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DNA & Genes Chapter 12 DNA, RNA, & Protein Synthesis

DNA & Genes Chapter 12

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DNA & Genes Chapter 12. DNA, RNA, & Protein Synthesis. DNA Molecule of Heredity A. Structure. DNA (polymer) is a long molecule made up of Nucleotides (monomers) A Nucleotide consists of: Deoxyribose (a 5-carbon sugar) a phosphate group One of 4 Nitrogenous bases (contain nitrogen) - PowerPoint PPT Presentation

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Page 1: DNA & Genes Chapter 12

DNA & GenesChapter 12

DNA, RNA, & Protein Synthesis

Page 2: DNA & Genes Chapter 12

I. DNA Molecule of HeredityA. Structure

• DNA (polymer) is a long molecule made up of Nucleotides (monomers)

• A Nucleotide consists of: – Deoxyribose (a 5-carbon sugar) – a phosphate group– One of 4 Nitrogenous bases (contain nitrogen)

• Adenine (A)

• Guanine (G)

• Cytosine (C)

• Thymine (T)

PURINES

PYRIMIDINES

•The nitrogenous bases of DNA (purines – double ring / pyrimidines single ring)

Page 3: DNA & Genes Chapter 12

DNA

• Deoxyribonucleic acid• Deoxyribose is sugar• Nitrogenous bases:

Adenine binds with Thymine

Cytosine binds with Guanine

One nucleotide of DNA

Page 4: DNA & Genes Chapter 12

Structure of DNA (cont.)

• DNA is like a twisted ladder:– Rungs: complementary base pairs (A=T, G=C)– Uprights: deoxyribose and phosphate groups

• Your Turn: Match this DNA base sequence with its correct complementary DNA bases:

• T-C-G-A-A-C-T• A-G-C-T-T-G-A

Page 5: DNA & Genes Chapter 12

DNA….who cares

Is used to determine

the paternity of

Children on shows such as:

Is used to catch criminals

Is used to make genetically modified food Is used to compare

similarities between species

Is used to make antibiotics and

vaccines

Page 6: DNA & Genes Chapter 12

History: Griffith and Transformation

• Year: 1928• Examined 2 strains of

pneumonia bacteria– Rough– Smooth

• Injected mice with bacteria to see if they would develop pneumonia

• Discovered transformation– Took the heat killed bacteria

and combined it with the harmless bacteria, and mice developed pneumonia

Page 7: DNA & Genes Chapter 12

History: Avery & DNA

• 1944• Used Griffith’s

experiment. He wanted to know which molecule in the heat-killed bacteria was important in transformation

• Avery used enzymes to discover that DNA was the molecule that allowed transformation to happen

Page 8: DNA & Genes Chapter 12

History: Hershey-Chase

• 1952• The Hershey-Chase experiment

used viruses known as bacteriophages.

• Question: Wanted to know which part of the virus, protein or DNA, entered the infected core of bacterium. Preformed the experiment by using radioactive markers

• Concluded, that the genetic material was DNA

Page 9: DNA & Genes Chapter 12

B. History

. CHARGAFF (1949): discovered that the % of Cytosine and Guanine were about the same in DNA; the same was true about Adenine and Thymine– This suggests BASE

PAIRING……….. that C bonds with G and A bonds with T!

Source of DNA

A T G C

Streptococcus 29.8 31.6 20.5 18.0

Yeast 31.3 32.9 18.7 17.1

Herring 27.8 27.5 22.2 22.6

Human 30.9 29.4 19.9 19.8

Phosphate group Deoxyribose

Purines Pyrimidines

Page 10: DNA & Genes Chapter 12

History (cont.)

2. Wilkins and Franklin(1952): took X-Ray photographs of DNA which suggested a twisted, helical structure, 2 strands, and bases in the center

3. Watson and Crick (1953): using all the research to date, discovered the structure for DNA: A DOUBLE HELIX (with sugar-phosphate backbones and bases on the inside held together by H bonds)

Page 11: DNA & Genes Chapter 12

More DNA info

• DNA contains information that determines an organism’s function and appearance

• Some DNA codes for proteins• DNA is located within genes

(sections of a chromosome) inside of the nucleus of every cell

Page 12: DNA & Genes Chapter 12

Wait a minute…Does that shape remind you of any other shape you may

have seen before?

How about this portion of an apple?

Page 13: DNA & Genes Chapter 12

DNA Flo Rider Featuring – T-Pain-less

Shawty got them apple bottom genes with the DNA (NA)

Nucleotides twisted that way

Next thing you know

Shawty got chro mo so o o o o omes

The A’s bond with the T’s and the C’s bond with the G’s (with the G’s)

Hydrogen bonds in the double helix

They start to fold (they start to fold)

Next thing you knowShawty got chro mo so o o o o omes

They start to fold (they start to fold)

Page 14: DNA & Genes Chapter 12

DNA Replication

• DNA opens up and makes a complete copy of itself – necessary during mitosis and meiosis

• New nucleotides float in and pair in a complementary fashion – A to T, C to G and vice versa…

Page 15: DNA & Genes Chapter 12

Figure 16.7 A model for DNA replication: the basic concept (Layer 1)

Page 16: DNA & Genes Chapter 12

Figure 16.7 A model for DNA replication: the basic concept (Layer 2)

Page 17: DNA & Genes Chapter 12

Figure 16.7 A model for DNA replication: the basic concept (Layer 3)

Page 18: DNA & Genes Chapter 12

Figure 16.7 A model for DNA replication: the basic concept (Layer 4)

Semi-conservative process…

Page 19: DNA & Genes Chapter 12

C. DNA Replication: making more DNA during the S Phase of the Cell Cycle (in the nucleus)1. The enzyme helicase unwinds DNA double helix

(breaks hydrogen bonds btwn. bases) & a replication fork is created.(Each old DNA strand will act as a template for 2 new strands to be added on)

2. Enzyme called DNA Polymerase binds to replication fork and adds free nucleotides to each old strand of DNA

3. DNA Polymerase remains attached until 2 new DNA strands are created; it “proofreads” the strands to minimize error in the process.

Page 20: DNA & Genes Chapter 12

Chromosome Structure

Chromosome

Supercoils

Coils

Nucleosome

Histones

DNA

double

helix

Go to Section:

DNA Animation

Page 21: DNA & Genes Chapter 12

DNA Replication (cont.)

• Diagram of DNA Replication:

Page 22: DNA & Genes Chapter 12

II. DNA ProteinA. RNA

• RNA: Ribonucleic Acid; used to make proteins / Single-stranded -RNA (polymer) made of nucleotides (monomer): -Ribose = 5 C sugar + Phosphate group + N Base4 bases:

• Cytosine (C)• Guanine (G)• Adenine (A)• Uracil (U) – NO THYMINE in RNA!

– 3 types of RNA: 1. messenger RNA (mRNA) – single stranded transmits info from DNA to protein syn.2. transfer RNA (tRNA) - single stranded/

20 or more varieties ea. w/ ability to bond to only 1 specific AA

3. ribosomal RNA (rRNA) – globular / major component of ribosome

Page 23: DNA & Genes Chapter 12

B. Protein Synthesis (overview)

• 2 Stages in making proteins:

1) Transcription – using DNA template to make mRNA strand

2) Translation – using mRNA strand to create polypeptides

DNA RNA ProteinTranscription Translation

Page 24: DNA & Genes Chapter 12

1. Transcription

• The Goal of Transcription is to produce a single-stranded mRNA helix that contains information from DNA to make proteins

• How it’s done: (This happens in the Nucleus!)1. DNA strand unwinds/unzips complementary DNA strands

2. Enzyme called RNA Polymerase binds to DNA “promoter” regions and “plugs in” complementary RNA nucleotides to the DNA template.

– Example = DNA Template: ATTGGCAGT

new RNA Strand: UAACCGUCA

Page 25: DNA & Genes Chapter 12

Transcription (cont.)

Page 26: DNA & Genes Chapter 12

Transcription (cont.)

3. Once produced, this pre-mRNA strand breaks away when RNA polymerase reaches a sequence of bases on DNA that act as a stop sign.

• The finished product (mRNA) moves out of the Nucleus through a nuclear pore into the cytoplasm.

4. 2 DNA complementary strands rejoin

Page 27: DNA & Genes Chapter 12

2. The Genetic Code

• How do we get proteins from mRNA strands?

• The mRNA strand must be read in groups of 3 nucleotides, called a CODON.

• Different Codons translate for different Amino acids.

Page 28: DNA & Genes Chapter 12

Codons in mRNA

Page 29: DNA & Genes Chapter 12

Codons in mRNA

• “Start” codon = AUG (Methionine)

• “Stop” codons = UAA, UAG, and UGA

• Example:• mRNA Strand:

• U-C-A-U-G-G-G-C-A-C-A-U-G-C-U-U-U-U-G-A-G

methionine glycine threonine cysteine phenylalanine STOP

Page 30: DNA & Genes Chapter 12

3. Translation

• The Goal of Translation is to “translate” these mRNA codons into their amino acids to form a polypeptide.

• How it’s done:1. mRNA strand attaches to a ribosome (rRNA)2. Each mRNA codon passes through ribosome3. Free-floating Amino Acids from cytosol are brought to

ribosome by tRNA4. Each tRNA has an anticodon to match up to mRNA codons5. Amino Acids are joined as tRNA keeps bringing them6. Polypeptide chain grows until “stop” codon is reached

Page 31: DNA & Genes Chapter 12

Translation (cont.)

• Translation

1st. mRNA strand attaches to a ribosome (rRNA)

Page 32: DNA & Genes Chapter 12

Translation (cont.)

• Translation

2nd, Each mRNA codon passes through ribosome

Page 33: DNA & Genes Chapter 12

Translation (cont.)

• Translation

3rd, Free-floating Amino Acids from cytosol are brought to ribosome by tRNA

Page 34: DNA & Genes Chapter 12

Translation (cont.)

• Translation

4th, Each tRNA has an anticodon to match up to mRNA codons

Page 35: DNA & Genes Chapter 12

Translation (cont.)

• Translation

5th, Amino Acids are joined as tRNA keeps bringing them

Page 36: DNA & Genes Chapter 12

Translation (cont.)

• Translation

. Polypeptide chain grows until “stop” codon is reached

Page 37: DNA & Genes Chapter 12

III. Genetic Changes: MutationsA. Types of Mutations

1. Gene Mutations: changes in nucleotides– Point Mutations

– Frameshift mutations

2. Chromosome Mutations: changes in # or structure of chromosome– Deletion

– Insertion/Duplication

– Inversion

– Translocation

Page 38: DNA & Genes Chapter 12

1. Gene Mutations

a. Point Mutation: the substitution, addition or removal of a single nucleotide

b. Frameshift Mutations: types of point mutations that shift the “reading frame” of the genetic message

Page 39: DNA & Genes Chapter 12

Example of Point Mutation

*image borrowed from www.science.ngfn.de/6_164.htm

Induced Point mutation in growth hormone gene causes semi-dominant dwarfism & obesity

Page 40: DNA & Genes Chapter 12

B. Chromosome Mutations

1. Deletion……………………………

2. Insertion/Duplication…………

3. Inversion…………………………

4. Translocation…………………….

Page 41: DNA & Genes Chapter 12

• A chromosomal mutation involves changes in the number or structure of chromosomes. Chromosomal mutations may change the locations of genes on chromosomes and even the number of copies of some genes.

• Deletion involves the loss of all or part of a chromosome.

• The opposite of a deletion is a • Duplication, in which a segment of a chromosome is

repeated. • When part of a chromosome becomes oriented in the

reverse of its usual direction, the result is an Inversion. • A Translocation occurs when part of one

chromosome breaks off and attaches to another, non-homologous, chromosome. In most cases, nonhomologous chromosomes exchange segments so that two translocations occur at the same time.

Page 42: DNA & Genes Chapter 12

• A chromosomal mutation involves changes in the number or structure of chromosomes. Chromosomal mutations may change the locations of genes on chromosomes and even the number of copies of some genes.

• Deletion involves the loss of all or part of a chromosome.

• The opposite of a deletion is a • Duplication, in which a segment of a chromosome is

repeated. • When part of a chromosome becomes oriented in the

reverse of its usual direction, the result is an Inversion. • A Translocation occurs when part of one

chromosome breaks off and attaches to another, non-homologous, chromosome. In most cases, nonhomologous chromosomes exchange segments so that two translocations occur at the same time.

Page 43: DNA & Genes Chapter 12

Gene Regulation in Prokaryotes

• In the absence of lactose, the repressor protein binds to the operator on DNA and inhibits transcription of lactose-processing enzymes.

• In the presence of lactose, the repressor is inhibited from binding with the operator; this all ows transcription to take place to produce lactose-processing enzymes.

The lac operon enables the production of lactose-processing enzymes in E. coli, but only when needed.