Transcript The Cell and Inheritance

The Cell and Inheritance
• Objectives:
• Describe chromosomes and their role in
inheritance.
• Identify and describe the events that occur
during meiosis.
Vocabulary
• Sperm
• Egg
• Meiosis
• Questions:
• How many parent cells and how many
daughter cells in Meiosis?
• How are mitosis and meiosis different in
terms of types of cells?
Discovery in area of sex cells
 Sutton 1903
 Studied movement of chromosomes as
sex cells developed in grasshoppers.
egg- female sex cell
sperm- male sex cell
 Hypothesized-chromosomes were key to
understanding how offspring come to have
similar traits to parents.
MEIOSIS
Chromosomes in
body cells of
grasshoppers
24
12 male
chromosomes
Chromosomes in sex
cells of grasshoppers
12
12 female
chromosomes
24 chromosomes
ll ll ll ll ll ll ll ll ll ll ll ll ll
12 pair
One each from male
One each from female
‘Chromosome Theory of
Inheritance’
• Chromosomes carry genes from one generation to
the next.
• Question: How does the number of
chromosomes in a grasshopper sex cell
compare to the number in it’s body cells?
• Answer: Sex cells have exactly half the number.
• Question: How do they end up with half?
• Answer: Meiosis
Humans = 23 pairs
Meiosis and Punnett Squares
Male
Parent cell
XY
X
X
Female
parent cell
XX
X
Y
XX
XX
XY
XY
How Meiosis Works:
McGraw-Hill: Animated presentation
• Meiosis – The Continuation of Life ( 12
min. video clip)
• Chromosome: The self-replicating genetic
structure of cells containing the cellular DNA
• Gene: The fundamental physical and functional
unit of heredity
• DNA (deoxyribonucleic acid):
The molecule that encodes genetic information.
DNA is in genes, genes are part of chromosomes
Different placement of genes on
a chromosome
Cell & Inheritance Quiz
Vocabulary:
1. a female sex cell
2. The process that occurs in sex cells by which
the number of chromosomes is reduced by half.
3. a male sex cell
Questions:
4.How many parent cells and how many daughter
cells in Meiosis?
5.How are mitosis and meiosis different in terms of
types of cells?
Answers
2 pts. each
10 possible
1. egg
2. meiosis
3. sperm
4. one parent and 4 daughter cells in
Meiosis
5. mitosis-growth and repair cells like skin.
meiosis-sex cells, egg and sperm.