Transcript How Does DNA Control Traits? - 6thgrade

How Does DNA Control Traits?
Lesson 3 pg. A52
Ms. Lourdes Martinez 6th Grade
Unique DNA
• A giraffe belongs to a species that is different from the
species that the zebras belong to. Each animal has all
the physical characteristics, or traits, of the species to
which it belongs.
• How do the traits of these giraffes and zebras differ?
• Inside the nucleus of each giraffe cell is a set of instructions for
building the giraffe’s body.
• You’ve already learned that chromosomes are the parts of a
cell’s nucleus that carry information that controls all the cell’s
activities.
• Chromosomes
contain
a
substance
called
DNA
(deoxyribonucleic acid). The DNA determines the kind of
organism that the cell belongs to, in this case a giraffe.
Down
Syndrome
• Most people have 23
pairs
of
chromosomes, for a
total of 46.
• But a baby with Down
syndrome has an
extra
chromosome
(47 instead of 46) or
one chromosome has
an extra part.
• This extra genetic
material
causes
problems with the
way their bodies
develop.
• http://www.ds-int.org/what-down-syndrome
• The DNA of a chromosome is
divided into sections called
genes. Each gene controls
how a certain trait will
develop.
For example – a gene might
control the color of a giraffe’s
hair. The body of the giraffe
will look a certain way
because of a particular gene.
• No two living things that are
produced
by
sexual
reproduction
(except
identical twins) have exactly
the same genes.
Structure of DNA
• The shape of the DNA
molecule looks like a long
twisted ladder. The ladder
has millions of rungs made of
four
kinds
of
smaller
molecules called bases.
• The
four
bases
are
represented by the letters
A,T,G, and C.
• Bases have shapes that
allow them to fit together
only in certain combinations.
Using DNA Information
• Humans contains at least 100,000
organized into 46 chromosomes.
genes
Lesson 3 Review pg.A59
1.- Why is every organism unique?
2.-What are chromosomes?
3.- What does DNA stand for?
4.- Where can we find DNA?
5.- People who are born with Down Syndrome have
how
many
chromosomes?
In
what
pair
of
chromosomes does this problem occur?
6.- The DNA of a chromosome is divided into sections.
What are these sections called?
How Do Organisms Inherit
Traits?
Lesson 4 pg.A62
Variation
• Family Picture
• The process by which traits are passed from parent to
offspring- from generation to generation- is called heredity.
• Remember that DNA in the egg cell combines with DNA in
the sperm cell during fertilization. Then a single cell – the
zygote – forms.
• Organisms that are produced as a result of sexual
reproduction receive, or inherit, at least two genes
for every trait. One gene is inherited from the
mother . The other gene is inherited from the father.
• Not every child in a family receives the same set of
genes from the mother and father. Each egg cell of
the mother contains a different combination of
genes. Each sperm cell of the father also contains a
different combination of genes.
*The appearance of each child in the family results
from the particular combinations he or she received
during fertilization.
Dominant and Recessive Genes