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Ch 12 DNA and RNA

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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.

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Presentation Transcript
slide1

Ch 12

DNA and RNA

slide2

What is DNA?

  • 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.
slide3

Nucleotides

  • Nucleotides- subunits of DNA made of:

1. Phosphate (PO4)

2. Sugar (deoxyribose).

3. Nitrogen base.

slide4

Nitrogen Bases

  • 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.
chargaff s rule
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
Structure of DNA
  • Discovered by Watson and Crick
  • Double helix- 2 spiral strands of nucleotides bonded together
structure of dna1
Structure of DNA
  • Siderail backbone is the sugar and phosphates of nucleotides
  • Rungs are the nitrogen bases of nucleotides
    • A----T
    • C----G
  • Hydrogen bonds between bases hold two strands together
what is dna replication
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
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
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
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
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

slide15

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

slide16

2 Types of Cells

  • Somatic cells –all body cells except sex cells
    • Diploidchromosomes 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 total)

body cells

46 chromosomes

sperm

23 chromosomes

egg

23 chromosomes

slide17

Human 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
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.
  • Protein - polymer of amino acids

aa—aa—aa—aa—aa—aa—aa—aa = protein

  • Why are proteins important?
  • Proteins make up about 15% of the mass of the average person. Muscle, cartilage, ligaments, skin and hair - these are all mainly protein materials.
  • Smaller protein molecules play a vital role in keeping our body working properly. Haemoglobin, hormones (such as insulin), antibodies , and enzymes are all examples of proteins.
what is the purpose of dna1
What is the Purpose of DNA?
  • DNA stores the genetic information that codes for proteins.
  • ALL CELL FACTORIES MAKE PROTEINS!
rna ribonucleic acid
RNA (Ribonucleic acid)

_____DNA____ vs._____RNA___

Transmits the genetic code

to the rest of the cell.

Single stranded

Sugar of RNA nucleotides is

ribose

A, C, G, U (uracil) NO T!

Different forms: mRNA, rRNA, tRNA

Found all over cell

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

part 1of protein synthesis transcription
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)

part 2 of protein synthesis translation
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 translation1
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

slide25

Part #1

Transcription

cytoplasm

Part #2

Translation

whole process
Whole Process

Part #1

Transcription

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!!!

cytoplasm

Part #2

Translation

whole process1
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
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.
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