Dna chapter12 13
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Transcript of Dna chapter12 13
DNA Structure & Function
Chapter 12Random Chapter 13
dna– Has the capacity to store genetic information– Can be copied and passed from generation to
generation– Located in the nucleus of cells– “blueprint” of life
Nucleic acids• Information storage molecules• Directions for building proteins• Found in nuclei of eukaryotes• Two forms
– Deoxyribonucleic acid – Ribonucleic acid
• Polymers of nucleotides
DNA Nucleotide• 5 Carbon sugar
– Deoxyribose– ribose
• Phosphate group• Nitrogenous base
– Adenine– Guanine– Cytosine– Thymine (DNA only)– Uracil (RNA only)
RNA Nucleotide• Sugar-phosphate backbone • Ribose sugar• Complementary Nucleotides
– Uracil (u)– Cytosine (c)– Adenine (a)– Guanine (g)
• RNA has uracil in place of thymine• Single strand• Information transfer and translation
DNA structure• Sugar-phosphate backbone
– Deoxyribose sugar– Covalent bonds
• Complementary Nucleotides– Pyrimidine
• Thymine (T)• Cytosine (c)
– Purine• Adenine (a)• Guanine (g)
• Double helix– Hydrogen bonds
Complementary Base Pair Rule
G-C A-T A-U in RNA
DNA Replication • Template mechanism • DNA strand is unwound and double helix
is separated• Single strand replicated via base pair rule
DNA Function– Stores genetic information– Instructions for all life and life processes
• Contains protein building instructions– Uses specific code built into sequence of
nucleotides
Genetic Code• Genes have nucleotide code for building proteins
– Proteins are made of amino acids• The set of rules giving the correspondence between
nucleotides of nucleic acids and amino acids of proteins• Codon aka Triplet Code
– Sets of 3 nucleotides
Genetic Code
• Each codon represents an amino acid
• Code is redundant• Specific Start & stop
codons• Code is universal to life
Terminology• Gene
– Sequence of nucleotides that is the unit of hereditary information
– Ie. A recipe• Genome
– The sum of an individuals genes
Genes are made of Introns & exons
– Exons • Segments of DNA that
code for AA– Introns
• Sections of nucleotides that do not code for AA
• Regulatory function
Why are proteins so important?
remember…..
Protein Types• Structural• Storage• Contractile• Transport• Defense• Signal• Enzymes
• The one gene–one protein hypothesis states that the function of an individual gene is to dictate the production of a specific protein
Junk DNA
Gene Expression • How dna’s instructions are carried out• This is how genes control the structures and activities
of cells• Code in gene is copied and used to build proteins or run
other jobs
In Animal Cell… DNA is Isolated in the Nucleus
Protein Building Structures in cytoplasm
Transcription vs Translation
• Transcription• Transcription occurs in the nucleus
• Translation• Translation occurs in the cytoplasm
Uses DNA and RNA
Transcription• Converts DNA to RNA
– Results in strand of messenger RNA (template)
– Uses Complementary base pair rule
• Region of copying unwinds & then rewinds after mRNA is complete
Messenger RNA (mRNA)• RNA Template of DNA • Single strand of nucleotides• Uses Uracil instead of Thyamine• Moves from inside nucleus to
cytoplasm
mRNA Is Processed• MRNA is spliced (cut &
paste)– Introns removed
DNA
RNAtranscriptwith capand tail
mRNA
Introns removed Tail
Exons spliced together
Coding sequence
Nucleus
Cytoplasm
TranscriptionAddition of cap and tail
Translation– Converts from nucleic
acid (nucleotide) language to the protein language (amino acid)
– Converts mRNA to protein
Transfer RNA (tRNA)• Molecular translators• Carries specific amino
acid• Matches codon in
mRNA using anticodon• Recycled after each use
Ribosomal RNA
tRNAbinding sites
P site A siteLargesubunit
mRNAbindingsite
Smallsubunit
P site A site
P A
– Site of protein synthesis– Made up of ribosomal RNA (rRNA)– Holds mRNA & tRNA
Mutagen
• Physical or chemical agents that induce change in nucleotide sequence of DNA (aka Mutation)
• Physical– Radiation– X-ray, uv light
• Chemical– carcinogens
• Viral
Mutation• Mutation
– A change in the nucleotide sequence of a nucleic acid
• Point mutations– “switch” nucleotide
• Frame shift mutations– Insertion- add extra nucleotides– Deletions- delete nucleotide
Mutation• Good or bad• Beneficial/ adaptive• deleterious
Epigenetics
• Study of heritable changes in gene expression caused by mechanisms other than DNA sequence
• http://video.pbs.org/video/1525107473/
Lyonisation• Mary Lyon 1962• In Females each somatic cell has 2 X chromosomes
– One X chromosome is inactivated– Random inactivation
• Shortened and condensed• Females are genetic mosaics
Lyonisation
• Occurs only in females• X chromosome has fur color
control gene• 2 alleles
– Black & Orange• White results from genetic
condition of unpigmented hair