Biology 3 Transcription, Translation, and Mutations

[Pages:13]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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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!

CCeenntratlral Dogma of Biology

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

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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

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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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Inside nucleus DNA

HOW GENES WORK: AN OVERVIEW

TRANSCRIPTION

The sequence for a gene is copied from DNA to a middleman molecule called mRNA.

Cytoplasm mRNA

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

Genes

Nuclear pore

Protein molecule

Grandmother's cookbook

Copying cookie recipe to index card

Index card with recipe

Combining and baking ingredient

Chocolate chip cookies

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.

DNA

TRANSCRIPTION

1 RECOGNIZE and BIND Once RNA polymerase recognizes a promoter site, it binds to one strand of the DNA and begins reading the gene's message. RNA polymerase

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

RNA polymerase

3 TERMINATE When the RNA polymerase encounters a code signaling the end of the gene, it stops transcription and releases the mRNA transcript.

RNA polymerase

Promoter site

mRNA transcript

Termination site mRNA transcript

UNWIND and REWIND 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.

Helix unwinds

Helix unwinds

4 CAPPING and EDITING

Before the mRNA

transcript can be

Tail

translated into a protein,

a cap and tail are often

Cap

Non-protein-coding regions of mRNA

added for protection and to promote recognition,

and non-coding sections

are removed.

mRNA transcript leaves nucleus to be translated into a protein.

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.

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