Post on 17-Dec-2015
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How does genetic variation occur? EQ: How do parents with the same genes make offspring that are so different?
• Meiosis: the process by which the number of chromosomes per cell is cut in half the the separation of homologous chromosomes in a diploid cell
How does genetic variation occur?
Meiosis
Question: The average human has 23 pair of chromosomes. How many pairs will a cell have after chromosome duplication?
Meiosis
Question: The average human has 23 pair of chromosomes. How many pairs will a cell have after chromosome duplication? 46 pairs
Meiosis
Question: The average Time Lord has 68 pair of chromosomes. How many pairs will a cell have after chromosome duplication?
Meiosis
• Step 2: Crossing Over– Homologous chromosomes pair together and
gene alleles are able to switch with the neighboring chromosome.
Meiosis • Step 2: Crossing Over– Homologous: chromosomes with same genes, one
from each parent– Alleles: one of a number of different forms of a gene
Meiosis • Step 3: Meiosis I– Homologous chromosomes are separated into 2
sister cellsStatus Check: How many chromosomes at this stage for the average human? Time lord?
Meiosis • Step 4: Meiosis II– Homologous chromosome pairs are separated into
2 sister cells with half the amount of chromosome as the original cell.
Status Check: How many chromosomes at this stage for the average human? Time lord?
Meiosis • Step 4: Meiosis II– Creates 4 genetically different haploid cells– Genes are randomly separated into the 4 different
cell which is the Principle of Independent Assortment
Meiosis • Step 4: Meiosis II– Haploid cells: (Greek haplous means single)
contain ½ the amount of chromosomes– Diploid cells: (diplo- means double) contains both
sets of homologous chromosomes