MI BIG
Heredity III.3
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(Inspiration)
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All students will investigate and explain how characteristics of living
things are passed on through generations.
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All students will explain why organisms within a species are different
from one another.
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All students will explain how new traits can be established by changing
or manipulating genes.
Overview
The DNA molecule.... so small, so intricate, so important and now so
common in our vocabulary. "Why is your hair curly?" "Why
does your tongue curl?" "What color of coat will the new litter
of puppies probably have?" "How much corn per acre will be
produced with seed from a particular genetic cross?" All of these are
questions we commonly ask each other now that our language includes such
terms as DNA and DNA testing. Even more fascinating may be the individual
differences within a species and where they originate. Human diseases that
occur within families can be traced and determined to help in making
decisions that we as a population are just beginning to experience.
Essential Background Narratives
Investigate and explain how characteristics of living things are passed on
through generations.
Explain why organisms within a species are different from one another.
Explain how new traits can be established by changing or manipulating
genes.
Like produces like. To enable a child to understand why grandparents claim
that they look just like their parents at their age requires many learning
experiences. Elementary students should be able to provide evidence that
visible traits are passed on from parents to children by comparisons of
color, structure, and direct measurements. They should be able to match
offspring to corresponding parents.
By middle school, students should know how characteristics of living
things are passed from generation to generation. Common traits controlled
by a single gene pair should be taught in the middle school years as well
as the reproductive cells which facilitate this happening. They should be
aware that when the sperm fertilizes the egg, the sperm passes the genetic
material (genes) of the father to the egg. The genes of the father's sperm
and mother's egg then contribute to the formation of an entirely new
individual having characteristics from both parents.
Students at the high school level should understand that genes occur and
act in pairs. If a dominant gene is present, it is fully expressed. A
recessive gene will not be expressed in the presence of a dominant gene. A
cross or combination of other gene pairs can show what future generations
may inherit, or predict those chances of traits being exhibited such as
sickle cell anemia and other genetic disorders.
The characteristics of offspring are not only determined by the heredity
from the parents. There are acquired traits like spoken language, size of
a superfertilized plant vs. a tundra plant, or length of hair, which
contributes to the individuality of the offspring. High school students
should also be aware of how genetic material is passed from parent to
offspring during sexual and asexual reproduction. Cell division of
non-sexual cells or somatic cells is an essential process to the growth of
an organism as well as a species. Cell division is comprised of two
processes. Division of the nucleus of the non-sexual cell is called
mitosis which is immediately followed by the division of the cytoplasm and
cellular content producing two daughter cells. Division and replication of
the nuclei of the sex cells is called meiosis and is immediately followed
by two consecutive divisions of cytoplasm and cellular content producing
four daughter cells.
How new traits may arise in individuals through changes in genetic
material should also be taught during the high school years. Students
might misinterpret genetic changes as only detrimental. Gene or chromosome
mutations or recombination of genes can increase the variations that are
seen among individuals in a population. In order to understand this, the
entire DNA molecule and its intricacies of replication need to be
understood. An extension of this could include products of genetic
engineering, natural and human produced mutations, and variations from
multiple sets of genes.
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