ch 12 dna and rna
DESCRIPTION
Ch 12 DNA and RNA. What is DNA?. D NA ( d eoxyribo n ucleic a cid)- a nucleic acid which stores genetic traits in the proteins it codes for. All living things contain DNA. D NA is a n ucleic a cid. Nucleic acids are made of nucleotide subunits hooked together. Nucleotides. - PowerPoint PPT PresentationTRANSCRIPT
DNA (deoxyribonucleic acid)- a nucleic acid which stores genetic traits in the proteins it codes for.
All living things contain DNA. DNA is a nucleic acid. Nucleic acids are made of
nucleotide subunits hooked together.
Nucleotides- subunits of DNA made of:
1. Phosphate (PO4)
2. Sugar (deoxyribose).
3. Nitrogen base.
Nucleotides
Four different nitrogen bases makes four different nucleotides:– Guanine– Cytosine– Adenine– Thymine
These four nucleotides make up the DNA of almost every single living thing.
Nitrogen Bases
Nucleotides
Chargaff’s Rule He measured amounts of each base
in various organisms and found: % of adenine (A) = % thymine (T)
% of cytosine (C) = % guanine (G) Chargaff’s rule told us that A bonds
to T and C bonds to G If 20% of strand is A, what %T?
%C?
Structure of DNA Discovered by Watson and Crick Double helix- 2 spiral strands of nucleotides
bonded together
Structure of DNA
Siderail backbone is the sugar and phosphates of nucleotidesRungs are the nitrogen bases of nucleotides
–A----T –C----G
Hydrogen bonds between bases hold two strands together
What is DNA Replication? Replicate = make “exact” copies. DNA replication- copying of DNA so that a cell
made divide All DNA must be
replicated before a cell can divide. Why?
Enzymes and Replication
Helicase- enzyme that unwinds DNA
DNA polymerase-enzyme that moves along each strand and brings in bases for new strand copy
DNA Replication Can be a mistake in replication Mutations-change in DNA Mutagens- substances that cause mutations
– X-rays – Toxins– Drugs– UV light, etc.
Mutations
3 types of mutations that can occur during DNA replication: – Insertions -extra
nucleotides– Deletions –missing
nucleotides– Substitutions –placement
of wrong nucleotides Can be helpful or harmful
mutations.
Insertion
Deletion
Substitution
Most Destructive Mutation?
The bases, A, C, G, and T can be equated to letters of a “DNA sentence”
THE DOG WAS HOT IN THE SUN Substitution:
THE DOG WAS NOT IN THE SUN Insertion?
THE DOG NWA SHO TIN THE SUN Deletion? THE DOG ASH OTI NTH ESU N Why should I care?
How Much DNA Is In OUR Cells?
Chromosome-strands of DNA coiled tightly Human cell has 46 (23 pairs)
23 from Mom 23 from Dad
Other organisms
have different
numbers of
chromosomes
2 Types of Cells
Somatic cells –all body cells except sex cells Diploidchromosomes are in pairs 46=23 pairs for humans 1 set (23) from mom, 1 set (23) from dad
Gametes - sex cells Egg & sperm Haploid no pairs (only 23 single chromosomes)
If all body cells contain the same # of chromosomes, why are all cells so different?
Different cells make different proteins due to different “active” segments of DNA.– Heart cells make proteins needed for the heart
to work properly– Brain cells make proteins needed for the brain
to work properly
What is the Purpose of DNA?
DNA stores the genetic information that codes for proteins.
ALL CELL FACTORIES MAKE PROTEINS!
What is the Purpose of DNA?Gene- a segment of DNA that codes for a protein.DNA has 1000’s of genes to make many different types of proteins.Why are proteins important?
Protein - polymer of amino acids
aa—aa—aa—aa—aa—aa—aa—aa = protein
What is the Purpose of DNA?
RNA (Ribonucleic acid)
Stores the genetic code in the nucleus
Double stranded
Sugar of DNA nucleotides = deoxyribose
A, C, G, T
“DNA is DNA”
Found in nucleus only
Transmits the genetic code to the rest of the cellSingle strandedSugar of RNA nucleotides is riboseA, C, G, U (uracil) NO T!Different forms: mRNA, rRNA, tRNAFound all over cell
_____DNA____ vs._____RNA___
DNA vs. RNA
Part 1of Protein Synthesis: Transcription
Transcription- copying of DNA to mRNA that occurs in the nucleus.
DNA complementary to mRNA ATA-CGG-AAT (DNA)
transcription in nucleus
UAU-GCC-UUA (RNA)
Transcription
Translation
cytoplasm
Part 2 of Protein Synthesis: Translation:
Translation- converting mRNA to protein which occurs at ribosomes in the cytoplasm
mRNA codons
translation by ribosomes
a.a.---a.a---a.a (protein)
cytoplasm
Part 2 of Protein Synthesis: Translation:
Codon-three bases of mRNA that code for an amino acid UAU-GCC-UUA (3 mRNA codons)
translation by ribosomes
a.a.---a.a---a.a. (protein) mRNA needs the help of tRNA to bring in the amino acids to be hooked together
cytoplasm
Whole Process ATA-CGG-AAT (DNA)
transcription in nucleus
UAU-GCC-UUA (3 mRNA codons)
translation in cytoplasm at ribosomes
a.a.-a.a-a.a. (protein)
How do we know what amino acid results?
The Codon Wheel!!!
Part #1Transcription
Part #2Translation
cytoplasm
The Codon Wheel***How do we use the wheel? There are 2 clues.
The Codon Wheel
Whole Process DNA: ATA-CGG-AAT
transcription in nucleus
mRNA: UAU-GCC-UUA(3 codons)
translation in cytoplasm
protein: a.a.-a.a-a.a.
tyrosine-alanine-leucine
Protein Synthesis Animation!
How do we know what amino acid results?
The Codon Wheel!!!
Amino Acids Where do our cells get
these amino acids to build the proteins?
From FOOD! We eat proteins, then these
proteins are broken down (metabolized) into amino acids in our stomach.
We reuse these amino acids to build other proteins.