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DO NOW – 2/15/08
• Complete the two Dihybrid crosses on eye color and widow’s peak.
• Report the phenotypic ratios in your DO NOW.
The Cell and Inheritance
How are genes passed?
– An EGG is the female sex cell– SPERM is the male sex cell
• These are GAMETES: a mature sexual reproductive cell
• What is a somatic cell?
What is different about our cells?
• Somatic cells of humans have 46 chromosomes.
• Human sex cells have 23 chromosomes. – The sex cells have exactly half the
number of chromosomes found in body cells.
• When a sperm cell joined with an egg cell, the fertilized egg that forms has 46 chromosomes.
• The 46 chromosomes are in 23 pairs. Each pair has 1 chromosome from the mother and 1 chromosome from the father.
MEIOSIS• MEIOSIS is the
process by which the number of chromosomes is reduced by half to form gametes.
• The new gametes
that are formed have half as many chromosomes as the somatic cells.
What do we like to do?…REVIEW!!
• The somatic cells of dogs have 78 chromosomes. - How many chromosomes do their gametes have? •39
•The sex cells of silk worms have 28 chromosomes.
–How many chromosomes do their body cells have?
•56