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!
Chromosome Mutations are spontaneous changes involving an entire chromosome or pieces of a chromosome Remember Mutations?
Can occur during meiosis Some harmful, some not Bigger effect than gene mutations 2 types: Structural mutations and Numerical Mutations Chromosome 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 Structural Mutations
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 What’s the Mutation?
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 Numerical Mutations
XXY - 47 Males The most common sexchromosome disorder. ~1/1000 males Males are usually infertile. Klinefelter’s Syndrome
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!!! Numerical Changes
46 (23 pairs) What are pairs 1-22 called? Autosomes What is the 23rd pair called? Sex chromosomes Male? Female? XY XX How many chromosomes does a human have?