Meiosis and Sexual Reproduction

Primary benefit of sexual reproduction

It allows offspring to be more genetically diverse. 

Why do cells need to go through meiosis for sexual reproduction?

In order to reduce the number of chromosomes in a offspring in order to keep them same ploidy. 

Where (in the body) does meiosis occur? Can you recognize that this applies to all organisms that have sexual reproduction? 

It would occur in the sex organs of an organism. It does. 

Understand the concept of :reduction division”.

The amount of chromosomes is being reduced by half. 

Identify where in meiosis the ploidy of cell changes.

When the homologous chromosomes are pulled a part they are haploid after meiosis I. 

Describe what is unique about what aligns along the metaphase plates in metaphase I versus metaphase II. 

In metaphase I (meiosis I) the homologous chromosomes are separated. In metaphase II (meiosis II) the homologous pairs are no longer together; sister chromatids are separated. 

Describe how Anaphase I is different from Anaphase II (or really, what is the overall difference between meiosis I versus II?). 

In anaphase I the homologous chromosomes are pulled apart. In anaphase II the sister chromatids are pulled apart. 

How is genetic variation generated in meiosis?

Law of independent assortment: Says that each chromosome is a random assortment. How in metaphase I the homologous chromosomes line up independently. 

In Prophase I the homologous are coming together and swapping regions of DNA. 

Law of segregation: Alleles separate in anaphase how different alleles are pulled into different cells. 

independent assortment

is shuffling the chromosomes 

crossing over generate

Generate recombination chromosomes, regions of DNA from mom and regions of DNA from dad. Some cells/gametes from mom and then some dad. 

Random fertilization

Which sperm is going to be fused with the egg. Each gamete is going to have slightly different DNA. Exception is identical twin; the zygote splits after fertilization occurs.  

Phenotype

Physical characteristics. Determined by genotype and environmental factors. 

Zygote

Occurs after fertilization occurs. Sperm AND egg.

Ploidy

How many complete sets of chromosomes does a cell have. Ex. Haploid, diploid 

Gametes

They are daughter cells in meiosis. What meiosis is making. Sex cells, they are egg and sperm. Haploid. 

Germ cells

Are the parent cells in meiosis.  

Synaptonemal Complex

Holds homologous together during prophase I. When the chromosomes come together to swap DNA they form the synaptonemal complex. 

Chiasmata: Sites of crossing over (maintained through metaphase I). Regions of DNA that are swapped. Prophase I 

Chiasmata

Sites of crossing over (maintained through metaphase I). Regions of DNA that are swapped. Prophase I