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GENEGENE EXPRESSION:EXPRESSION:

Individuality and Individuality and

ExpressionExpression HOW DOES DNA KNOW WHEN HOW DOES DNA KNOW WHEN

TO MAKE A PROTEIN?TO MAKE A PROTEIN?

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Genes: The Video ClipGenes: The Video Clip

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DNA and IndividualityDNA and IndividualityAre all genes turned on in all cells?Are all genes turned on in all cells?

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The answer isThe answer is NO!NO!

• Every body cell contains all DNA

• Cells “use” only genes specific for function

– EX. Red blood cells use only genes that make it carry oxygen

– Can you list more examples?• Enzymes, insulin, cell membrane, hair, muscles

• **THEREFORE, NOT ALL DNA IS EXPRESSED (MADE INTO PROTEIN) IN EVERY CELL!**

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MUTATIONSMUTATIONSWhen DNA goes bad When DNA goes bad

Mutations to control genes can transform one body part into another. Scientists have studied flies carrying Hox mutations that sprout legs on their foreheads instead of antennae!

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Mutation: The Video ClipMutation: The Video Clip

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IMPORTANT FACT!IMPORTANT FACT!

MUTATIONS MUST OCCUR IN SEX CELLS IN ORDER

FOR THEM TO BE PASSED ON TO NEXT GENERATION!!!!!!!!!!

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Gene Mutations1. Change in DNA sequence which effect genetic

information and traits– one nitrogen base is affected

2. When do mutations occur? During replication (meiosis / mitosis) and protein synthesis

• **Review** What does DNA ultimately code for?Proteins

3. Is construction of protein based on original DNA strand?

Yes! (b/c it is what codes for mRNA)

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Gene Mutations con’t…Gene Mutations con’t…4. What would happen to protein made if

DNA sequence was changed?– Wrong protein made– Wrong shape of protein

• This would make protein unusable

Normal red blood cells (top)

and sickle cells (bottom)

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DNA fails to copy accurately

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D. Types of Gene MutationsD. Types of Gene Mutations

1.1. POINTPOINT MUTATION: MUTATION: CHANGECHANGE:: Base isBase is switched from one point to anotherswitched from one point to another

EXAMPLEEXAMPLE:: CTCCTC on DNA makes on DNA makes GAG GAG for mRNA mRNA – GAGGAG codes for codes for GLUGLU

» If If TT changed to changed to GG, would have, would have GUG GUG on mRNA on mRNA » This codes forThis codes for VALVAL

RESULTRESULT: Wrong: Wrong AMINO ACIDAMINO ACID is coded for is coded for which means, wrongwhich means, wrong PROTEINPROTEIN is madeis made

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2.2. FRAME-SHIFT FRAME-SHIFT Mutation: Mutation: CHANGECHANGE: base is either: base is either deleted or addeddeleted or added EXAMPLEEXAMPLE:: TCA TTT on DNA; TCA TTT on DNA;

• AGU-AAA on mRNA codes forAGU-AAA on mRNA codes for Ser + LysSer + Lys• If theIf the T is deletedT is deleted in the DNA, the mRNA would in the DNA, the mRNA would

now readnow read GUA AAGUA AA• tRNA will read “tRNA will read “GUA”GUA” first which codes forfirst which codes for ValVal• Similar results if a base isSimilar results if a base is addedadded

RESULTRESULT:: Wrong Wrong AMINO ACIDAMINO ACID is coded for = wrongis coded for = wrong PROTEINPROTEIN is made OR Translation willis made OR Translation will abruptlyabruptly STOP

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DeletionDeletion

DuplicationDuplication

InversionInversion

Translocation

 

E. Chromosomal Mutations

Match the terms with the diagrams : Inversion, Translocation, Duplication, Deletion

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Mutation Problems Affecting Humans:

A. Non-Disjunction- _____________________________________________

1. causes this: ______________________________________________

2. chromosome # in a normal cell: _____

chromosome # in a non-disjunction cell: ______

3. common name of disorder in human: ___________________________

results in: ________________________________________________

An extra chromosome at location # ____

chromosome pairs don’t separate

an extra chromosome in the cell

4647

Down Syndrome

mental retardation and distinguishing facial features

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DOWN SYNDROME MALEDOWN SYNDROME MALE

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B. PKU : _______________________________________________

1. cause: _______________________________________________

2. problem: _____________________________________________

3. symptoms: ____________________________________________

4. controlled by: __________________________________________

Phenylketonuria

gene which controls the breakdown of phenylalanine is missing

Phenylalanine builds up to toxic levels

Mental retardation or death

Eliminating phenylalanine from your diet

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C. Sickle Cell Anemia ________________________________________

1. cause: ________________________________________________

2. problem : ______________________________________________

3. symptoms: ________________________________________

Red blood cells become sickle shaped

A mutated hemoglobin gene

red blood cells can’t carry oxygen; stick into blood vessels

Lack of oxygen, weakness, pain

Normal Cell Sickle Cell

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• Human Chromosomes (Human Chromosomes (4646 in a in a normal human cell!)normal human cell!)

• Two types:Two types:a)a) Normal Normal chromosomes:chromosomes: 44 44 in eachin each BODYBODY

CELL;CELL; 2222 in eachin each GAMETEGAMETE ((sexsex cell)cell)

b)b) SexSex chromosomes:chromosomes: 2 2 in eachin each BODY BODY CELL;CELL;

11 in eachin each GAMETE GAMETE ((sex sex cell)cell)• MALE:MALE: X and YX and Y• FEMALE:FEMALE: X and XX and X

G. Determining Sex

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Chances for having a boy or girl? Chances for having a boy or girl? 50% OF COURSE…LET’S SEE!50% OF COURSE…LET’S SEE!

XX YY

XX

XX

XXXX

XXXX XXYY

XXYY

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Human Karyotype Arrangement

human male

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H. Environmental H. Environmental ExpressionExpression

Some genes are “Some genes are “turned onturned on” ” under certain under certain environmentalenvironmental conditionsconditions

• EX. Himalayan Rabbit:EX. Himalayan Rabbit: Fur Fur changes color due tochanges color due to TEMPERATURETEMPERATURE changechange– WARMWARM = = White fur (no pigment White fur (no pigment

produced)produced)– COLD COLD == Black furBlack fur Why does Why does

this make sense?this make sense?• Because black absorbs the heat,

helping little bunny rabbit to stay warm

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I. Summary of MutationsI. Summary of Mutations

• Must occur inMust occur in sex cellssex cells to be passed onto be passed on• Not all mutations areNot all mutations are bad bad (depends on(depends on

environmentenvironment))• Ultimate source ofUltimate source of variation variation within a within a

species!!!!!!species!!!!!!– Take humans for instance….do we all look Take humans for instance….do we all look

the same????????? the same????????? NO!!!!!!NO!!!!!!

• Caused byCaused by::– Exposure toExposure to radiationradiation (ex.(ex. UVUV Rays)Rays)– Exposure to certainExposure to certain chemicals chemicals (in cigarettes, (in cigarettes,

emitted from factories)emitted from factories)

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• How do we know that traits and diseases are genetically related?

• The Human Genome Project

1) What is it? _______________________________________________

2) Why do it? _______________________________________________

3) How far along are we? _____________________________________

Project to identify the location of 30,000 genes

To identify the locations of genetic diseases and possibly control/eliminate them

the map was completed in 2004

III. The Human GenomeIII. The Human Genome

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The Code of Life video• Getting the Letters Out (5:52)• One Wrong Letter (8:57)• Finding Cures is Hard (8:07)• Finding Disease Genes (4:06)• DNA Databases (4:14)• A Family Disease (8:05)• Genetic Modification (4:27)

• NOVA Online | Cracking the Code of Life | Watch the Program

• Let’s watch: Genetic Modificationhttp://NOVA Online | Cracking the Code of Life | Watch the Program