1. Asexual Reproduction Sexual Reproduction
Binary Fission is a form of asexual reproduction
Production of offspring by a single parent
some eukaryotes reproduce asexually
They do this by mitosis
Sexual Reproduction
Multicellular organisms usually reproduce sexually.
Cells from two parents join to form a NEW individual
offspring produced sexually are genetically different from either parent
meiosis

3. Gregor Mendel 1822 Austrian monk University of Vienna
In charge of the Garden

4. What Gregor Mendel Knew…
Each organism must inherit a single copy of every gene from each of its “parents”
Each of the organisms gametes must contain just one set genes
When gametes are formed, there must be a process that separates the 2 sets of genes so each gamete gets one set

5. Meiosis
Process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell

6. Karyotype
A photograph of a person's chromosomes, arranged according to size

10. Chromosome Number Homologous chromosomes Fruit fly has 8 chromosomes
Chromosome that has a corresponding chromosome from the opposite-sex parent
Similar in size, shape, and genetic material
Fruit fly has 8 chromosomes
4 from mom
4 from dad

12. Diploid
Di= two sets
Cell that contains both sets of homologus chromosomes
Cell contains
2 complete sets of chromosome
2 complete sets of genes
Number of chromosomes in diploid cell represented by 2N
For Drosophilia (fruit fly) 2N=8
Mendel said:
Each adult cell contains two copies of each gene

13. Haploid Means “one set”
Refers to cells that contain only one set of chromosomes
Gametes (sex cells)
Represented by N
Drosophilia fruit fly
N=4

14. How are haploid (N) gametes made from diploid (2N) cells?

15. Meiosis 2 distinct stages Meiosis I Meiosis II
A diploid cell enters here
Meiosis II
At the end of this, the diploid cell that entered meiosis has become 4 haploid cells
When sex cells form, the chromosomes are copied once. The nucleus then divides twice (meiosis I and meiosis II). The four cells that result have half as many chromosomes as a normal body cell.

18. Meiosis I
Before meiosis 1, each chromosome is replicated (interphase of the cell cycle).
Tetrads line up like the sister chromatids did in mitosis
What happened in mitosis?
PMAT
Tetrad
STRUCTURE MADE WHEN EACH CHROMOSOME PAIRS UP WITH ITS HOMOLOGOUS CHROMOSOME
4 CHROMATIDS IN A TETRAD

19. Prophase I Homologous chromosomes pair up (SYNAPSIS) , makes a tetrad
As they pair up in tetrads, chromosomes exchange portions of their chromatids in the process …. CROSSING OVER
- First way genetic variation in gametes is achieved

20. Crossing Over
Part of a chromatid on one chromosome breaks off and switches position with the matching portion on a chromatid of the homologous chromosome
increases the # of genetic combinations in offspring

22. Metaphase I
Homologous pairs line up along the center of the cell in a random fashion= independent assortment
Another form of genetic variation
When the cell divides, each daughter cell will receive a mix of chromosomes that differ than that of the original cell

23. Anaphase I
spindle fibers separate the paired homologous chromosomes and pull them toward opposite poles of the cell.
Telophase I
Cell divides to produce two daughter cells
each with a complete set of chromosomes

25. Now what do we have? 2 new daughter cells
Are they identical to the parents? No
Let’s say the parent started with 8 chromosomes
Each daughter cell has 8 chromosomes but they are different because of crossing- over
Each daughter cell has a set of chromosomes and alleles different from each other and different from the parent diploid cell
moving on to Meiosis II

26. Prophase II Meiosis I resulted in 2 “seemingly” diploid cells
Remember they are genetically different b/c of crossing over in prophase I
We still need to cut this number in half to reach our goal of 4 haploid cells
Meiosis II doesn’t replicate the chromosomes again
Does not form tetrads because the homologs were already seperated during meiosis I

27. Metaphase II Anaphase II Telophase II Chromosomes line up in middle
Sister chromatids separate and move to opposite poles
Telophase II
Meiosis II results in 4 haploid (N) daughter cells

30. Gamete Formation
Male
Haploid gametes produced by meiosis are called spermatozoa
Spermatogenesis begins at puberty and continues throughout one’s life
Under hormone and environmental control
Female
Haploid gamete produced by meiosis is called an oocyte
Cell divisions at the end of meiosis one and two are uneven so one cell gets most of the cytoplasm (the EGG) and the other three are called polar bodies (don’t participate in reproduction)
IMPORTANT!
Female gametes are stuck in Prophase 1 until puberty
Complete Meiosis 1 every month and the secondary is released from ovary
Female gametes only reach and complete meiosis 2 if they are fertilized