Diploid Vs. Haploid• Diploid - two sets of chromosomesDiploid - two sets of chromosomes• Haploid - one set of chromosomesHaploid - one set of chromosomes• Diploid cells (2n or 2 sets of Diploid cells (2n or 2 sets of
chromosomes) are made into chromosomes) are made into haploid (1n or 1 set haploid (1n or 1 set chromosomes) during meiosischromosomes) during meiosis
• Examples of diploid cells: almost all your cells! Most plant & animal cells are diploid (2n)
• Examples of haploid cells: gametes, egg & sperm (n)
How Many Homologous How Many Homologous Chromosomes? Chromosomes?
• Homologous pairs carry genes controlling the same inherited traits.
• Humans have 23 pairs of homologous homologous chromosomes.chromosomes.a. 22 pairs of autosomesautosomesb. 1 pair of sex sex chromosomeschromosomes
Homologous Chromosomes• Each organism that is produced via sexual
reproduction has 2 copies of autosomes, one comes from each parent
Homologous chromosomes (Homo=same) chromosomes that are the same size & shape; carry genes for the same traits
Meiosis• Meiosis: the form of cell divisioncell division where
sex cells are produced (gametesgametes). • Purpose: to produce sex cells (gametes) for
sexual reproduction
• Sex cells (sperm or egg) have halfhalf the # of chromosomes chromosomes as a normal body cell
FertilizationFertilization
• The fusion of a spermsperm and eggegg to form a zygotezygote.
n= 23egg
sperm n = 23 2n = 46
zygote
Question:Question:• A cell containing 20 chromosomes20 chromosomes (diploid)(diploid) at
the beginning of meiosis would, at its completion, produce cells containing how many chromosomeschromosomes?
• ANSWER = 10 chromosomes (haploid)
• Animation http://www.johnkyrk.com/mitosis.html
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