DO NOW: What is better: sexual DO NOW: What is better: sexual or asexual reproduction? or asexual reproduction?
Mitosis Vs. MeiosisMitosis Vs. MeiosisThere are two types of cell
division that allow organisms to grow in size and in number.
Cell division: the separation of one cell into two
2 types of cell division: ◦Mitosis◦Meiosis
MitosisMitosisMitosis: makes
body cells and helps the organism to grow in size by producing TWO identical diploid cells
A type of asexual reproduction
Produces Diploid cells: a cell with two copies of each chromosome (2N)
1. 1. INTERPHASEINTERPHASE 3 Different Phases:◦G1 Phase: Period when cell growth and development occur
◦S Phase : DNA Replication / synthesis occurs
◦G2 Phase: Organelles needed for cell division are made (Centrioles and Spindle Fibers)
2. PROPHASE2. PROPHASEThe longest phaseChromosomes
appearCentrioles move to
opposite ends of the cell
Chromosomes attach to the spindle
Nucleolus and nuclear membrane breaks down
3. METAPHASE3. METAPHASE
Shortest phase of mitosis
Chromosomes line up at center of the cell
4. ANAPHASE4. ANAPHASECentromeres splitSister chromotids separate to form individual chromosomes
Anaphase ends when the movement of chromosomes stops
5. TELOPHASE5. TELOPHASEChromosomes uncoil into chromatin
Nuclear membrane reforms
Spindle breaks apart
MeiosisMeiosisMeiosis: makes
sex cells and helps an organism to reproduce by producing different haploid cellsHaploid: a cell with one copy of each chromosome (N)Male vs. Female: Meiosis produces 4 sperm cells in males and ONE egg cell in females
Why meiosis?Why meiosis?
Meiosis consists of two separate divisions, known as meiosis I and meiosis II.
Meiosis I begins with one diploid (2n) cell.
By the end of meiosis II, there are four haploid (n) cells.
These haploid cells are called sex cells— gametes.
Male gametes are called sperm.
Female gametes are called eggs.
When a sperm fertilizes an egg, the resulting zygote once again has the diploid number of chromosomes.
This pattern of reproduction, involving the production and subsequent fusion of haploid sex cells, is called sexual reproduction
Comparing Mitosis and MeiosisComparing Mitosis and Meiosis
Mitosis Meiosis
Number of cell divisions? 1 2
Exchange of genetic material? No Yes, crossing over!
Number of functioning cells produce?
2 4 sperm in males1 egg in females
Offspring are.. Identical to original
Highly variable and diverse, contain half of the genetic information of the original
Purpose? Growth or replacement of body cells
Combine to form the zygote for reproduction
Pros and ConsPros and ConsMitosis Meiosis
Positives Repair old or damaged cells
Make exact copies
Varied offspring
Species is more stable
Negatives Organisms are all the same so one disease can wipe out an entire population
Requires 2 parents
More time consuming