DNA AND GENES

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Chapter 12 Molecular Genetics
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II. DNA
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DNA The Genetic Material
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A. Structure and Function

• 1. DNA is a complex polymer called a nucleic acid

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2. Nucleic acids are made up of subunits called
nucleotides which include

• a. Deoxyribose sugar
• b. Phosphate group
• c. nitrogen base
• (1) adenine (A)
• (2) guanine (G)
• (3) cytosine ( C )
• (4) thymine (T)

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3. Nucleotides combine to form two long chains
producing one LARGE molecule.
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4. The two chains are internally held together
by hydrogen bonds.
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5. Joined chains twist to form a double helix.
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6. DNA determines the type of organism.
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7. Different orders of nucleotides make
individuals different.
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B. DNA Replication

• 1. DNA must replicate ( make a copy of itself)
  in order for a cell to divide.

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2. DNA replication occurs when

• a. enzyme breaks the H-bonds between the N-bases
• b. Strands unzip
• c. Free nucleotides bond to single strands
  bases.
• d. Enzyme bonds new nucleotides to old bases.
• e. strands are complementary to each other

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f. The leading strand is made continuously but
the lagging strand is made in segments called
Okazaki fragments
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3. Result of Replication is the formation of two
DNA molecules that are IDENTICAL.
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III. DNA to RNA to PROTEINS
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A. Main Idea DNA codes for RNA, which is the
guide for making proteins
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1. Genes are responsible for the production of
proteins.
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2. Proteins have different functions

• a. Control chemical reactions
• (1) production of ATP
• (2) digestion
• Builds and repairs cells
• Transport Substances
• Provide Hormones

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3. Proteins are made from the DNA code which has
been transcribed and then translated
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B. DNAs CODE

• 1. The genetic code is the sequence of
  Nitrogen-bases along one of the two strands of
  DNA that codes for the synthesis of proteins.

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2. Proteins are built from amino acids
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3. Each set of 3 Nitrogen bases is a CODON for
an amino acid.
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Transcription
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1. DNAs message for protein synthesis must get
from the nucleus to the ribosomes.

• RNA is responsible for doing this tasks.

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2. RNA and DNA differ in three ways

• (a) RNA is single stranded-DNA is double stranded

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RNAs sugar is ribose-DNAs sugar is deoxyribose.
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( C ) RNA contains the N-base Uracil (U)- DNA
contains thymine (T)
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3. Transcription

• Process of making RNA from DNA.

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4. Types of RNA

• (a) mRNA
• (1) messenger RNA
• (2) Carries messages
  from DNA to the
  cytoplasm.

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(b) rRNA

• (1) ribosomal RNA
• (2) produces enzymes needed to bond amino acids
  together.

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(c) tRNA

• (1) Transfer RNA
• (2) used in translation to bring amino acids to
  the ribosomes.

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5. 20 amino acids make up proteins

• 4 bases of DNAPage 338 table 12.14

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6. The genetic code is universal.

• The codons represent the same amino acids in all
  organisms.

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Translation-From RNA to Protein
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Process of converting information from mRNA into
a protein
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2. Occurs in the ribosomes
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3. Each mRNA codon pairs with an anticodon of
tRNA
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• 4. Translation results in the formation of
  proteins that makeup and help function all
  organisms.

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Mutations-gene expression is regulated by the
cell and mutations can affect this expression
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A. Mutation is a mistake or change in the DNA
sequence.
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Types of gene mutations (page 342)

• 1. Point mutation- change in a single base pair.

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2. Frameshift mutation

• Base pair is added or deleted.

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C. Types of Chromosomal Mutations ( page 346)

• 1. Deletion
• 2. Insertion
• 3. Inversion

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4. Translocation
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5. Nondisjunction
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IV. Biotechnology
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1. Selective Breeding
2. Genetic Engineering
3. Human Genome Project

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