mitosis/cell division review
DESCRIPTION
Mitosis/Cell Division Review. A. B. C. D. E. Meiosis . Produces gametes or sex cells (sperm and egg cells) Occurs ONLY in the reproductive organs. Products of Meiosis = 4 new cells. AND. Divides the chromosome number in half. For Example: . Parent Cell. 4 daughter cells. - PowerPoint PPT PresentationTRANSCRIPT
Mitosis/Cell Division Review
B
C
D
E
A
Meiosis -Produces gametes or sex cells (sperm and egg cells) -Occurs ONLY in the reproductive organs
Products of Meiosis = 4 new cells
ANDDivides the chromosome
number in half
For Example:
Parent Cell
4 daughter cells
2 Sets of Divisions
1st division is exactly like mitosis except sister chromatids stay together
Before the 1st division takes place DNA MUST replicate
Prophase I• Chromosomes condense
• Homologous chromosomes pair together
• Crossing over occurs
Crossing Over
Metaphase I• Homologous pairs are moved to the equator (middle) of the cell
Anaphase I • Homologous pairs separate
•Chromatids remain together
•Genetic material has been recombined
Telophase I
•Chromosomes gather at poles•Cytoplasm divides
2nd DIVISION BEGINS
DNA replication DOES NOT
occur
Prophase 2• New spindles form around chromosomes
• Crossing over – does not occur!
Metaphase 2• Chromosomes align along with equator (middle) of the cells
Anaphase 2
• Sister chromatids (now called chromosomes) divide and move to opposite poles
Telophase 2•Chromosomes gather at the poles
•Nuclear envelope forms and cytoplasm divides
4 new daughter cells, each genetically DIFFERENT, are formed and are all haploid
Sexual Reproduction• Haploid cells join to make diploid cells
• Increase in genetic variation
• Leads to change or evolution
Females: meiosis occurs before birthEach month, one egg is matured
and released for possible fertilization
Males: meiosis begins at puberty and continues until death
Asexual Reproduction•Single parents pass genes to offspring
Clones
Prokaryotes, yeast, hydra
Faster to produce offspring, but no genetic variation
GENETIC VARIATION • The chromosome a gamete will receive depends on the way it lines up at the equator
Independent
assortment
The Importance• Lead to the evolution of a species• Increase survival
CANCER• Cells have checkpoints to determine if they are healthy enough to divide
• If those checkpoints are faulty, cells can divide and grow uncontrollable – can form a tumor and lead to cancer
What’s the problem with more cells?
1.) Steal nutrients from healthy cells which eventually die
2.) Can travel from their original location
METASTASIZE
Causes of Cancer• Exposure to chemicals or toxins
• Radiation
• Viruses
• Your Own Genetics