Understanding Genomes, DNA, and Cell Division
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Genome
A genome is an organism's complete set of DNA, including all of its genes.
Each genome contains all of the information needed to build and maintain that organism.
In humans, a copy of the entire genome—more than 3 billion DNA base pairs—is contained in all cells that have a nucleus.
It consists of DNA (or RNA in RNA-viruses).
The Genome includes both the Nuclear genes, (the coding regions), the noncoding DNA and the Genomes of the Mitochondria and Chloroplasts (in plants).
DNA AND GENES
One series of bases contains information for the production of one protein, while a different series of bases specifies a different protein.
Each series of protein-specifying bases is known as a gene.
DNA is Packaged in Chromosomes
DNA comes packaged in units called Chromosomes.
Chromosomes are composed of DNA and its associated proteins—a combined chemical complex called chromatin.
Matched Pairs
Humans and many other species have two sets of Chromosomes, thus they come in matched pairs, with one member of each pair inherited from the mother, and the other member of each pair inherited from the father.
Such Homologous Chromosomes have closely matched sets of genes on them, although many of these genes are not identical. Human beings have 46 chromosomes.
22 matched (Autosome) pairs and either a matched (Sex) pair of X chromosomes (in females) or an X and a Y chromosome (in males).
Mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.
May or may not produce discernible changes in the observable characteristics (Phenotype) of an organism.
Play a part in both normal and abnormal biological processes including: evolution, cancer, and the development of the immune system, including junctional diversity.
Classification of types of Mutations By effect on structure:
Small-scale mutations
- Substitutions
- Insertions
- Deletions
Large Scale mutations
- Amplifications
- Deletions
- Form functionally distinct fusion genes
Cell Division
Cell division takes place because:
Cells die and need to be replaced.
Cells can only grow so large before they become dysfunctional.
There are times in which an organism needs quantities of new cells above “replacement” level.
Cell division includes:
The duplication of DNA (replication)
The apportioning of the copied DNA into two quantities in a parent cell (mitosis)
The physical splitting of this parent cell into two daughter cells (cytokinesis)
Overview of Meiosis
Original cell has two (2) sets of chromosomes;
The process begins with one (1) round of chromosome duplication, followed by two (2) rounds of cell division,
Ends with 4 cells, called gametes, with one (1) set of chromosomes each.
Only happens in gonads (reproductive organs)
There are two primary stages to Meiosis:
- Meiosis I
- Meiosis II