Scribe Post 11/7

Today in class we:

1. Turned in the homework, UP pages 3-4, 9-11, and our spice lab write up


2. Finished the meiosis notes


3. Watched a video on meiosis

In the video, we reveiwed the process of sexual reproduction in cells, and got more into depth with crossovers in chromosomes, exchanging genetic information thus adding diversity to the cell.

IN THE NOTES:

In the notes in class, we began with explaining the 3 resons for variety in species:

1. 
   
   Independent Assortment: the arrangement of the homologous chromosome pairs at metaphase 1 varies and is a matter of chance. Each pair orients itself independently of the other pair. This affects the the resulting gametes=variety. Each human gamete has 8 million possible combinations.


2. 
   
   Random Fertiliazation: 1 egg (8 million possible combinations) with 1 sperm (8 million possible combinations) results in 64 trillion different potential combinations.


3. 
   
   Crossing Over: This is the exchanging of genetic information by homologous chromatids, creating a genetic recombination.

After this, we moved on to explaining possible errors that may occur during meiosis:

1. 
   
   Nondisjunction: This is when the chromosomes fail to seperate during Anaphase I or II. This occurs with autosomes or sex chromosomes, thus leading to a mutation.

Some examples of a mutation or disorder caused by a nondisjunction are:





• Trisonomy 21 (Down Syndrome): This is when a nondisjunction occurs in the 21st chromosome, resulting in three (a trisonomy) of chromosome 21.


• Klinefelter Syndrome- male XXY: This syndrome occurs when the X chromosome fails to seperate and the male is left with two X chromosomes and a Y


• Turner Syndrome- female XO: This syndrome also occurs in the X chromosome, except the female is missing an X chromosome due to a disjunction

2. Breakage of a chromosome:

• Deletion: if a fragment of genetic information is lost, the remaining chromosome has a deletion


• Duplication: If a fragment of a chromosome is inserted into another homologous chromosome, it produces a duplication there.


• Inversion: If a fragment of genetic information is detatch from the chromosome and then retatched in the reverse direction, an inversion has occured


• Translation: If a fragment of genetic information attatches to a nonhomologous chromosome, a translation of genetic information has occured.

Tonights homeworks is:

• Cut out page 21 and put it in a SEPERATE bag from your assigned page (B, C, or D)


• Study for quiz.

Next Scribe: ***Eleni***