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1 Biology 3 Transcription, Translation, and Mutations Dr. Terence Lee Overview 1. DNA and RNA structure 2. DNA replication 3. Transcription makes RNA 4. Translation makes protein James Watson, Francis Crick, and Rosalind Franklin discovered the structure of DNA
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Biology 3 Transcription, Translation, and Mutations 7 Molecular Genetics... · Biology 3 Transcription, Translation, and Mutations Dr. Terence Lee ... Three types of RNA can be made:

Mar 19, 2018

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Page 1: Biology 3 Transcription, Translation, and Mutations 7 Molecular Genetics... · Biology 3 Transcription, Translation, and Mutations Dr. Terence Lee ... Three types of RNA can be made:

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Biology 3

Transcription, Translation, and

Mutations

Dr. Terence Lee

Overview

1. DNA and RNA structure

2. DNA replication

3. Transcription

– makes RNA

4. Translation

– makes protein

James Watson,

Francis Crick,

and Rosalind

Franklin

discovered the

structure of

DNA

Page 2: Biology 3 Transcription, Translation, and Mutations 7 Molecular Genetics... · Biology 3 Transcription, Translation, and Mutations Dr. Terence Lee ... Three types of RNA can be made:

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Image of DNA

DNA Structure

• Deoxyribonucleic acid (DNA) is

a type of nucleic acid

• Three parts:

1. Sugar group (deoxyribose)

2. Phosphate group

3. Nitrogenous base

• Adenine

• Guanine

• Thymine

• Cytosine

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���� DNA provides the instructions for building virtually every organism on earth!

The protein, influenced by the environment and in somecases other genes, then produces the trait.

Central Central Dogma of Biology

Page 4: Biology 3 Transcription, Translation, and Mutations 7 Molecular Genetics... · Biology 3 Transcription, Translation, and Mutations Dr. Terence Lee ... Three types of RNA can be made:

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DNA Replication

• Process by which a cell makes another copy

of its DNA

• Pairing Rules:

– A = T

– G = C

• The structure of DNA is a

double helix

• Shaped like a twisting ladder

Page 5: Biology 3 Transcription, Translation, and Mutations 7 Molecular Genetics... · Biology 3 Transcription, Translation, and Mutations Dr. Terence Lee ... Three types of RNA can be made:

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RNA Structure

• Ribonucleic acid (RNA) is a type of nucleic acid

• Three parts

1. Sugar group (ribose)

2. Phosphate group

3. Nitrogenous base

• Adenine

• Guanine

• Uracil

• Cytosine

How is RNA different from DNA?

1. Ribose has –OH group

2. RNA has uracil instead of thymine

3. RNA is a single strand

4. DNA stays in nucleus

5. RNA is made from DNA in nucleus and then

moves to cytoplasm.

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HOW GENES WORK: AN OVERVIEWTRANSCRIPTIONThe sequence for a gene is copied from DNA to a middleman molecule called mRNA.

TRANSLATIONThe sequence for a gene, now encoded in mRNA, is used to direct the production of a protein.

Inside nucleus Cytoplasm

Genes

Nuclearpore

DNAmRNA

Protein molecule

Grandmother’scookbook

Copying cookierecipe to index card

Index cardwith recipe

Chocolatechip cookies

Combining andbaking ingredient

Transcription

• Transcription is the process of using DNA

as a template to synthesize RNA.

– 1.) The DNA strands separate.

– 2.) RNA Polymerase reads the DNA and builds

the RNA strand.

– 3.) Three types of RNA can be made:

1. mRNA – messenger RNA

2. rRNA – ribosomal RNA

3. tRNA – transfer RNA

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• Promoter sequence – specific sequences of DNA that

the RNA Polymerase recognizes.

• Protein code – the DNA sequence that holds the genetic

material to create each protein.

• Termination sequence – Tells the RNA Polymerase to

stop transcription.

TRANSCRIPTION

RECOGNIZE and BINDOnce RNA polymeraserecognizes a promoter site,it binds to one strand of theDNA and begins readingthe gene’s message.

TRANSCRIBEAs the DNA strand is processed through the RNA polymerase, the RNA polymerase builds a single-strand copy of the gene, called the mRNA transcript.

TERMINATEWhen the RNA polymeraseencounters a code signalingthe end of the gene, it stopstranscription and releasesthe mRNA transcript.

CAPPING and EDITINGBefore the mRNA transcript can be translated into a protein, a cap and tail are often added for protection and to promote recognition, and non-coding sections are removed.

As the RNA polymerase moves down the strand of DNA, the helix unwinds so that the DNA can be read. At the same time, the DNA that has already been transcribed rewinds back to its original double-helix form.

UNWIND and REWIND

mRNA transcript leaves nucleus

to be translated into a protein.

RNApolymerase

DNA

mRNA

transcript

Tail

Cap Non-protein-coding

regions of mRNA

RNApolymerase

Promoter site

RNApolymerase

Termination site

mRNA transcript

Helix unwinds

Helix unwinds

21 3

4

Translation

• Translation is the process of using the information in

mRNA to direct protein synthesis.

• Relies on sets of 3 nucleotides called codons.

• Each codon codes for a specific amino acid.

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Translation

• Ribosome

– 2 subunit non-membrane

organelle

– Holds the mRNA and tRNA

during protein formation

• tRNA

– Transfer RNA

– Reads the codons and finds

the correct amino acids.

Translation

1. Initiation

2. Elongation

3. Termination

Translation

• Initiation:

1. Ribosome small subunit binds to mRNA

2. Finds the start codon

3. The tRNA binds to the codon and brings the first

amino acid

4. The large subunit joins the small subunit and

protein formation can begin.

Page 9: Biology 3 Transcription, Translation, and Mutations 7 Molecular Genetics... · Biology 3 Transcription, Translation, and Mutations Dr. Terence Lee ... Three types of RNA can be made:

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Translation

• Elongation:

1. A new tRNA arrives and reads the codon.

2. The next amino acid arrives and binds to the

previous amino acid.

3. The process continues until a polypeptide

(protein) is formed.

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Translation

• Termination:

– Occurs when the ribosome reaches a stop codon.

– The two subunits come apart.

– The mRNA is released.

Summary of Protein Synthesis

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5.4 Not all DNA contains instructions for making proteins.

The Proportion of the DNA That Codes for Genes

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Introns and Exons

• Portions of the mRNA are removed before

translation.

Mutations

• Point Mutation – change in a single nucleotide of the

DNA sequence.

• Insertions and Deletions – changes one or more

nucleotides in the DNA sequence.

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A “fast-flush”

response