Chapter 11 & 12 Work - Genetics

Derek Lee

Mr. Hillegas

Ap Biology

14 February 2011

Chapter 11 & 12 Work

II. Connections

a.       Gene locus & disulfide bridge- The gene locus is the location for a specific gene on a chromosome which might code for making a specific protein. If the protein undergoes tertiary or proceeds to quaternary folding, further folding into a specification 3D conformation takes place as a result of disulfide bridges, which form between sulfur atoms in neighboring cysteine amino acids.

b.      Nondisjunction & 9-triplet pattern- MTOC’s (Basal Bodies and centrioles/centrosomes) which consist of  microtubules in a 9+3 pattern are responsible for making up the spindle used in separating chromosomes during mitosis and meiosis. Aneuploidy (having one extra or one less chromosome) results from nondisjunction, whereby one or more pairs of chromosomes do not separate as they should during mitosis or meiosis. Thus down syndrome results when a cell does not separate the correct amount of chromosomes into its cell and fails to commit apoptosis.

c.       Autosome & Steroid- As a result of nondisjunctions with autosome chromosomes, alterations occur during the development of certain phenotypes. For example in XXY males who make less testosterone and more estrogen than normal males which may result in short0term memory, learning disabilities, feminizing effects, low sperm counts, high pitched voice, etc. These individuals may receive testosterone injects –sterioids- in order to reverse the feminizing effects.

d.      Polygenic & Glycocalyx- Polygenetics pertain to the combined action of alleles of more than one gene, some traits, which are predispositions to different heart diseases, hypertension, etc as a result of genetic disorders. The glycocalyx also includes the cell-adhesion molecules that enable cells to adhere to each other and guide the movement of cells during embryonic development. It functions for protection, immunity to infection, defense against cancer, transplant compatibility, cell adhesion, inflammation regulation, fertilization, and embryonic development which are important to preventing genetic disorders leading to a variety of polygenic diseases.

III.  The law of segregation says that alleles in homologous chromosomes separate or segregate during gamete formation and unite at fertilization.  It consists of diploid cells that have pairs of genes on homologous chromosomes. The 2 genes of the pair will separate from each other during meiosis and thus be separated into different gametes. The law of independent assortment says that alleles in nonhomologous chromosomes will separate during the formation of gametes. When meiosis ends, and the pairs of homologous chromosomes have migrated to opposite poles. The chromosome which goes to which pole depends on its previous orientation which is random. This results in traits and chromosomes which are inherited independently/transmitted to the offspring independently despite previously  beings gene pairs. After meiosis the law of segregation deals with gametes with one version of each chromosomes which come together to form the zygote with one gene from each parent while the law of independent assortment occurs during metaphase till meiosis ends resulting in an independent distribution of chromosomes.