Meiosis! Meiosis Gametogenesis Genetic Recombination Errors in Meiosis

Meiosis somatic cells (body cells) are diploid (2n) they contain two copies of each chromosome human somatic cells contain 46 chromosomes

Meiosis meiosis is a special type of cell division that only occurs in the reproductive organs meiosis results in the production of reproductive cells called gametes (sperm and eggs)

Meiosis gametes are haploid (n) they contain only one copy of each chromosome human gametes contain 23 chromosomes

Meiosis each human sperm or egg cell contains: 1 sex chromosome that determines the sex of the individual 22 autosomal chromosomes (autosomes) that determine everything else

Meiosis meiosis, involves the following phases: prophase I metaphase I anaphase I telophase I 5) prophase II 6) metaphase II 7) anaphase II 8) telophase II

Mitosis Meiosis I Meiosis II

To do now…. Meiosis Crash Course Meiosis Microviewers Mieosis Cards

Lesson Outline √ Meiosis Gametogenesis Genetic Recombination Errors in Meiosis

Gametogenesis the production of gametes Spermatogenesis occurs in male testis results in four non-identical sperm cells

Gametogenesis the production of gametes Oogenesis occurs in female ovaries results in the production of one viable egg and three non-viable eggs (polar bodies)

Gametogenesis the production of gametes Oogenesis polar bodies result from unequal division of cytoplasm (there is only enough cytoplasm to support one viable egg)

Lesson Outline √ √ Meiosis Gametogenesis Genetic Recombination Errors in Meiosis √

Genetic Recombination a rearrangement of genetic material during meiosis contributes to variation among generations (the variation can be a success or failure in the environment)

Genetic Recombination two examples of genetic recombination are: crossing over independent assortment

Genetic Recombination Crossing Over occurs during prophase I occurs between non-sister chromosomes in a tetrad genetic information is exchanged between chromosomes of paternal and maternal origin

Genetic Recombination Crossing Over usually occurs between 2 – 3 times per chromosome (depending on length)

Genetic Recombination Independent Assortment occurs during prophase I when chromosomes begin to line up, the chromosomes of maternal and paternal origin do not necessarily line up on the same side

Genetic Recombination Independent Assortment this separates the maternal and paternal chromosomes into different gametes

Lesson Outline √ √ √ Meiosis Gametogenesis Genetic Recombination Errors in Meiosis √ √

Errors in Meiosis errors in meiosis occur when the chromosomes fail to separate properly this is known as non-disjunction and results in gametes with more or less than the haploid number of chromosomes a

Errors in Meiosis Trisomy one extra chromosome

a a

Errors in Meiosis Polyploidy organisms with more than two complete sets of chromosomes (i.e. triploidy = 3n) common in plants and produces sterile offspring

Lesson Outline √ √ √ √ Meiosis Gametogenesis Genetic Recombination Errors in Meiosis Text Practice: reads page 113- 116 – highlight any vocab that is new – Compare: mitosis and meiosis √ √ √