BL1004: Cellular and Genetic Framework

BL1004: Cellular and Genetic Framework. In this module, you investigate cellular reproduction, genetics, and inheritance. As you\’ve seen in your reading, there are two basic types of cellular reproduction in Eukaryotic cells. As we grow and age, almost all of our cells will reproduce (e.g., split into two identical copies) at some point.

This process is called mitosis. Here is a cartoon of mitosis in a cell that only has two chromosomes (or cells have 46):

Notice the mitosis is divided into various stages depending upon the status of the DNA in the cell. Your text goes into detail about the various stages, and you should be sure to understand the process. However, there is a variation of mitosis that applies to the production of gametes (sperm and egg cells). Gametes or sex cells (i.e., egg and sperm cells) are haploid, which means that they carry 1/2 of the full complement of our genetic code or genome. For our cells to produce sex cells or gametes, they undergo meiosis. Here is a cartoon of meiosis. BL1004: Cellular and Genetic Framework

https://www.yourgenome.org/facts/what-is-meiosis

BL1004: Cellular and Genetic Framework
Now observe at the end of meiosis, we have four rather than two daughter cells and these daughter cells are gametes. Gametes or sex cells (i.e., egg and sperm cells) are haploid, which means that they carry 1/2 of the full complement of our genetic code or genome. Since every individual grows out of the synthesis of two haploid cells, they have a full set of chromosomes and diploid. The 1/2 of the genes that each individual inherits from each parent is essentially random. This means that each child produced by the cross between two people is just one of many different possible genetic combinations. Punnett Square is a simple technique for tracking the possible types of offspring two parents can produce concerning only one of the genes inherited by the offspring.

Each gene can come in different forms called alleles, and each allele is associated with other possible traits. Some alleles can be distinguished as either dominant or recessive, which means that they are doing or do not express themselves in the phenotype of a heterozygote individual. Dominant alleles always express themselves in the phenotype, whereas the traits of recessive alleles are only expressed in the phenotype of homozygotes. Mendelian logic is very useful for tracking the inheritance of these types of alleles. A number of essential diseases are primarily associated with single alleles such as these.

Here are several tutorials on how to use Punnett squares. If you have any discomfort with these tools, please view these!

https://www.youtube.com/watch?v=prkHKjfUmMs
http://www.youtube.com/watch?v=Y1PCwxUDTl8
https://www.youtube.com/watch?v=Y1PCwxUDTl8&t=1s

BL1004: Cellular and Genetic Framework
Punnett squares are also covered in your textbook. Make sure that you also understand the terms: Allele, phenotype, genotype, dominant, recessive, and cross. In particular, be sure you know how to represent a phenotype (one allele), a genotype (two alleles), and a cross (two alleles cross two alleles). Thus, for the alleles shown in the diagram below, there is a dominant allele \”B\” and a recessive allele \”b.\” With these alleles a phenotype is expressed as either \”B\” or \”b\”, a genotype could be \”BB\”, \”Bb\”, or \”bb\”, and the possible crosses could include \”BB x BB\”, \”BB x Bb\”, \”BB x bb\”, \”Bb x Bb\”, \”Bb x bb\”, \”bb x bb\”.

Please do respond after you have reviewed some of the material. What do you find of interest of this new information? Does this help you feel more confident with these materials? Do you have other questions on the subjects covered in this module?

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