meiosis cornell notes. meiosis animation video pmp0u0hoa pmp0u0hoa
TRANSCRIPT
• Meiosis Cornell notes
• Meiosis animation video
• https://www.youtube.com/watch?v=rqPMp0U0HOA
• Each one of us have characteristics passed on to us from our parents
• Each characteristics we have is called a trait
• The DNA on the chromosomes are arranged in segments called genes
• Each chromosome consist of hundreds of genes
SEXUAL REPRODUCTION
Sex cells formed by meiosis
Requires 2 parents
Offspring not identical
A kind of cell division that results in gametes (sex cells) withhalf the number of chromosomes
In order to maintain the same chromosomes # from generation to generation, an organism produces gametes (sex cells) that have half the # of chromosomes
Haploid means HALF, as in the number of chromosomes,written as n
Meiosis
Gametes
Haploid
Homologous Chromosomes
* Human body cells have 46 chromosomes
* Human body cells have 23 homologous pairs
Meiosis and Fertilization
One haploid gamete combines with another haploid gamete.As a result of fertilization, the cell now will contain a total of 2n chromosomes
Fertilization
The union of an egg and a sperm
n
n 2n
Homologous chromosomes
Phases of Meiosis (2 cell divisions )
• Interphase
–Chromosomes replicate
–Chromatin condenses
Phases of Meiosis (2 Cell divisions – Meiosis I & Meiosis II)
MEIOSIS I
Prophase I
Pairing of homologous chromosomes, crossing over occurs, nuclear envelope breaks down, and spindles form
Metaphase I
Spindle fibers attach to homologous chromosomes (pairs) and line up in the middle of the cell.
Anaphase I
The fibers pull the homologous chromosomes apart. Chromosomes move toward opposite sidesof the cell.
Telophase I
During Telophase I and cytokinesis, the spindles break down, chromosomesuncoil and form two new nuclei, the cell divides (2 daughter cells)
**** The Chromosome number is reduced to half during Meiosis I forming haploid (n) daughter cells
MEIOSIS II
Prophase II
Chromosomes condense, spindle fibers form in each new cell, Spindle fibers attach to chromosomes
Metaphase II
Chromosomes line up in the middle of the cell
Anaphase II
Sister chromatids separate and move towards opposite sides of the cell
Telophase II
Cells divide, resulting in 4 haploid cells – gametes (sex cells)
MeiosisMeiosis
Parent cell – chromosome pair
Chromosomes copied
1st division - pairs split
2nd division – produces 4 gamete cells with ½ the original no. of chromosomes
• Summary • 3 to 4 sentences of meiosis notes
15
Mitosis, Meiosis, or Neither
Number 1 - 6
17
How this sperm cell was created
18
DNA replication happens before this process.DNA replication happens before this process.
19
When the sperm actually meets the egg.
20
I’m a single celled
paramecium. Time to
reproduce!
21
DNA replication happens before this process.DNA replication happens before this process.
22
ANSWERS!
Number 1 - 6
24
How this sperm cell was created
25
DNA replication happens before this process.DNA replication happens before this process.
26
When the sperm actually meets the egg.
27
I’m a single celled
paramecium. Time to
reproduce!
28
DNA replication happens before this process.DNA replication happens before this process.
29