Dna protein synthesis
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DNA / Protein Synthesis. History of DNA Research. DNA – Deoxyribonucleic acid 1) Frederick Griffith (1928)- discovered that a factor in heat-killed, disease-causing bacteria can “transform” harmless bacteria into ones that can cause disease. Griffith's Experiments

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DNA / Protein Synthesis

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Dna protein synthesis

DNA / Protein Synthesis


History of dna research

History of DNA Research

DNA – Deoxyribonucleic acid

1) Frederick Griffith (1928)- discovered that a factor in heat-killed, disease-causing bacteria can “transform” harmless bacteria into ones that can cause disease.


Dna protein synthesis

  • Griffith's Experiments

    • Griffith set up four individual experiments.

    • Experiment 1: Mice were injected with the disease-causing strain of bacteria. The mice developed pneumonia and died.


Dna protein synthesis

Harmless bacteria (rough colonies)

  • Experiment 2: Mice were injected with the harmless strain of bacteria. These mice didn’t get sick.

Lives


Dna protein synthesis

  • Experiment 3: Griffith heated the disease-causing bacteria. He then injected the heat-killed bacteria into the mice. The mice survived.

Heat-killed disease-causing bacteria (smooth colonies)

Lives


Dna protein synthesis

Heat-killed disease-causing bacteria (smooth colonies)

  • Experiment 4: Griffith mixed his heat-killed, disease-causing bacteria with live, harmless bacteria and injected the mixture into the mice. The mice developed pneumonia and died.

Harmless bacteria (rough colonies)

Live disease-causing bacteria(smooth colonies)

Dies of pneumonia


Dna protein synthesis

Heat-killed disease-causing bacteria (smooth colonies)

  • Griffith concluded that the heat-killed bacteria passed their disease-causing ability to the harmless strain.

Harmless bacteria (rough colonies)

Live disease-causing bacteria(smooth colonies)

Dies of pneumonia


Dna protein synthesis

  • Transformation 

    • Griffith called this process transformation because one strain of bacteria (the harmless strain) had changed permanently into another (the disease-causing strain).

    • Griffith hypothesized that a factor must contain information that could change harmless bacteria into disease-causing ones.


History of dna research1

History of DNA Research

2) Oswald Avery (1944)- discovered DNA was responsible for transformation


History of dna research2

History of DNA Research

3) Hershey and Chase (1952)- their studies supported Avery’s work by studying bacteriophage (a virus that infects bacteria)


History of dna research3

History of DNA Research

4) Watson and Crick (1953)- first to develop a double-helix model of DNA


Dna protein synthesis

DNA

  • DNA is found inside the nucleus of every cell in your body


Dna structure

DNA Structure

  • DNA is made up of nucleotides.

Nitrogenous

Base

Phosphate

Sugar


Parts of a nucleotide

Parts of a nucleotide

  • A nucleotide contains three parts:

    1) Phosphate group

    2) 5-carbon sugar group (deoxyribose)

    3) Nitrogenous bases (4 types)

    • Adenine (A)

    • Guanine (G) Purines (double rings)

    • Cytosine (C)

    • Thymine (T) Pyrimidines (single ring)

To help you remember:

CUT = PY


Chargaff s rule

Chargaff’s Rule

  • Erwin Chargaff (1949) discovered the base-pairing rules for nitrogenous bases:

    1) A always pairs with T

    C always pairs with G

    2) % A in DNA = % T in DNA

    % C in DNA = % G in DNA


Dna protein synthesis

Guanine

Cytosine

Adenine

Thymine


Dna protein synthesis

  • Double Helix

    • DNA molecule is composed of two long chains of nucleotides twisted and held together by hydrogen bonds in the center between the nitrogen bases


Dna protein synthesis

  • DNA Double Helix


Dna protein synthesis

  • In even in your smallest chromosome there are 30 million base pairs. How does so much DNA fit in every tiny cell in your body?


Dna protein synthesis

DNA

  • You fold it!

  • Think about how much easier it is to pack your suitcase when everything is nicely folded.

Can’t fit

Much more fits when you organize and fold it.


Dna protein synthesis

  • DNA must condense (make itself smaller) by folding itself around proteins called Histones.

  • When DNA wraps around Histones it forms tight coils and is called chromatin.


Dna protein synthesis

  • What are histones?

  • Histones are proteins that DNA wraps around.

  • What is Chromatin?

  • Chromatin is what you call DNA when it is wrapped around the Histones.


Example

Example:

Histone

DNA

Double Helix

Chromatin

DNA around histones


Chromosomes

Chromosomes

  • When the chromatin forms coils and condenses it forms a chromosome.

  • See Fig. 12-10 in your book.


Dna protein synthesis

DNA

Double Helix

Chromosomes

Made up of chromatin

Chromatin

DNA around histones

Histone =


Dna protein synthesis

  • DNA Double Helix  Chromatin  Chromosome

DNA Double Helix

DNA Chromatin

DNA Chromosome

http://www.biostudio.com/demo_freeman_dna_coiling.htm (dna coiling)


Dna replication

DNA Replication

  • Occurs when cells divide.

    (Cell division)


Dna replication1

DNA Replication

  • DNA makes an exact copy of itself

  • takes place inside the nucleus during S phase before cell division


Replication

Replication

  • Each strand of the double helix of DNA serves as a template against which the new strand is made.


Dna protein synthesis

phosphate

Sugar-phosphate

Sugar-phosph

DNA Base Pairing Rules

  • A compliments T

  • T compliments A

  • G compliments C

  • C compliments G

G

A

C

T

T

C

A

A

G

T


Replication1

Replication

Step 1: The hydrogen bonds between the double helix break and two strands separate. Each strand is called a template strand.

Step 2: Two new complementary strands are formed following the rules of base pairing. The new strands are called complimentary strands.

Template strand

Compliment strand


How dna replication works

DNA Polymerase

A

T

How DNA Replication Works!

DNA polymerase is an enzyme that adds the complimentary bases to the DNA template strand and also “proofreads” or checks that it is correct.


Semiconservative

Semiconservative


Replication2

Replication

  • Template Strand (original)

  • CGTATCCGGAATTT

  • The complimentary strand..

  • GCATAGGCCTTAAA


Dna protein synthesis

Template strand

Complimentary Strand

ACGGCAT

TACGGCAT

TGCCGTA

ATGCCGTA


Complimentary

Complimentary

  • If I have a strand that DNA sequence of CAT what would be on the complimentary strand?

  • CAT

GTA


Dna protein synthesis

RNA

  • Ribonucleic acid

  • Single strand

  • made up of nucleotides

  • contains three parts:

    • 1) Phosphate group

    • 2) 5-carbon sugar group (ribose)

    • 3) Nitrogenous bases (4 types)

      • Adenine (A)

      • Guanine (G) Purines (double rings)

      • Cytosine (C)

      • Uracil (U) Pyrimidines (single ring)


Dna protein synthesis

Base-pairing in RNA

1) A always pairs with U

2) C always pairs with G


Types of rna

Types of RNA


Compare dna and rna

Compare DNA and RNA

1) Sugars are different:

DeoxyriboseRibose

H OH OH OH

HOH OH OH


Compare dna and rna1

Compare DNA and RNA

DNARNA

2) A, G, C,TA, G, C, U

(A–T, C-G) (A-U, C-G)

3) Double strandedSingle stranded

4) only 1 type3 types


Protein

Protein

  • Proteins are made of building blocks called amino acids.

  • Proteins are different from one another by the sequence, or order, of their amino acids.


Protein1

Protein

  • There are 20 different amino acids.

  • Thousands of proteins can be made from these amino acids because there are many different orders that they can be in.


Dna protein synthesis

  • Proteins are made in two steps:

    • Transcription

    • Translation


Dna protein synthesis

  • What is transcription?

    • The process where mRNA is made from a DNA template

    • Transcription happens in the nucleus


Dna protein synthesis

  • What is translation?

    • Translation is the decoding of an mRNA message into a protein.

    • Translation takes place on ribosomes in the cytoplasm


Dna protein synthesis

Transcription Translation


Transcription

Transcription

  • Protein synthesis begins when a strand of (A) DNA unravels.

  • The code for producing a protein is carried in the sequence of the (B) bases in the DNA.

  • Each group of three bases forms a codon, which represents a particular amino acid.


Transcription1

Transcription

  • One of the unwound strands of DNA forms a complementary strand called (C) mRNA.

  • This process is called transcription.

  • It takes place in the nucleus of the cells.


Dna protein synthesis

Bases

DNA

mRNA


Post transcriptional modification

Post-transcriptional modification

  • DNA is composed of coding and noncoding sequences

  • Noncoding region = Introns

  • Coding region = Exons (code for proteins)

  • During transcription, introns are cleaved and removed, while exons combine to form useful mRNA


Post transcriptional modification1

Post-transcriptional modification

E I E I E

initial DNA

 introns cleaved

pre-mRNA

 exons combine

final mRNA


Dna protein synthesis

Now look at the right side of the picture.

  • The mRNA has moved into the cytoplasm, where it attaches to a (D) ribosome.

  • A phase of protein synthesis called translation then begins.

Ribosome

mRNA


Dna protein synthesis

  • A (E) tRNA approaches the ribosome.

  • At one end of this molecule are three bases known as an (F) anticodon.

  • At the ribosome, each anticodon lines up with its complementary codon on the mRNA.

tRNA

Anticodon

Codon

Anticodon


Dna protein synthesis

  • This occurs according to base pairing.

  • At the other end of tRNA, an (G) amino acid is attached.

  • As the ribosome moves along the strand of mRNA, new tRNAs are attached.

  • This brings the amino acids close to each other.


Dna protein synthesis

  • The amino acids are joined by peptide bonds, and the resulting strand is a protein.


Codon chart

Codon Chart

  • To determine which amino acid we choose we use this chart:

CODONAMINO ACID

AGU

AGC

GGU


Dna protein synthesis

  • What are mutations?

    • Mutations are changes in the DNA sequence that affects the genetic information


Dna protein synthesis

Types of mutations:

  • Gene mutations result from changes in a single gene

  • Chromosomal mutations involve changes in whole chromosomes


Dna protein synthesis

  • Gene mutations:

    • Point mutations – affect only one nucleotide because they occur at a single point

      • Include substitutions, additions, and deletions

    • Frameshift mutations – when a nucleotide is added or deleted and bases are all shifted over, leaving all new codons.

      • Include additions and deletions

      • Substitutions don’t usually cause a frameshift


Substitutions

Substitutions

One base change


Insertions

Insertions

Many base changes


Deletions

Deletions


Dna protein synthesis

  • Chromosomal mutations:

    • Include deletions, duplications, inversions, and translocations.


Dna protein synthesis

  • Deletions involve the loss of all or part of a chromosome.


Dna protein synthesis

  • Duplications produce extra copies of parts of a chromosome.


Dna protein synthesis

  • Inversions reverse the direction of parts of chromosomes.


Dna protein synthesis

  • Translocations occurs when part of one chromosome breaks off and attaches to another.


Dna protein synthesis

  • Significance of Mutations

    • Many mutations have little or no effect on gene expression.

    • Some mutations are the cause of genetic disorders.


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