WHAT Creates Unique cells in MEIOSIS ?

1. SYNAPSIS & CROSSING OVER (PROPHASE I)

2. INDEPENDENT/RandomASSORTMENT (Metaphase and Metaphase II)

WHAT MAKES MEIOSIS DIFFERENT ?

Homologous chromosomes pair up during ________________ = ______________SYNAPSIS

Images modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif

This group of FOUR (4)chromatids is called a_________________TETRAD

PROPHASE I

WHAT MAKES MEIOSIS DIFFERENT?

Exchange of DNA betweenhomologous pairs = _____________during PROPHASE I

CROSSING OVER

Allows shuffling of genetic material

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif

Click the image to play the video segment. 11E

Video 5

Crossing Over

SEE CROSSING OVERANIMATION

HOMOLOGOUS CHROMOSOMES

Image modified by Riedell • SAME SIZE• SAME SHAPE• CARRY GENES for the

SAME TRAITS• BUT ______________! (Don’t have to have

the SAME CHOICES)

http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

NOT IDENTICAL

CROSSING

OVER

Image modified by Riedell

• Allows for_________________in different combinations

• After crossing over, chromatid arms are________________ anymore

http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

rearranging of DNA

NOT IDENTICAL

SEGREGATION & CROSSING OVERtogether make even more

combinations

See ananimation

http://waynesword.palomar.edu/lmexer2a.htm

INDEPENDENT ASSORTMENT

http://fig.cox.miami.edu/~cmallery/150/mitosis/c13x9independent-assortment.jpg

INDEPENDENT ASSORTMENTat ANAPHASE I

Lots of different combinations are possible!

This is why you don’t look exactly like your brothers and sisters even though you share the same parents!

http://www.tokyo-med.ac.jp/genet/anm/mimov.gi

WHAT MAKES MEIOSIS DIFFERENT ?

1. Crossing over 2.Independent assortment

are ALL ways MEIOSIS results in =______________________________

So daughter cells are ______________from parents and from each other

differentGENETIC RECOMBINATION

Why Unique Gametes is a GOOD thing!!

Allows for variation in population

Individuals can be different

Provides foundation for EVOLUTION

Allows species to adapt to changes intheir environment

http://naturalsciences.sdsu.edu/classes/lab8/spindex.html

Random Fertilization• Any egg can be fertilized by any sperm.