Chapter 12Chapter 12

Nucleic Acids Nucleic Acids and and

Protein SynthesisProtein Synthesis

DNA: Structure and Shape DNA: Structure and Shape Composition: a nucleotide has these 3 things:: a nucleotide has these 3 things:

– Deoxyribose (a sugar)Deoxyribose (a sugar)– Phosphate GroupPhosphate Group– Nitrogen-containing bases Nitrogen-containing bases

(N-bases)(N-bases)Purines:Purines:1.1. Adenine (A)Adenine (A)2.2. Guanine (G)Guanine (G)

PyrimidinesPyrimidines3. Thymine (T)3. Thymine (T)4. Cytosine (C)4. Cytosine (C)

Shape: Double helixShape: Double helix

Replication: DNA copies itself: DNA copies itself

Steps::– The nucleotide chain separates and unwindsThe nucleotide chain separates and unwinds

Each chain serves as a template for the next stepEach chain serves as a template for the next step

The enzyme helicase helps the processThe enzyme helicase helps the process

– Complementary nucleotides that are free-Complementary nucleotides that are free-floating in the nucleus, assemblefloating in the nucleus, assemble

– Nucleotides join by Hydrogen bondsNucleotides join by Hydrogen bonds

Products: Two new DNA strands (this Products: Two new DNA strands (this occurs before a cell divides).occurs before a cell divides).

RNA: Composition and Shape: Composition and Shape

Composition:Composition:– Ribose (a sugar)Ribose (a sugar)– Phosphate groupPhosphate group

--N-base: --N-base: Adenine(A), Adenine(A),

Uracil(U), Uracil(U),

Cytosine (C), and Cytosine (C), and

Guanine (G)Guanine (G)

Shape: single-strandedShape: single-stranded

RNA: TypesRNA: TypesmRNA – messenger RNA carries info from mRNA – messenger RNA carries info from DNA in the nucleus to the cytosol.DNA in the nucleus to the cytosol.

tRNA- transfer RNA takes info from the tRNA- transfer RNA takes info from the mRNA and binds to amino acids.mRNA and binds to amino acids.

rRNA- ribosomal RNA exists where proteins rRNA- ribosomal RNA exists where proteins are made.are made.

Transcription: DNA makes RNA: DNA makes RNA

Steps:Steps:– DNA unwindsDNA unwinds– Complementary RNA nucleotides assembleComplementary RNA nucleotides assemble– Nucleotides of RNA join and separate from Nucleotides of RNA join and separate from

DNA moleculeDNA molecule

Results: Results: – DNA passes info (transcribes) onto RNA.DNA passes info (transcribes) onto RNA.– RNA molecules exit the nucleus and go to RNA molecules exit the nucleus and go to

ribosomes for protein synthesis.ribosomes for protein synthesis.

Translation – Protein SynthesisTranslation – Protein Synthesis

Composition of Proteins: chains of amino acidsComposition of Proteins: chains of amino acids– Each of the 20 amino acids are coded for by a Each of the 20 amino acids are coded for by a

specific sequence of 3 mRNA nucleotides (p 303)specific sequence of 3 mRNA nucleotides (p 303)

Steps of Process: Steps of Process: codes from mRNA are from mRNA are translated into making proteins (p 304)translated into making proteins (p 304)– mRNA leaves nucleus and goes to ribosomesmRNA leaves nucleus and goes to ribosomes– Amino acids are carried to the ribosomes by tRNAAmino acids are carried to the ribosomes by tRNA– tRNA carries anticodons complementary to the tRNA carries anticodons complementary to the

codons of mRNA and in joining, the amino acids are codons of mRNA and in joining, the amino acids are connected in a certain sequence to produce proteins.connected in a certain sequence to produce proteins.

translation:translation:

Summary – from replication to Summary – from replication to translationtranslation

More . . .More . . .

DNA composition Quiz Quiz

DNA replication quiz

Transcription Quiz

RNA Types Quizypes Quiz

Translation Quiz

12.4 Mutations: 12.4 Mutations: changes in genetic materialchanges in genetic material

Gene Mutations: Gene Mutations: changes in one or a few changes in one or a few nucleotides affecting one genenucleotides affecting one gene– Point mutationsPoint mutations– Frameshift mutationsFrameshift mutations

Chromosomal mutations: Chromosomal mutations: involves changes in the involves changes in the number and structure of chromosomesnumber and structure of chromosomes

Significance:Significance:– Neutral effectsNeutral effects– DisordersDisorders– Genetic variability among speciesGenetic variability among species– Polyploidy in plantsPolyploidy in plants

12.5 Gene 12.5 Gene RegulationRegulation

Terms:Terms:– OperonOperon– DifferentiationDifferentiation– Hox genesHox genes