The Benefits of Sexual Reproduction

SEE THE NOTE ABOUT THE READING GUIDE HOMEWORK AT THE BOTTOM.

Today we focused on understanding why sexual reproduction is far more prevalent than asexual reproduction in organisms, although it is much less efficient.  The main factor we discussed as playing a role in sexual reproduction is variation (note: there are several different hypotheses suggested here).  That variation comes from the process of meiosis.  (see links to meiosis from earlier blog posts)

1. Meiosis begins with a single cell containing diploid replicated chromosomes.
2. In Meiosis I homologous chromosomes are separated, resulting in 2 cells containing haploid replicated chromosomes.
3. In Meiosis II sister chromatids are separated, resulting in 4 cells containing haploid unreplicated chromosomes.

The variation comes in at three points:

1. Crossover between non-sister chromatids of homologous chromosomes.
2. Independent assortment of homologous chromosomes at metaphase I.
3. Random fertilization.

On Monday we will be focused on the discovery of DNA structure.

Homework:
You received a reading guide for Ch. 16 in class today.  You only need to complete 16.1 for Monday! 

• If you are in 2nd or 3rd period you received the reading guide for the whole chapter, so ONLY COMPLETE 16.1. 
• 5th and 6th period only received the part of the reading guide that pertains to 16.1 so you must COMPLETE THE WHOLE THING.

See you Monday and have a GREAT 4 days off!!