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Curriculum Organizing Questions
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- What role(s) does DNA play in the transmission of
information?
- What role(s) does RNA plan in the transmission of
information?
- What are genes and do all cells have them?
- How can cells that arise from the same single cell be
so different?
- How do cells transmit information?
- How do genes encode information?
- How can we describe the templating mechanism for
DNA?
- What are chromosomes?
- How are your chromosomes like my chromosomes?
- What roles do sperm and egg play in human
reproduction?
- How can variations hidden in one generation be
expressed in the next?
- What are mutations and are they always bad?
- What does DNA code for?
- How is DNA replicated?
- What role do cell membranes play in transmission of
information?
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Elaboration
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The details of transcription and translation can be
used to illustrate these ideas, but students need not
memorize all of the details of the process.
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Specific Ideas
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- The information passed from parents to offspring is
coded in DNA molecules. Benchmarks 5B3
- Genes are segments of DNA molecules. Benchmarks
5B4
- Different parts of the instructions are used in
different types of cells, influenced by the cell's
environment and past history. SFAA p.63-4
- Communication between cells is required to coordinate
their diverse activities. Some cells secrete substances
that spread only to nearby cells. Others secrete
hormones, molecules that are carried in the bloodstream
to widely distributed cells that have special receptor
sites to which they attach. Along nerve cells, electrical
impulses carry information much more rapidly than is
possible by diffusion or blood flow. Benchmarks 6C3
- In all organisms, the instructions for specifying the
characteristics of the organism are carried in DNA, a
large polymer formed from subunits of four kinds (A, G,
C, and T). NSES C2a
- The chemical and structural properties of DNA explain
how the genetic information that underlies heredity is
both encoded in genes (as a string of molecular
"letters") and replicated (by a templating mechanism).
NSES C2a
- Each DNA molecule in a cell forms a single
chromosome. NSES C2a
- 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. NSES C2b
- 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. NSES C2b
- The fact that the human body is formed from cells
that contain two copies of each chromosome-and therefore
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. NSES C2b
- Changes in DNA (mutations) occur spontaneously at low
rates. Some of these changes make not difference to the
organism, whereas others can change cells and organisms.
Only mutations in germ cells can create variation that
changes an organism's offspring. NSES C2c
- The genetic information encoded in DNA molecules
provides instructions for assembling protein molecules.
Benchmarks 5C4, SFAA p. 64
- Some protein molecules assist in replicating genetic
information. Science Matters p. 232
- Every cell is covered by a membrane that controls
what can enter and leave a cell. Benchmarks 5C1
- In some kinds of organisms, all of the genes come
from one parent. Benchmarks 5B1 (gr 6-8)
- RNA molecules are involved in making proteins from
the information encoded in the DNA. Science Matters p.
232
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Developmental & Instructional
Implications
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Students believe that a mutation modifies an individual's
own form during its life, rather than only its germ cells
and offspring. Benchmarks p. 343
Many students view genetic variation as a response to
environment, rather than due to inheritance. Driver p.
51
Many pupils do not believe that plants reproduce
sexually. Driver p. 50
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Examples
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