Download - MEIOSIS Round 2
Compare Critical differences
between Mitosis and Meiosis:
Tetrads form (Pro I) Crossing over can
occur (Pro I) Tetrads line up and are
separated (Meta I) Daughter cells are
haploid Only occurs in germ
cells Produces gametes
(ova and sperm)
Mitosis vs. Meiosis I
Left: Metaphase of MITOSIS: no pairing!!!!
Right: Metaphase I of Meiosis: homologous chromosomes Pair UP!
Remember Mutations?Chromosome Mutations are
spontaneous changes involving an entire chromosome or pieces of a chromosome
Chromosome Mutations• Can occur during
meiosis• Some harmful,
some not• Bigger effect than
gene mutations• 2 types: Structural
mutations and Numerical Mutations
Structural Mutations• change in arrangement of genes on
a chromosome
• For example, Deletion- one or more genes are lost
Structural Mutations• Another example…. Inversion- piece
of a chromosome breaks off and reattaches itself backwards
Structural Mutations• Another
example, Translocation- piece of a chromosome breaks off of one & attaches to another different chromosome
What’s the Mutation? QRSTUV to QRUTSV Inversion UVWXY to ABCDUVWXY Insertion/Addition LMNOP to LMNLMNOP Duplication ABCDEF to ABEF Deletion What TYPE of mutations are these? Structural - change in arrangement or # of genes What causes them? Problems with crossing over
Numerical Mutations• changes in the
number of chromosomes in a zygote
• Usually results from nondisjunction- failure of chromosomes to separate
• Monosomy- zygote receives only 1 of a particular chromosome
• EX: female being XO or getting 1 # 6 chromosome
Numerical Mutations• Trisomy- zygote receives 3
chromosomes of a particular kind
• Down’s Syndrome - extra 21st chromosome
Klinefelter’s SyndromeXXY - 47 Males
The most common sexchromosome disorder.
~1/1000 males
Males are usually infertile.
Numerical Changes• Polyploidy- none
of the chromosomes separate and the zygote gets 3 or more sets of chromosomes
• EX: instead of 23 pairs, you get 46 pairs of chromosomes…this means 92 chromosomes!!!
How many chromosomes does a human have?
46 (23 pairs)What are pairs 1-22 called?AutosomesWhat is the 23rd pair called?Sex chromosomesMale? Female?XY XX