Mitosis vs. Meiosis No sex vs. Sex Which is better? Mr. Snider SOCES socesbio.com.

Mitosis vs. Meiosis No sex vs. Sex

Which is better?

Mr. Snider

SOCESsocesbio.com

Why do Mitosis?

• Growth 1 cell to billions exponentially

• Maintenance – replace skin, stomach

• Repair- injuries

Why do Meiosis?

• Variation – not FUN– Remember over 50% of sexual reproduction

does not include intercourse

Mitosis vs. Meiosis

• One cell forms 2 exact copies

• 100% of DNA same• Represent all genes

in gene pool• Clones• Susceptible to same

diseases

• 1 cell forms 4 daughter cells, each with ½ the original # of chromosomes

• Genetic recombination

• Increase variation• New combinations

Quick video comparison

http://www.youtube.com/watch?v=Ba9LXKH2ztU

Physical structure vs. genetics

• Physically Meiosis and Mitosis are similar

• IPMAT

• Interphase

• Prophase

• Metaphase

• Anaphase

• Telophase (Cytokenesis)

Mitosis preview – bear with 5 mins

• Awesome video

http://www.youtube.com/watch?v=Q6ucKWIIFmg

Interphase

• Common to both Mitosis and Meiosis

• DNA and organelles copy themselves

• G1 – growth 1 recovery (stop and stay)

• S – synthesis -copying

• G2 – growth 2 get beg for copying (stop)

Prophase

• Chromatin condenses to become visible as chromosomes (sister chromatids)

• Nuclear envelope breaks apart

• Spindle apparatus (spindle fibers and centrosome) formsspindle fibers=microtubules

Animal cell centrosome includes centromere

Metaphase

• Sister chromatids line up in the center of the cell

• (spindle apparatus is fully formed)

Anaphase

• Sister chromatids separate, and chromosomes (chromatids) move to the poles

Telophase (+cytokenesis)

• Spindle apparatus dissolves

• Nuclear envelope reforms• Chromosomes dissolve

into chromatin• Cytokenesis – even

division of organelles between daughter cells

• Cleavage plane in animals

• Cell plate in plants

Summary Mitosis

• One cell forming 2 identical daughter cells

• Growth, Maintenance, repair

• Zygote- you 1000X

• Cloning; Asexual

• Reproduction – yeast?; single celled protists (not bacteria – binary fission)

Review Mitosis

http://www.youtube.com/watch?v=kRWnJd1WRbA

Main Differences

• Mieosis – variation for offspring- gene reduction

• Mitosis – perfect copies to get big enough to do reproduction

• Question – which needs more energy?

• How many times to do reproduction?

Meiosis

• Diploid cell to haploid gamete

• Diploid = 2 copies of chromosomes(2N)

• Haploid = 1 copy (N or 1N)

• If you add 2N+2N during sex BAD things happen, so you must reduce 1st

• 2 times = Interphase +Meiosis 1 (P-T) + Meiosis 2 (P-T) = 9 phases

• DNA changes only – physical parts same)

Interphase

• Same as in Mitosis – DNA and organelles double (DNA during S phase)

Meiosis I

• Prophase – Tetrads become visible

• Tetrad = Homologous pair or Homologous chromatids

• 2 pairs of sister chromatids that have same genes from different parents

• Crossing over occurs here

Metaphase I

• Tetrads line up in center of cell

Anaphase I

• Tetrads (2 N) separate and Sister chromatids/ Homologous pairs (N) move to the poles

• This is tricky – you only have one set of chromosomes, but 2 copies of that set

Telophase I

• Homologous pairs/ Sister Chromatids sometimes uncondense (most don’t- loss of Energy)

Interphase II

• It’s a trick – don’t fall for it! No such thing!

Prophase II

• (Rest is same as Mitosis)

• Sister chromatids/ Homologous pairs attach to spindle apparatus

Metaphase II

• Sister chromatids/ Homologous pairs line up in center of the cell

Anaphase II

• Sister chromatids/ Homologous pairs separate and Chromasomes/ Chromatids move to poles

Telophase II (+Cytokenesis)

• Chromosomes dissolve into chromatin

• 4 daughter cells, each with ½ original # of chromosomes

Meiosis video

http://www.youtube.com/watch?v=kVMb4Js99tA

Summary (yet again)

• Mitosis – 1 cell forms 2 exact copies

• Asexual reproduction; cloning

• Growth, maintenance, repair

• Mutations lead to uncontrolled cell growth = cancer

• Meiosis- 1 cell forms 4 daughter cells, each with ½ the original # of chromosomes

• Sexual reproduction• Gamete production

(sperm, egg)• Mutations lead to dead

offspring of changes in gene frequency (evolution)

Advice

• Follow up on youtube –

mitosis vs. meiosis videos; there are several good ones.

http://www.youtube.com/watch?v=_llXzrz8oOc