BIOL 1001 Chapter : Chapter 12
Chapter 12 11/9/2015 6:55:00 AM
12.1 How Is the Information in DNA Used in a Cell?
• A. Most Genes Contain the Information for the Synthesis of a Single
Protein
o 1. Genes provide information to make proteins
o 2. Proteins are the cell’s “molecular workers”
▪ control cell shape, functions, reproduction, and
synthesis of biomolecules
there must be a flow of information from DNA to
protein
• B. DNA Provides Instructions for Protein Synthesis via RNA
Intermediaries
o 1. DNA in eukaryotes is kept in nucleus
▪ protein synthesis occurs in ribosomes of cytoplasm
o 2. Ribonucleic acid (RNA) carries the information in DNA
necessary for making proteins
▪ a. There are structural differences between DNA and
RNA
i. RNA is single stranded
ii. RNA has the sugar ribose instead of
deoxyribose
iii. RNA has the base uracil (U) instead of thymine
(T)
o 2. DNA codes for the synthesis of the three kinds of RNA
▪ a. mRNA
single-stranded “intermediate copy” of DNA
▪ b. tRNA
have a clover shape
▪ c. rRNA
each ribosome consists of two subunits-one small
and one large
o 3. Messenger RNA carries the code for protein synthesis from
DNA to ribosomes
▪ a. RNA takes genetic information from the nucleus to
the cytoplasm
o 4. Ribosomal RNA and proteins form ribosomes
▪ a. The small subunit of the ribosome has binding sites
for mRNA
▪ b. The large subunit of the ribosome has binding sites
for tRNA
o 5. Transfer RNA carries amino acids to the ribosomes
▪ a. Every cell synthesizes at least one tRNA for each
amino acid
▪ b. Complementary base pairs between the tRNA
anticodon and the mRNA codon ensure that the correct
amino acid is used to synthesize a protein
• C. Overview: Genetic Information Is Transcribed into RNA and Then
Translated into Protein
o 1. In transcription, the information contained in the DNA of a
specific gene is copied into mRNA, tRNA, or rRNA
▪ a. This process occurs in the nucleus
o 2. During translation, the mRNA base sequence is decoded
into an amino acid sequence
▪ a. tRNA molecules bring amino acids to the ribosome for
assembly into proteins
o 3. Transcription is the process of copying DNA to RNA using
the nucleotide “language”
▪ a. Translation is the process of translating the
nucleotide “language” into the “language” of amino
acids
• D. The Genetic Code Uses Three Bases to Specify an Amino Acid
o 1. The genetic code translates the sequence of bases in
nucleotides into a sequence of amino acids in a protein
o 2. Codons are sequences of three bases that code for specific
amino acids
▪ decoding the codons of mRNA is the job of the tRNA
o 3. Stop and start codons act as the “punctuation” for a mRNA
sequence
▪ a. The start codon (AUG) signifies the start of the
mRNA message
▪ b. The three stop codons (UAG, UAA, and UGA)
signify the end of the mRNA message
o 4. Anticodons in the tRNA are complementary to the codons
in mRNA
▪ a. The anticodons ensure that the correct amino acid is
placed in the proper sequence in the protein
o 5. The genetic code is redundant
▪ a. There is more than one codon for many amino acids
12.2 How Is the Information in a Gene Transcribed into RNA?
• A. Transcription Has Three Steps: Initiation, Elongation, and
Termination
• B. Initiation: Transcription Begins When RNA Polymerase Binds to
the Promoter of a Gene
o 1. RNA polymerase binds at the promoter region (TATAAA
sequence)
o 2. The DNA begins to unwind
o 3. Creates single strand regions of the DNA
• C. Elongation Generates a Growing Strand of RNA
o 1. RNA polymerase synthesizes RNA that is complementary to
template strand of DNA
o 2. As the RNA strand leaves the DNA strands, the helix re-
forms
• D. Termination: Transcription Stops When RNA Polymerase Reaches
the Termination Signal (UAA/UAG/UGA)
Document Summary
12. 1 how is the information in dna used in a cell: a. Most genes contain the information for the synthesis of a single. Genes provide information to make proteins: 2. Proteins are the cell"s molecular workers : control cell shape, functions, reproduction, and synthesis of biomolecules there must be a flow of information from dna to, b. dna provides instructions for protein synthesis via rna protein. Dna in eukaryotes is kept in nucleus: protein synthesis occurs in ribosomes of cytoplasm, 2. Ribonucleic acid (rna) carries the information in dna necessary for making proteins: a. Rna: rna is single stranded, rna has the sugar ribose instead of deoxyribose, rna has the base uracil (u) instead of thymine (t, 2. Dna codes for the synthesis of the three kinds of rna: a. mrna. Single-stranded intermediate copy of dna: b. trna. Have a clover shape: c. rrna. Each ribosome consists of two subunits-one small and one large: 3.