Benchmark 5B
The Living Environment: Heredity
Grades 6-8, page 108
In some kinds of organisms, all the genes come from a single parent,
whereas in organisms that have sexes, typically half of the genes come
from each parent.
NSES Content Standard C
Life Science: Reproduction and heredity
Grades 5-8, page 157
Reproduction is a characteristic of all living systems; because no
individual organism lives forever, reproduction is essential to the continuation
of every species. Some organisms reproduce asexually. Other organisms reproduce
sexually.
NSES Content Standard C
Life Science: Reproduction and heredity
Grades 5-8, page 157
In many species, including humans, females produce eggs and males produce
sperm. Plants also reproduce sexually--the egg and sperm are produced in
the flowers of flowering plants. An egg and sperm unite to begin the development
of a new individual. That new individual receives genetic information from
its mother (via the egg) and its father (via the sperm). Sexually produced
offspring never are identical to either of their parents.
NSES Content Standard C
Life Science: The molecular basis of heredity
Grades 9-12, page 185
Most of the cells in a human contain two copies of each of 22 different
chromosomes. In addition, there is a pair of chromosomes that determines
sex: a female contains two X chromosomes and a male contains one X and
one Y chromosome. Transmission of genetic information to offspring occurs
through egg and sperm cells that contain only one representative from each
chromosome pair. An egg and a sperm unite to form a new individual. The
fact that the human body is formed from cells that contain two copies of
each chromosome--and therefore two copies of each gene--explains many features
of human heredity, such as how variations that are hidden in one generation
can be expressed in the next.
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