Chapter 11
DNA, RNA and Proteins
• Deoxyribonucleic Acid- type of nucleic acid
• DNA is the code for manufacturing all the proteins for an organism.
• DNA is made of nucleotides
What is DNA?What is DNA?
• Nucleotides have three parts: a simple sugar, a phosphate group, and a nitrogenous base.
Phosphate group
Sugar (deoxyribose)
Nitrogenous base
The structure of nucleotidesThe structure of nucleotides
NitrogenNitrogen BasesBases: adenine (A), guanine (G) cytosine (C), and thymine (T).
Adenine (A) Guanine (G) Thymine (T)Cytosine (C)
•Pyrimidines•Purines
SugarSugar - deoxyribose .
Nucleotide Structure
Base PairingBase Pairing
Adenine – Thymine
Cytosine - Guanine
A - T
C-G
A-T
C-G
A - T
C-G
A - T
A-T
•C-G
• In DNA, the amount of adenine is always equal to the amount of thymine, and the amount of guanine is always equal to the amount of cytosine.
The structure of nucleotidesThe structure of nucleotides
• Nucleotides join together to form long chains
• Phosphate groups and deoxyribose molecules- form the backbone of the chain
The structure of DNAThe structure of DNA
It is a double helix and is twisted
Chromosome The sequence of nucleotides forms the unique genetic information of an organism.
REPLICATION
ReplicationReplication
Before mitosis or meiosis, the chromosomes are copied – this is called DNA replication.
Happens during Interphase
The new DNA is identical to original DNA
Replication of DNA
Replication of DNA
DNA
Replication
Replication
Copying DNACopying DNA
Original DNA
Original DNA
Strand
Original DNA
Strand
Free Nucleotides New DNA
moleculeNew DNA
Strand
New DNA molecule
Replication of DNA
Replication of DNA
Click this image to view movie
type of nucleic acid
single stranded
RNARibonucleic acid
RNARibonucleic acid
sugar is ribose Ribose
RNARNA
Nitrogen bases:
adenine – uracil
cytosine - guanine
Uracil
Hydrogen bonds Adenine
RNARNA
•NO thymine
Comparing DNA and RNAComparing DNA and RNA
DNA
1. double stranded
2. sugar – deoxyribose
3. nitrogen bases
- adenine-thymine
- cytosine-guanine
RNA
1. Single stranded
2. Sugar – ribose
3. Nitrogen bases:
- adenine- uracil
- cytosine- guanine
Proteins are made of amino acids.
The sequence of nucleotides in each gene contains the code for making the string of amino acids that make up a protein.
Genes and ProteinsGenes and Proteins
TranscriptionTranscription
1. DNA - instructions for making proteins (proteins are made of amino acids)
2. RNA transcribes the instructions from the DNA- mRNA
• Messenger RNA (mRNA), brings instructions from DNA in the nucleus to the ribosomes. (in the cytoplasm)
mRNA
Difference in Replication and TranscriptionDifference in Replication and Transcription
• Replication – forms a double stranded DNA molecule from the DNA in the nucleus and it is identical to the original DNA
• Transcription – forms a single stranded RNA molecule called mRNA from the DNA that is in the nucleus
DNA separates – mRNA is assembled A A TC C GG G CG G CC C GT U AT U AC C G
DNA DNA
TranscriptionTranscription
Translation: From mRNA to ProteinTranslation: From mRNA to Protein
1. mRNA is made in the nucleus and travels to the ribosomes in the cytoplasm.
- ribosomes are made of rRNA (ribosomal RNA)
2. ribosome attaches to the mRNA
tRNA –( transfer RNA) – brings the correct
amino acid to the ribosome to make the protein
• Transfer RNA (tRNA) is the supplier. Transfer RNA delivers amino acids to the ribosome to be assembled into a protein.
RNARNA
Click image to view movie
TranslationTranslation
• Strand of mRNA
AUG UAA CGA CGA GAU GUG UGA
• Codon – set of three nitrogenous bases that represent an amino acid (the order of the nitrogen bases is the recipe for the protein)
AUG UAC CGA CGA GAU GUG UGA
Methionine, Tyrosine, Arginine, Arginine, Aspartic Acid, Valine, Stop
Each codon represents an amino acid
mRNA strand
Try one!!!! Write the amino acids that correspond to the codon!!!!
AUG UUU ACA AAA GGG GAG GUC UAA
• methionene, phenylalanine, threonine, lysine, glycine, glutamic acid,valine,stop
Now try something different- here is the mRNA – write what the DNA code was for this mRNA.
AUG UUU ACA AAA GGG GAG GUC UAA
TAC AAA TGT TTT CCC CTC CAG ATT
Review of Translation
1. mRNA leaves the nucleus and goes to the ribosome
2. mRNA has the code for making the protein
3. tRNA brings the correct amino acid to the ribosome to make the protein
Mutation
Any change in the DNA sequence
Mutations
Body cell – damage to a gene may impair the function of the cell
- ex: cancer
Reproductive Cell – mutation could become a part of the genetic makeup of the offspring
-ex:genetic disorder, death
Types of mutations
Point mutation – a change in a single base pair in DNA – wrong amino acid
- ex: CCC – codon for proline CGC(mutation) – codon for arginine Insertion – an extra base pair inserted – changes
the codon
Deletion – a base pair is missing – again changes the codon
Results in a frameshift mutation- it shifts the reading of codons so has the wrong amino acids
for the protein
PracticeDNA strand:
TAC AAA TGT TTT CCC CTC CAG ATT
RNA strand:AUG UUU ACA AAA GGG GAG GUC UAA
Amino Acids making up the protein: •methionene, phenylalanine, threonine, lysine, glycine, glutamate,valine,stop
Point mutationDNA strand:
TAC AAA TGT TAT CCC CTC CAG ATT
RNA strand:
AUG UUU ACA AUA GGG GAG GUC UAA
Amino Acids making up the protein: • methionene, phenylalanine, threonine,
isoleucine, glycine, glutamate,valine,stop
Frameshift Mutation
DNA strand: (deletion)
TAC AAA TGT TT CCC CTC CAG ATT
RNA strand:
AUG UUU ACA AA GGG GAG GUC UAA
AUG UUU ACA AAG GGG AGG UCU AAG
Amino Acids making up the protein: • methionene, phenylalanine, threonine,
lysine,glycine,arginine, serine, lysine
Chromosomal mutations
• Deletion-part of the chromosome is left out
• Insertion- part of chromatid breaks off and attaches to its sister chromatid (duplication of genes on one chromosome)
• Inversion – when a chromsome breaks off and reattaches backwards
• Translocation- part of one chromosome breaks off and is added to a different chromosome
Causes of mutations• Mutagen- any thing that causes a change
in the DNA
- radiation, chemical , UV light, nuclear
radiation, asbestos,