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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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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.


  • 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.


Harmless bacteria (rough colonies)

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

Lives


Heat-killed disease-causing bacteria (smooth colonies)

Lives


Heat-killed disease-causing bacteria (smooth colonies) He then injected the heat-killed bacteria into the mice. The mice survived.

  • 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


Heat-killed disease-causing bacteria (smooth colonies) He then injected the heat-killed bacteria into the mice. The mice survived.

  • 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


  • Transformation  He then injected the heat-killed bacteria into the mice. The mice survived.

    • 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 He then injected the heat-killed bacteria into the mice. The mice survived.

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


History of dna research2
History of DNA Research He then injected the heat-killed bacteria into the mice. The mice survived.

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 He then injected the heat-killed bacteria into the mice. The mice survived.

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


DNA He then injected the heat-killed bacteria into the mice. The mice survived.

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


Dna structure
DNA Structure He then injected the heat-killed bacteria into the mice. The mice survived.

  • DNA is made up of nucleotides.

Nitrogenous

Base

Phosphate

Sugar


Parts of a nucleotide
Parts of a nucleotide He then injected the heat-killed bacteria into the mice. The mice survived.

  • 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 He then injected the heat-killed bacteria into the mice. The mice survived.

  • 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


Guanine He then injected the heat-killed bacteria into the mice. The mice survived.

Cytosine

Adenine

Thymine


  • Double Helix He then injected the heat-killed bacteria into the mice. The mice survived.

    • 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 Double Helix He then injected the heat-killed bacteria into the mice. The mice survived.



DNA base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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 must base pairs. How does so much DNA fit in every tiny cell in your body?condense (make itself smaller) by folding itself around proteins called Histones.

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


  • 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: base pairs. How does so much DNA fit in every tiny cell in your body?

Histone

DNA

Double Helix

Chromatin

DNA around histones


Chromosomes
Chromosomes base pairs. How does so much DNA fit in every tiny cell in your body?

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

  • See Fig. 12-10 in your book.


DNA base pairs. How does so much DNA fit in every tiny cell in your body?

Double Helix

Chromosomes

Made up of chromatin

Chromatin

DNA around histones

Histone =


  • DNA Double Helix base pairs. How does so much DNA fit in every tiny cell in your body? Chromatin  Chromosome

DNA Double Helix

DNA Chromatin

DNA Chromosome

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


Dna replication
DNA Replication base pairs. How does so much DNA fit in every tiny cell in your body?

  • Occurs when cells divide.

    (Cell division)


Dna replication1
DNA Replication base pairs. How does so much DNA fit in every tiny cell in your body?

  • DNA makes an exact copy of itself

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


Replication
Replication base pairs. How does so much DNA fit in every tiny cell in your body?

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


phosphate base pairs. How does so much DNA fit in every tiny cell in your body?

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 base pairs. How does so much DNA fit in every tiny cell in your body?

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 base pairs. How does so much DNA fit in every tiny cell in your body?

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 base pairs. How does so much DNA fit in every tiny cell in your body?


Replication2
Replication base pairs. How does so much DNA fit in every tiny cell in your body?

  • Template Strand (original)

  • CGTATCCGGAATTT

  • The complimentary strand..

  • GCATAGGCCTTAAA


Template strand base pairs. How does so much DNA fit in every tiny cell in your body?

Complimentary Strand

ACGGCAT

TACGGCAT

TGCCGTA

ATGCCGTA


Complimentary
Complimentary base pairs. How does so much DNA fit in every tiny cell in your body?

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

  • CAT

GTA


RNA base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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)


Base-pairing in RNA base pairs. How does so much DNA fit in every tiny cell in your body?

1) A always pairs with U

2) C always pairs with G


Types of rna
Types of RNA base pairs. How does so much DNA fit in every tiny cell in your body?


Compare dna and rna
Compare DNA and RNA base pairs. How does so much DNA fit in every tiny cell in your body?

1) Sugars are different:

DeoxyriboseRibose

H OH OH OH

H OH OH OH


Compare dna and rna1
Compare DNA and RNA base pairs. How does so much DNA fit in every tiny cell in your body?

DNA RNA

2) A, G, C,T A, G, C, U

(A–T, C-G) (A-U, C-G)

3) Double stranded Single stranded

4) only 1 type 3 types


Protein
Protein base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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 base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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.



  • What is base pairs. How does so much DNA fit in every tiny cell in your body?transcription?

    • The process where mRNA is made from a DNA template

    • Transcription happens in the nucleus


  • What is base pairs. How does so much DNA fit in every tiny cell in your body?translation?

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

    • Translation takes place on ribosomes in the cytoplasm


Transcription Translation base pairs. How does so much DNA fit in every tiny cell in your body?


Transcription
Transcription base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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 base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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.


Bases base pairs. How does so much DNA fit in every tiny cell in your body?

DNA

mRNA


Post transcriptional modification
Post-transcriptional modification base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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 base pairs. How does so much DNA fit in every tiny cell in your body?

E I E I E

initial DNA

 introns cleaved

pre-mRNA

 exons combine

final mRNA


Now look at the right side of the picture. base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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


  • A (E) tRNA approaches the ribosome. base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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


  • This occurs according to base pairing. base pairs. How does so much DNA fit in every tiny cell in your body?

  • 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.



Codon chart
Codon Chart resulting strand is a protein.

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

CODONAMINO ACID

AGU

AGC

GGU


  • What are mutations? resulting strand is a protein.

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


Types of mutations: resulting strand is a protein.

  • Gene mutations result from changes in a single gene

  • Chromosomal mutations involve changes in whole chromosomes


  • Gene mutations: resulting strand is a protein.

    • 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 resulting strand is a protein.

One base change


Insertions
Insertions resulting strand is a protein.

Many base changes


Deletions
Deletions resulting strand is a protein.


  • Chromosomal mutations resulting strand is a protein.:

    • Include deletions, duplications, inversions, and translocations.


  • Deletions resulting strand is a protein. involve the loss of all or part of a chromosome.


  • Duplications resulting strand is a protein. produce extra copies of parts of a chromosome.


  • Inversions resulting strand is a protein. reverse the direction of parts of chromosomes.


  • Translocations resulting strand is a protein. occurs when part of one chromosome breaks off and attaches to another.


  • Significance of Mutations resulting strand is a protein.

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

    • Some mutations are the cause of genetic disorders.


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