Download Notes 4-3

7th Grade Life Science
Mr. Fisk
Chapter 4 - Genetics: The Science of Heredity
Engage – How are sperm and eggs made?
Objectives:
1. Describe the role chromosomes play in
inheritance.
2. Identify the events that occur during meiosis.
3. Explain the relationship between
chromosomes and genes.
4-3 The Cell and Inheritance
A. Chromosomes & Inheritance
1. In grasshoppers Sutton found
Body Cells = 24 chromosomes
Sex Cells = 12 chromosomes
2. Chromosomes Pairs – In grasshoppers
24 chromosomes = 12 pairs
1 from the sperm
1 from the egg
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7th Grade Life Science
Mr. Fisk
3. Genes on Chromosomes – Genes are
carried from parents to the offspring on
chromosomes.
B. Meiosis – process by which the number of
chromosomes is reduced by half to form Sex Cells
(Egg & Sperm)
1. Chromosomes pairs separate and are
distributed to 2 different cells.
2. Meiosis & Punnett Square
 Punnett square shows the events that
occur in meiosis.
Tt – Male Parent
Female
Parents Tt
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T
t
T
t
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7th Grade Life Science
Mr. Fisk
C. A Lineup of Genes
1. Human body 23 chromosomes pairs or
46 Chromosomes.
2. Chromosomes are made up of many
genes joined together like beads on a
string.
A
a
b
C
D
e
F
G
H
B
C
d
e
F
g
H
I
j
K
l
M
i
J
K
L
m
3. Your cells each contain 35,000 genes –
Each gene controls a trait..
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