BIOL140 Lecture Notes - Lecture 6: Inta, Cytokinesis, Dna Replication
10 views2 pages
BIO Lecture #6
September 29th, 2015
Cells in human body have 46 Chromosomes
○
Diploid- 2n
○
Body Cells
Gametes have 23 chromosomes
○
Gametes are reproductive cells
○
Reproductive Cells
Increases the chance of survival in a changing environment
Increases Genetic Diversity
○
Meiosis is the only kind of cell division that produces gametes
○
Why did Miosis evolve when sexual reproduction evolved?
Chromosome Number and Cell Division
Egg + Sperm ➡Zygote
Without reduction--- 46 + 46 ➡ 92 ✖
With Reduction--- 23 + 23 ➡ 46 ✔
2n➡n
Reduces Chromosome number
○
Reduction Division
Separates Chromosome pairs
1st Division
○
Chromosomes are copied before Meiosis
Separates chromatids
2nd Division
○
Involves two Divisions
Copy chromosomes ➡increase # of gametes➡Increase chance of successful reproduction
○
DNA Replication occurs prior to Meiosis
Meiosis
Cell gets ready for division
Synapsis-Homologous Chromosomes pair up
i.
Unique combinations of chromosomes in each gamete
>
Produces new combination of genes
Crossing Over- non- sister chromatids exchange pieces of DNA
ii.
Prophase 1
1.
Homologous Chromosomes line up along Metaphase plate
Metaphase I
2.
Diploid ➡Haploid
Separation of Homologous chromosomes
Anaphase I
3.
Nuclear Membrane is rebuilt
Telophase I
4.
Meiosis I
A)
Parent cell divides into two daughter cells
○
Cytokinesis I (Interkinesis)
B)
Similar to Mitosis
○
Seperation of chromatids
○
Meiosis II
C)
Won't work because it results in too many
Chromosome = Different species
Situation #1
(No Copying)
Crossing Over
Metaphase I
Male Gametes
Creation of Sperm
Spermatogenesis
a)
Gamete Production
Meiosis I
Meiosis II
Maturing
Streamlining
Develop Motor & Tail
Lose Organelles
Sperm
Oogenesis
b)
Situation #2
(copying)
Homologous Pair
Meiosis
Lecture Six and Seven
October 4, 2015
5:28 AM
BIO 140 Page 1