Chapter 9

Meiosis Stages

Interphase (G1,S,G2) Cell Division: Meiosis I: Prophase, Metaphase, Anaphase, Telophase, Cytokinesis Meiosis II: Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

Meiosis II: Anaphase II

-Centermeres split as sister carotids separate to opposite poles

Meiosis I: Telophase 1 + Cytokinesis

-Chromosomes are enclosed in two nuclei -Chromsomes decondense -Finally are separated and will continue to Meiosis II

Meiosis I: Prophase I

-Chromsomes condense -Recombination between homologous chromosomes -Centrosomes move to opposite poles -Nuclear disintegrates

Meiosis I: Metaphase I

-Homologous chromosomes pairs align as pairs along the center

Meiosis I: Anaphase I

-Homologous chromosomes pairs are pulled apart (sis with be together)

Meiosis II: Telophase II and Cytokinesis

-Nuclear envelopes form -Chromosomes decondense -Spindles disappear -Cytokinesis occurs, cell divides -Now there are four haploid daughter cells with non-duplicated chromosomes

What are the products of mitosis? Meiosis? Compare number of products & number of chromosomes per product.

Mitosis: 2 identical daughter cells each with 46 chromosomes Meiosis: 4 non-identical daughter cells with 23 chromosomes each

What is polyploidy? How is it different than aneuploidy? How do we represent polyploidy?

Polyploidy: an extra complete set of chromosomes so (3N or 4N)

What is trisomy and how is it caused? What is monosomy and how is it caused? How do we represent trisomy? How do we represent monosomy? Could you look at a karyotype and determine if that individual has a trisomic disorder or monosomic disorder?

Trisomy: (n-1) cells contain an extra chromosome Monosomy: (n+2) cells are missing a chromosome

Meiosis II: Metaphase II

-chromosomes align in center

How does diploid/haploid relate to mitosis & meiosis?

- Sexually reproductive orgainsms are diploid (meiosis) *also perform mitosis -Asexually reproductive organisms are haploid (mitosis)

Walk me through the human life cycle: when are cells haploid? When are cells diploid? When does mitosis occur? When does meiosis occur?

1. Mom and Dad are diploid organisms that each have 23 pairs (46 chromo) of chromosomes 2. Mom and Dad go through meiosis individually. Mom creates germ cell: egg cell. Egg cell is haploid with only 23 chromosomes. Dad will undergo meiosis to create germ cell: sperm. Sperm cell is haploid and has 23 chromosomes. 3. Mom and Dad germ cells come together during sex and egg is fertilized by sperm cell. 4. This lead to a zygote that is now a diploid because mom and dads germ cells combined together to give 46 chromosomes to zygote. 5. Zygote will undergo mitosis as it develops into a baby which is also a diploid organism (46 chromosomes) 6. Once baby is born it'll always be diploid except for its germ cell. The baby will undergo mitosis its entire life for development and growth and repairing.

How does the process of fertilization contribute to genetic diversity?

Any sperm can fuse with any egg. There are 2^23 ways chromosomes can be sorted once fertilized

What is crossing over/recombination? When does it occur? How could you draw it? How does it relate to genetic diversity?

Crossing over is the process in which two homologous chromosomes exchange genetic material between homologous chromosomes. Occurs in Prophase I

What does diploid mean? How do we represent diploid? What types of cells are diploid?

Diploid: are chromosomes that come in pairs. One is inherited by mother and other by father. Each diploid human cell has 46 chromosomes -2N is how to represent diploid -Somatic cells like muscle and skin cells

What does haploid mean? How do we represent haploid? What types of cells are haploid?

Haploid cells: they contain only one full set of genetic information instead of two sets like a diploid. -Haploid cells are represented with (N) -They are germ cells: aka sperm and egg cells

Compare and contrast mitosis & meiosis. Draw them side by side with labels. Make sure to include # of chromosomes and # of sister chromatids at each step. How are they similar? How are they different?

Mitosis: somatic cells produced, one cell division Meiosis: gametes are produced, 2 cell divisons -Interphase: both have 46 chromosomes -Prophase: 46 chromosomes 92 sister chromatids are same -Metaphase: 46 chromo and 92 sis chromo are same -Anaphase: 92 daughter chromosomes and 0 sis chromatids for Mitosis. 46 chromosomes and 92 sister chromatids for meiosis. -Telophase: 92 daughter chromosomes and 0 sister chromatids for mitosis. Meiosis has 46 chromosomes and 92 sister chromatids. Cytogenesis: 46 daughter chromosomes for each daughter cell for mitosis. For meiosis each daughter cell 23 chromosomes and 46 sister chromatids. Which will continue to undergo another cell division.

What is nondisjunction? What are the consequences of nondisjunction? How would you recognize that nondisjunction has occurred? How would you recognize that an What is aneuploidy? organism has aneuploidy?

Nondisjunction: occurs when chromosomes fail to separate at either anaphase I or anaphase II. Consequence can lead to miscarriages or in some syndromes Aneuploidy: extra or missing chromosomes ex: Trisomy 21: Down syndrome

Meiosis II: Prophase II

-A spindle forms -Nuclei envelope break up

Explain the differences between identical twins and fraternal twins.

Identical twins: (Monozygotic) I egg and I sperm. I zygote broke into two embryos Fraternal twins:(dizygotic) two sperm cells fertilized two separate egg cells

What is independent assortment? When does it occur? How could you draw it? How does it relate to genetic diversity?

Random alignment of chromosomes. Which occurs in Metaphase I.