HOW DNA WORKS 42

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HOW DNA WORKS (4-2)
By Brianna Simpson and Abbey Halula
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INTRODUCTION
DNA is found in the cells of all
organisms. Almost every cell in your body
contains about 2 meters of DNA.
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UNRAVELING DNA
DNA is wound around proteins, coiled into
strands, and then bundled up even more. If the
DNA doesnt have a nucleus, it has a loose
loop. If the DNA has a nucleus, it is bundled
into chromosomes.
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MORE UNRAVELING
In DNA, the order of the bases on one side of the
molecule is a code that carries information. A
gene consists of a string of nucleotides that
give the cell information about how to make a
specific trait. There is an enormous amount of
DNA, so there can be a large variety of genes.
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GENES AND PROTEINS
The DNA code is read like a book. Groups of three
bases are codes for amino acids. A long string of
amino acids forms a protein. Thus, each gene is
usually a set of instructions for making a
protein.
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Proteins and Traits
Proteins are found throughout cells and cause
most of the differences that you can see among
organisms. Proteins determine how tall you grow,
what colors you can see, and whether your hair is
curly or straight. Proteins exist in an almost
limitless variety.
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HELP FROM RNA
Ribonucleic Acid (RNA) serves as a temporary copy
of a DNA sequence. A ribosome is a cell
organelle composed of RNA and protein (location
of protein synthesis).
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The Making of a PROTEIN

• Messenger RNA (a mirror-like copy of the DNA)
  moves out of the nucleus and into the cytoplasm.
• The messenger RNA is fed through a ribosome three
  bases at a time.
• Transfer RNA translates the message, picks up
  amino acids from the cytoplasm, and matches them
  up with the messenger RNA.
• The amino acids become a growing chain a new
  PROTEIN.

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MUTATIONS
Mutations changes in the number, type, or order
of bases on a piece of DNA. Deletion is when you
subtract a base. Insertion is when you add an
extra base. Substitution is when the wrong base
is used.
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DO MUTATIONS MATTER?
Three possible consequences an improved trait,
no change, or a harmful trait. Cells make some
proteins that can detect errors in DNA. When an
error is found, it is usually fixed. Occasionally,
the repairs are not accurate then, the mistakes
become part of the genetic message If the
mutation occurs in a SEX CELL, then it can be
passed from one generation to the next.
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HOW DO MUTATIONS HAPPEN?
Mutations occur because of random errors when DNA
is copied. Damage to DNA can be caused by
abnormal things that happen to cells (ultraviolet
radiation, asbestos, cigarette smoke, etc.). Any
physical or chemical agent that can cause a
mutation in DNA is called a mutagen.
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Sickle Cell Anemia
A mutation, such as substitution, can be harmful
because it may cause a gene to produce the wrong
protein. This simple change can cause the disease
Sickle Cell Anemia. Sickle cells cannot carry
oxygen well. They can get stuck in blood vessels
and cause not only painful, but dangerous clots.
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Helpful Mutations

• Not all mutations are harmful. Some mutations
  are helpful and improve an organisms chances for
  survival OR they cause desirable traits in
  organisms that are useful to humans.
• Crop plants increase size and number.
• Katahdin potato resistant to diseases that
  attack other varieties.
• Seedless navel oranges sweeter and juicier.

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GENETIC ENGINEERING
Scientists can use genetic engineering to produce
new products such as drugs, foods, and
fabrics. Scientists worry about the dangers of
creating genetically engineered organisms.
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GENETIC IDENTIFICATION
DNA can be used like a fingerprint
(identification). Identical twins have truly
identical DNA. Cloning is possible, but
politicians and scientist are still debating.
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THE END
THE END