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!

Independent Assortment

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, Duplication- extra piece duplicated genes

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 Syndrome

XXY - 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

Normal Karyotype

Monosomy

Trisomy

Trisomy

Trisomy

Can you find the mistake?

Can you find the mistake?

Can you find the mistake?

Can you find the mistake?