Meiosis S1M1

Sex Cells

Gametes

Gametogenesis

The cells that give rise to the sex cells

From the wall of the yolk sack

• 1. They don't make identical copies the make different Cells
• 2. They make only ½ Chromosome
• 4. They are Haploid instead of Diploid
• 3. Each germ cell only receives one copy of a chromosome

When the chromosomes are compacted to a more operable and identifiable form

One of the two identical copies of DNA making up a duplicated chromosome. When they separate, the strands are called sister chromatids.

• 1. Leptotene - condensation of chromatin, sister chromatids become connected by meiosis
• 2. Zygotene - Synapsis of homologous chromatids and it continues in pachytene.
• 3. Pachytene – Crossing-over of different chromatids
• 4. Diplotene - Condensation still occurs and homologous chrom starts to separate from each other (disjunction). Chiasmata appears
• 5. Diakinesis - Condensation of chrom. Nucleolus disappears and nuclear membrane disintegrates
• Lazy Zebras Play Dominoes Dominica

Rec8p

Diplotene stage one

35

When there is Monosomy = 23+22=45 chrom instead of the normal 46

In the male sperm

Polyploidy – multiples of haploid # of chrom (69, 92, etc)

46 4n DNA

• 1. Provides for constancy of chrom # for each generation
• 2. Allows independent assortment of maternal and paternal chromosomes
• 3. Allows for crossing over of genes – ‘ shuffling’ of genes
• 4.Disturbances can occur during this process for e.g. Nondisjunction

When the chromosome pairs don't seperate or don't completely seperate which can lead to TRIsomy, MONOsomy, ect.

• 2n = One pair of chromosomes
• This is how we are

46 = 2x23 (two of each chromosome)