Meiosis
Name _____________________________
Date _______________ Period ________
6.1 – Chromosomes & Meiosis
Key Concept: Gametes have half the number of chromosomes that body cells have.
You have somatic (body) cells and gametes (sperm or egg).
-Somatic Cells
-Are __________________________________
-Make up ____________________________________________________
-___________________________ on to children
-Gametes
-Are __________________________________
-___________________________ on to children
You cells have autosomes and sex chromosomes.
-Somatic cells have ___________________ of chromosomes (46 total)
Somatic cells are diploid; gametes are haploid.
Diploid (_____)
• Has __________________ of each
chromosome (1 from ________________
& 1 from _________________)
• _____ autosomes, _____ sex
chromosomes
• __________________________ are diploid
• Produced by ___________________
Haploid (_____)
• Has ______________ of each chromosome
• _____ autosomes, _____ sex
chromosome
• ________________ are haploid
• Produced by __________________
Mitosis vs. Meiosis
-Chromosome number must be maintained in animals.
-Many plants have more than two copies of each chromosome (can be tetraploid [4n] or hexaploid [6n])
-Mitosis and meiosis are types of nuclear division that make different types of cells.
6.2 – Process of Meiosis
Key Concept: During meiosis, diploid cells undergo two cell divisions that result in haploid cells.
Cells go through two rounds of division in meiosis.
-Meiosis _______________________________________ and creates ____________________________.
-Homologous chromosomes (sometimes called ______________________________)
-_____________ of chromosomes
-Inherit one from each _______________
-Carry same genes but code for different traits (different versions of the genes)
-Separate during __________________________
-Sister chromatids
-Duplicates of ________________________
-Each __________ of a duplicated chromosome
-Attached together at the __________________________
-Separate in _______________________________
Mitosis vs. Meiosis
Mitosis
• One cell division
• Homologous chromosomes do not pair up
• Results in diploid cells
• Daughter cells are identical to parent cell
Meiosis
• Two cell divisions
• Homologous chromosomes pair up (Metaphase I)
• Results in haploid cells
• Daughter cells are unique
Haploid cells develop into mature gametes.
-Gametogenesis differs between males and females.
-Sperm (______________________)
-Become streamlined and motile (able to move)
-Primary contribution to embryo is DNA only
-Males produce over 250 million sperm per day
-Egg (_______________________)
-Contribute _________________________________________ to the embryo
-During meiosis, the egg gets most of the contents; the other 3 cells become polar bodies
-Females produce a few hundred eggs over a lifetime
6.6 – Meiosis & Genetic Variation
Key Concept: Independent assortment and crossing over during meiosis result in genetic diversity.
Sexual reproduction creates unique combinations of genes.
-Fertilization
-________________
-Increases unique ____________________________________
-In humans, the chance of getting any one combination of chromosomes from any one set of parents is
one out of 223 x 223 (which is one out of over __________________________ combinations)
-Independent assortment of chromosomes
-Homologous chromosomes _________________________________ along the cell equator
-Increases the number of unique combinations of genes
-In human cells, about 223 (8 million) different combinations could result
-Crossing over
-________________________________________________________________________________
-Increases genetic diversity
-Occurs during Prophase I of Meiosis I
-Results in new combinations of genes (chromosomes have a combination of genes from each parent)
Genetic linkage
-Chromosomes contain many genes.
-The ____________________________ two genes are located on a chromosome, the
_____________________________ they are to be separated by crossing over
-Genetic linkage: __________________________________________________________
_______________________________________________________________________