Post on 19-Jun-2015
Meiosis & Reproduction
Asexual Reproduction
• Identical offspring (clones)
• Mitosis
• Different kinds– Binary fission– Budding– Fragmentation– Regeneration
Sexual Reproduction
• Two parents
• Genetic variation
• Haploid gametes
• Unique offspring– Similar to parents– Similar to each other
Genetic VariationFor humans - 23 pairs of chromosomes:
• Independent Assortment – 50/50 chance that gamete gets maternal/ paternal homologous chromosome– # of possible gametes = 223
– >8 million possible gamete combinations
• Random Fertilization– (8 million)(8 million) = 64 trillion possible offspring
• Crossing over – increases genetic variation even more
Haploid vs. Diploid
HAPLOID• 1n
• One copy of each chromosome
DIPLOID• 2n
• Two copies of each chromosome
• Homologous chromosomes
Karyotyping
Human Female Karyotype
Human Male Karyotype
Life Cycles
Overview of Meiosis
• Diploid parent cell divides twice to make haploid gametes
• Homologous chromosomes
• Sister chromatids
Meiosis I
Meiosis II
Mitosis vs. Meiosis
Gamete Possibilities(due to Independent Assortment)
Crossing Over
• Increases genetic variation
• Synapsis• Tetrad• Chiasma
• Happens during Prophase I
Homologous chromosomes move toward opposite poles of a dividing cell during
A. Mitosis
B. Meiosis I
C. Meiosis II
D. Fertilization
E. Binary fission
If the DNA content of a diploid cell in the G1 phase is x, then the DNA content of the cell at metaphase I of meiosis would be
A. 0.25x
B. 0.5x
C. x
D. 2x
E. 4x
For the same cell, the DNA content at metaphase II of meiosis would be
A. 0.25x
B. 0.5x
C. x
D. 2x
E. 4x
How many different combinations of chromosomes can be packaged in gametes by an organism with a diploid number of 8 (2n = 8)?
A. 2
B. 4
C. 8
D. 16
E. 32