Transcript Chapter 2 lesson 2

Chapter 2
Lesson 2
Traits and Heredity
What is heredity?
• Heredity : the passing down of traits from
parents to offspring.
• Inherited trait: a trait that an offspring
receives from its parents. (dimples, hair and
eye color, facial features, even a laugh.
• Instinct: a way of acting or behaving that an
animal is born with and does not have to
learn. (a spider spinning a web)
How are traits inherited?
• Dominant Trait: A strong trait passed along by
a parent to an offspring. (Both parents have
brown eyes, the child is likely to have brown
eyes.)
• Recessive Trait: If both parents of a child carry
the dominant and recessive genes, there is a
25% chance that the child will develop the
recessive trait.
How are traits inherited?
• Genes:
Chromosomes,
contain the DNA
codes for all the
traits an organism
inherits.
How do we trace inherited traits?
• Gregor Mendel: monk who studied and
discovered the basic principles of heredity.
Mendel discovered that for every trait there is
a dominant form and a recessive form.
How do we trace inherited traits?
• A pedigree is a chart
used to trace the
history of traits in a
family.
How do we trace inherited traits?
• Carrier: the
individual who has
inherited the gene
for a trait, but does
not physically show
the trait.
Decoding the Human Body
Time for Kids Article
• Have you ever wondered how a chicken egg
manages to grow into a chicken and not a
frog? Or how a frog egg produces a frog and
not a python? The answers lie in their genes,
tiny sets of chemical instructions in every cell
of every creature that contain its recipe. The
recipe for a human being is contained in the
80,000 genes we inherit from our parents.
These genes have the instructions that not only
make us human but also determine things like
skin color and the shape of our nose.
Decoding the Human Body
• Last week Craig Venter, the lead scientist at
Celera Corporation in Maryland, announced
that his team had cracked the chemical code
for every human gene.
• This breakthrough is likely to lead to great
medical advances. Knowing detailed
information about human genes could help
millions of people who suffer from illnesses
caused by mistakes in their gene code. They
could someday undergo genetic treatments to
correct the problems. Doctors may also be able
to detect and prevent illnesses like cancer and
heart disease, which are linked to certain
genes.
Decoding the Human Body
• Scientists have years to go before they can
pinpoint the function of every gene. "We're
assembling one of the biggest jigsaw puzzles
ever imaginable," said Venter.
• The Code of Life
Genes are made of a special chemical called
DNA. It is shaped like a very tiny, twisted
ladder. The rungs of the ladder are made of
four chemicals. These chemicals can appear in
an almost endless variety of patterns. Each
pattern forms the instruction, or code, for a
specific component of the human body.
• What to do: Tracking Traits!
• 1. Begin by drawing a family tree with your child. Start with
your child's great-grandparents, or even great-greatgrandparents, if possible. Fill in as much of the tree as you
can.
2. Decide on which traits to track. Hair color and eye color
are obvious choices, but you could also try to trace abilities
such as singing or sports, or even diseases like diabetes.
What kinds of traits are not inherited?
3. On the tree, mark which family members had the traits
you selected.
4. Help your child record the frequency of the trait on a
graph. Try different kinds of graphing techniques, such as
bar graphs or pie charts.