How Genes Are Expressed

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How Genes Are Expressed
BIO 100 Principles of Biology
John E.Silvius
Professor of Biology
Cedarville College
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? A Gene Question ?
IF ALL CELLS ARE FROM THE ZYGOTE HOW
CAN THEY BE SO DIFFERENT AS NOTED HERE?
How do cells become so different even in the
early embryo...
Blastocyst
leading to many different cell types in the
mature human being.



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? A Gene Question ?
Cell differentiation begins here...
CELLS FROM THE ZYGOTE HAVE THE SAME GENES,
BUT DIFFERENT GENES ARE EXPRESSED AS CELLS
DIFFERENTIATE.
Blastocyst
leading to many different cell types in the
mature human being.



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Two Separate Questions
1. How are genes expressed?
2. How is gene expression controlled?
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Review of DNA (deoxyribonucleic acid)
1. DNA is an information molecule
2. Nucleotide sequence determines code
3. GENE segment of DNA
which codes for the synthesis of
one protein molecule
4. PROTEIN chain of amino acids (20
different ones)
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How are genes expressed?
Question restated How does the DNA code
direct the sequencing of amino acids to
form a protein?
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D N A to R N A
1. DNA stays in the nucleus -- master
copy
2. mRNA (messenger RNA) a complementary copy,
moves to ribosomes to direct protein synthesis
DNA
mRNA
mRNA
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D N A to R N A
1. DNA stays in the nucleus -- master
copy
2. mRNA (messenger RNA) a complementary copy,
moves to ribosomes to direct protein synthesis
DNA
Ribosomes on E.R.
mRNA
mRNA
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D N A to R N A
1. DNA stays in the nucleus -- master
copy
2. mRNA (messenger RNA) a complementary copy,
moves to ribosomes to direct protein synthesis
3. TRANSCRIPTION RNA synthesis in nucleus
from a segment of DNA
DNA
Ribosomes on E.R.
Trans.
mRNA
mRNA
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D N A to R N A Transcription
1. DNA stays in the nucleus -- master
copy
2. mRNA (messenger RNA) a complementary copy,
moves to ribosomes to direct protein synthesis
3. TRANSCRIPTION RNA synthesis from a segment
of DNA
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D N A to R N A
1. DNA stays in the nucleus -- master
copy
2. mRNA (messenger RNA) a complementary copy,
moves to ribosomes to direct protein synthesis
3. TRANSCRIPTION RNA synthesis in nucleus
from a segment of DNA
DNA
Ribosomes on E.R.
Trans.
mRNA
mRNA
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RNA to Protein
Amino acids joined into protein polymer
mRNA strand
codons
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RNA to Protein
tRNA (transfer RNA)
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Breaking the Genetic Code
A
U
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RNA to Protein
tRNA (transfer RNA)
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RNA to Protein
Amino acids joined into protein polymer
mRNA strand
codons
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RNA to Protein
tRNA (transfer RNA)
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Breaking the Genetic Code
G
G
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RNA to Protein
tRNA (transfer RNA)
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RNA to Protein
Amino acids joined into protein polymer
mRNA strand
codons
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Summary Gene Expression
DNA
Ribosomes on E.R.
Transcription
Translation
RNA
RNA
Protein
Amino acids joined into protein polymer
To Ribosomes
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Application Pancreas Producing Insulin
TRANSCRIPTION
RIBOSOMES ON ENDOPLASMIC RETICULUM
TRANSLATION
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Application Pancreas Producing Insulin
TRANSCRIPTION
RIBOSOMES ON ENDOPLASMIC RETICULUM
TRANSLATION
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Summary Gene Expression
DNA
Ribosomes on E.R.
Transcription
Translation
RNA
RNA
Protein
Amino acids joined into protein polymer
To Ribosomes
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Can You Answer Question 1?1. How are genes
expressed?
Are You Ready for Question 2? 2. How is gene
expression controlled?