meiosis

MITOSIS

*takes place in somatic cells *produces 2 identical diploid(2n) daughter cells *growth of organism *tissue maintenance and repair

Telophase

- Nuclear envelope forms - Daughter cells contain one chromosome from each homologous pair - Each chromosome is still a sister chromatid

Independent Assortment

-There are 8 possible arrangements that could take place during metaphase I

Cell Cycle begins with?

Interphase

Cell Cycle for eggs and sperm:

Interphase Meiosis I Interkinesis Meiosis II Cytokinesis

Meiosis I and II phases?

Meiosis 1: Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Meiosis 2: Prophase 2 Metaphase 2 Anaphase 2 Telophase 2

Homlogous chromosomes

Member of a pair of chromosomes that are alike and come together in synapsis during prophase of the first meiotic division

Oogenesis Where does it take place? etc..

Ovaries. Although cell division takes place, only one mature egg is produced. After meiosis I, one cell receives most of the cytoplam. The cell is the functional egg The other cell is a nonfunctional polar body.

Synapsis

Pairing of homologous chromosomes during meiosis I

In humans, meiosis begins with what?

Primary spermatocytes & oocytes that are diploid (2n)

Result of Meiosis

Produces sperm and eggs (gametes) 4 Haploid (n) daughter cells with genetic variation

oogenesis

Production of eggs in females by the process of meiosis and maturation

spermatogenesis

Production of sperm in meiosis by the process of meiosis and maturation

Anaphase II

Sister chromatids seperate & becomes daughter chromosomes

embryo

Stage of multi cellular organism that develops from a zygote before it becomes free-living; in seed plants, the embryo is a part of the seed.

Oogenesis...

The cell undergoes prophase II and will not continue meiosis unless the egg is fertilized. If the egg is fertilized, metaphase II takes place and the polar body divides again At the completion of oogenesis, there is one fertilized egg & 3 polar bodies. Fertilized egg is called a zygote Called an embryo after the 2nd week of development If the egg is not fertilized, it will break down & be released during menstruation

Genetic Diversity

Three contributions: Crossing over during prophase I Independent assortment during metaphase Random meeting of a sperm & egg at fertilization

Do Meiosis I and II go through the same phases as mitosis with some variation? If so, what are the phases?

Yes, the genetic variation in Meiosis is introduced at three different times: fertilization- the random act of an egg meeting a sperm F.R.E.M.S prophase I- Crossing Over P.C.S metaphase I- Independent assortment M.I.A

polar body

a small cell containing little cytoplasm that is produced along with the oocyte and later discarded

Bivalent

each having a sister chromatid that are joined by a nucleoprotein lattice during meiosis; also called a tetroid

Crossing Over

it is estimated that an average of 2-3 cross-overs per human chromosome

asexual reproduction

reproduction that only involves one parent and does not involve gametes

Spermatogenisis, when does it begin? where does it take place? What is produced after undergoing meiosis?

sexual maturity. testes. 4 mature sperms

Independent assortment

Alleles or unlinked genes segregate independently of each other during meiosis so that the gametes contain all possible combinations of alleles

Human Karyotype

Alternate forms of genes called alleles - The allele from mom may code for short fingers - The allele from dad may code for long fingers

Alleles

Alternative form of a gene- alleles occur at the same locus on homologous chromosomes

secondary oocyte

An oocyte in which the first meiotic division is completed. The second meiotic division usually stops short of completion unless fertilization occurs.

Prophase II

Begins with two cells that were produced during meiosis I. The two cells have one chromosome (sister chromatid) from each homologous pair

Telophase II

Cells begin to seperate Nuclear envelope forms

Interphase

Cells grow,organelles increase & DNA replicates - Replicated= duplicated Replicated chromosomes (DNA) contain sister chromatids connected at the centromere. CG, OJ, DR, RC: cells grow, organelles increase, DNA replicates, Replicated centromere

In Prophase I, what is contributed by the father and one by the mother? What do these regions code for?

Chromosomes - same traits, finger length, hair color,eye color, height, etc.

Metaphase II

Chromosomes line up along the center of the cells

After independent assortment?

Chromosomes seperate and will be distributed into different cells

Prophase I

Crossing over takes place Non sister chromatids exchange genetical material - chromatids from mom cross over with chromatids from dad

Interkinesis

Cytoplasm seperates RESULT= 2 CELLS !

Zygote

Diploid cell formed by the union of 2 gametes; the product of fertilization.

Cytokinesis

Each of the two cells from meiosis I divide to form four haploid cells (n)

Define gametes

Eggs and sperm

Meiosis produces?

Eggs and sperm cells with 23 chromosomes.

Crossing over

Exchange of segments between non sister chromatids of a bivalent during meiosis

Gametes

Haploid sex cell; egg and sperm

Anaphase I

Homologous chromosomes seperate and move toward poles * sister chromatids remain together

Metaphase I

Homologous pairs of chromosomes line up in the center of the cell. Spindle fibers are in place (independent assortment) The random arrangement contributed to genetic variation

oocyte

Immature eggs that is undergoing meiosis; upon completion of meiosis, the oocyte becomes an egg

What is a haploid number?

A cell with 23 chromosomes(n)

What is a diploid number?

A cell with 46 chromosomes (2n)

The eggs and sperm in humans each contribute how many chromosomes during what? Which equals a total of how many chromosomes?

23 chromosomes during fertilization, total=46 -n+n=2n

During Meiosis one diploid cell (2n) divides into what?

4 genetically different daughter cells (haploid - n)