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Chromosomes,
DNA, and Genes
EQ: Can I describe the
relationship among genes,
chromosomes, and inherited traits?
0707.4.3
What is a chromosome?
• One of the
structures in the
nucleus that is
made up of DNA
and protein
• Carries hereditary
information in the
form of genes
• Humans have 23 pairs of chromosomes,
46 total.
• You received 23 chromosomes from
your father, and the other 23
chromosomes from your mother.
CHROMOSOMES
Sex Chromosomes
• 22 of our pairs of chromosomes appear
identical, but the other two chromosomes
are called sex chromosomes- X and Y.
• Females=
2 X Chromosomes
• Males= 1 X and 1 Y
Chromosome
What is DNA?
• A molecule that is
present in all living
cells and that
contains the
information that
determines traits
that a living thing
inherits and needs
to live.
DNA
Each cell in your body contains
about 6 feet of DNA thread, for
a total of about 3 billion miles of
DNA inside you!
What is a Gene?
A gene is one set of
instructions for an
inherited trait.
• Each cell in the human
body contains about
25,000 to 35,000 genes
GENES
Genes are found on chromosomes-
there can be hundreds or even
thousands of genes on a
single
chromosome.
Genes determine physical traits, such
as the color of your eyes, the color
of your hair, and your height.
GENES
Genes can be
DOMINANT or RECESSIVE.
• Dominant genes are passed down even if
there is only one copy of that gene in the
pair.
• For a recessive gene to be passed down,
the person must have that gene on both
chromosomes of the pair.
DOMINANT TRAIT
RECESSIVE TRAIT
BROWN EYES
HAZEL EYES
DARK HAIR
BLUE EYES
CURLY HAIR
BLONDE HAIR
FRECKLES
STRAIGHT HAIR
Study Jams- Heredity