ALL cells contain these. They are separated from the other Cell components by a membrane and composed of ribosomal proteins (riboproteins) and ribonucleic acids (ribonucleoproteins). The word ribosome is made from taking ‘ribo’ from ribonucleic acid and adding it to ‘soma’, the latin word for body. Ribosomes are bound by a membrane but they are not membranous.

In the nucleus of each cell there are 23 pairs of Chromosomes, - one pair being the sex chromosomes (two X's in women and an X and a Y in men) and the 22 other pairs are usually referred to as autosomal(or atDNA for short).

There is also a completely different kind of DNA, called Mitochondrial DNA (or mtDNA for short). Mitochondria are the power generators in each cell.

There are different inheritance patterns for these different types of DNA and understanding this is key to what test you should order and consider while setting your search goals for genetic genealogy. Through the biological process of DNA replication our DNA is duplicated. We get 23 chromosomes from our father, 23 chromosomes from our mother, AND all our mtDNA from our mother.

Mitosis and Meiosis

Cells divide and reproduce in two ways: mitosis and meiosis. Mitosis is a process of cell division that results in two genetically identical daughter cells developing from a single parent cell. Meiosis, on the other hand, is the division of a germ cell involving two fissions of the nucleus and giving rise to four gametes, or sex cells, each possessing half the number of chromosomes of the original cell.

Differences in Purpose

Though both types of cell division are found in many animals, plants, and fungi, mitosis is more common than meiosis and has a wider variety of functions. Not only is mitosis responsible for asexual reproduction in single-celled organisms, but it is also what enables cellular growth and repair in multicellular organisms, such as humans. In mitosis, a cell makes an exact clone of itself. This process is what is behind the growth of children into adults, the healing of cuts and bruises, and even the regrowth of skin, limbs, and appendages in animals like geckos and lizards.

Meiosis is a more specific type of cell division (of germ cells, in particular) that results in gametes, either eggs or sperm, that contain half of the chromosomes found in a parent cell. Unlike mitosis with its many functions, meiosis has a narrow but significant purpose: assisting sexual reproduction. It is the process that enables children to be related but still different from their two parents. [SOURCE]

This page was last modified: Monday, 19-Nov-2018 11:36:16 MST