Compare Critical differences between Mitosis and Meiosis: Tetrads form (Pro I) Crossing over can occur (Pro I) Tetrads line up and are separated (Meta.

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Presentation transcript:

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 toQRUTSV Inversion UVWXYtoABCDUVWXY Insertion/Addition LMNOPtoLMNLMNOP Duplication ABCDEFtoABEF 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 sex chromosome 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? Autosomes What is the 23rd pair called? Sex chromosomes Male? Female? XY XX

Normal Karyotype

Monosomy

Trisomy

Can you find the mistake?