Bell Ringer 3/22/11Bell Ringer 3/22/11

Take note packet and worksheet from front Take note packet and worksheet from front tabletable

Turn in HW and permission slips/$Turn in HW and permission slips/$Respond to the following:Respond to the following: Which is more detrimental (harmful), a Which is more detrimental (harmful), a

frameshift mutation or a point mutation frameshift mutation or a point mutation and and whywhy??

What is a mutagen? Give one example.What is a mutagen? Give one example.

MUTATIONS & MUTATIONS & HUMAN GENETICSHUMAN GENETICSChapter 11.3, Chapter 12Chapter 11.3, Chapter 12

Mutations (11.3)Mutations (11.3)

MutationMutation = change in DNA sequence = change in DNA sequence Mutations can be caused by Mutations can be caused by errorserrors in in

replicationreplication, , transcriptiontranscription, , translationtranslation, , cell cell divisiondivision, or , or external agentsexternal agents

Mutations in Mutations in reproductive cellsreproductive cells can affect can affect potential offspring potential offspring (ex: inheritable genetic (ex: inheritable genetic disorders)disorders)

Mutations in Mutations in body cellsbody cells do not get passed onto do not get passed onto offspring offspring (ex: if an individual develops skin (ex: if an individual develops skin cancer)cancer)

Types of MutationsTypes of Mutations

Point MutationsPoint Mutations = a change in a single = a change in a single DNA base pairDNA base pair

Frameshift MutationsFrameshift Mutations = a single base is = a single base is addedadded or or deleteddeleted from DNA from DNA

What do the terms “missense” and nonsense” mean? What do you notice about the amino acid each codes for?

Chromosomal MutationsChromosomal Mutations = missing or = missing or extra pieces of chromosomes, switched extra pieces of chromosomes, switched pieces, extra chromosomespieces, extra chromosomes occurs frequently in plants, “super sized occurs frequently in plants, “super sized

strawberries”strawberries” Few C.M.’s get passed onto offspring Few C.M.’s get passed onto offspring

because the zygote dies or the mature because the zygote dies or the mature offspring cannot reproduceoffspring cannot reproduce

For each #, what is different between For each #, what is different between the chromosome on the left to the one the chromosome on the left to the one on the right?on the right?

Mutation of genetic Mutation of genetic material will affect material will affect the proteins the proteins producedproduced

Polyploidy in Polyploidy in strawberriesstrawberries

Wild type Commercially propagated varieties

Each cell is 1n Each cell is 8n 8 copies of each chromosome!

Polyploidy in DianthusPolyploidy in Dianthus

Cause & RepairCause & Repair

Some mutations are spontaneousSome mutations are spontaneous MutagenMutagen = any agent that causes DNA = any agent that causes DNA

change change (ex: harmful chemicals, radiation)(ex: harmful chemicals, radiation) Cells have Cells have repair mechanismsrepair mechanisms and and

special enzymesspecial enzymes that can fix incorrect that can fix incorrect DNADNA

Prepare for notes:Prepare for notes:To start, answer the following ?s in your notes:To start, answer the following ?s in your notes:Here is the original sentence:Here is the original sentence:

THE CAT ATE THE RATTHE CAT ATE THE RATFor all questions below, show how the words in the sentence For all questions below, show how the words in the sentence

are affected.are affected.1.1. A ‘C’ is added after the 1A ‘C’ is added after the 1stst C above. C above.

2. An ‘R’ is added after the 12. An ‘R’ is added after the 1stst R above. R above.

3. The first ‘A’ is changed to an ‘S’.3. The first ‘A’ is changed to an ‘S’.

4. The first ‘R’ is changed to an ‘L’.4. The first ‘R’ is changed to an ‘L’.

5. Of the 4 changes above, which was more detrimental to 5. Of the 4 changes above, which was more detrimental to the overall meaning of the sentence?the overall meaning of the sentence?

THE CCA TAT ETH ERA T

THE CAT ATE THE RRA T

THE CST ATE THE RAT

THE CAT ATE THE LAT

DNA repairDNA repair

““Proofreading” is performed by enzymes Proofreading” is performed by enzymes like like DNA ligaseDNA ligase..

Such repair mechanisms work very Such repair mechanisms work very efficiently, although they are not perfect.efficiently, although they are not perfect.

Thus, it is still best to avoid situations that Thus, it is still best to avoid situations that would expose us to mutagens.would expose us to mutagens.

HUMAN TRAITSHUMAN TRAITS

Chapter 12, Section 1Chapter 12, Section 1

PedigreePedigree PedigreePedigree = map of inheritance of genetic traits = map of inheritance of genetic traits

from generation to generationfrom generation to generation

Female Male

Does NOT have trait

Has trait

Copy this down!

Married Offspring

Shading does NOT show dominant or recessive! ONLY the presence of the trait!

KaryotypeKaryotype

Chromosomes come in pairs, inherited from Chromosomes come in pairs, inherited from parentsparents

KaryotypeKaryotype = a chart of chromosome pairs, can = a chart of chromosome pairs, can be used to visualize be used to visualize chromosomal chromosomal abnormalitiesabnormalities Chromosomes are organized by size and Chromosomes are organized by size and

centromere locationcentromere location

Humans have Humans have 23 pairs23 pairs of chromosomes, of chromosomes, 46 46 totaltotal chromosomes chromosomes

AutosomesAutosomes = any chromosome that isn’t a = any chromosome that isn’t a sex chromosomesex chromosome In humans – Chromosome pairs 1-22In humans – Chromosome pairs 1-22

Sex ChromosomeSex Chromosome = genes that determine = genes that determine an individual’s gender an individual’s gender (X and Y)(X and Y) In humans – Chromosome pair 23In humans – Chromosome pair 23 XX = femaleXX = female XY = maleXY = male

Sex chromosomes are the last pair on the Sex chromosomes are the last pair on the karyotypekaryotype

Genetic counselingGenetic counseling Pedigree can help us understand the past Pedigree can help us understand the past

& predict the future& predict the future Thousands of genetic disorders are Thousands of genetic disorders are

inherited as simple inherited as simple recessiverecessive traitstraits from benign conditions to deadly diseasesfrom benign conditions to deadly diseases

albinismalbinism cystic fibrosiscystic fibrosis Tay sachsTay sachs sickle cell anemiasickle cell anemia PKUPKU

Genetic testingGenetic testing

sequence individual genes

Recessive diseasesRecessive diseases The diseases are recessive because the The diseases are recessive because the

allele codes for either a malfunctioning allele codes for either a malfunctioning protein or no protein at allprotein or no protein at all

Heterozygotes (Aa) Heterozygotes (Aa)

carrierscarriers

have a normal phenotype because one “normal” have a normal phenotype because one “normal” allele (the dominant one) produces enough of the allele (the dominant one) produces enough of the required proteinrequired protein

Heterozygote crossesHeterozygote crosses

Aa x AaAa x Aa

A amale / sperm

A

a

fem

ale

/ eg

gs AA

Aa aa

Aa

Aa

A

a

Aa

A

a

AA

Aa aa

Aa

Heterozygotes as carriers of recessive allelesHeterozygotes as carriers of recessive alleles

carrier

carrier disease

Cystic fibrosis (recessive)Cystic fibrosis (recessive) Primarily whites of Primarily whites of

European descentEuropean descent strikes 1 in strikes 1 in 25002500 births births

1 in 25 whites is a carrier (Aa)1 in 25 whites is a carrier (Aa)

normal allele codes for a membrane protein normal allele codes for a membrane protein that transports Clthat transports Cl-- across cell membrane across cell membrane defective or absent channels limit transport of Cldefective or absent channels limit transport of Cl-- & H & H22O O

across cell membraneacross cell membrane thicker & stickier mucus coats around cells thicker & stickier mucus coats around cells mucus build-up in the pancreas, lungs, digestive tract & mucus build-up in the pancreas, lungs, digestive tract &

causes bacterial infectionscauses bacterial infections

without treatment children die before 5; without treatment children die before 5; with treatment can live past their late 20swith treatment can live past their late 20s

Tay-Sachs (recessive)Tay-Sachs (recessive) Primarily Jews of eastern European (Ashkenazi) Primarily Jews of eastern European (Ashkenazi)

descent & Cajuns (Louisiana)descent & Cajuns (Louisiana) strikes 1 in strikes 1 in 36003600 birthsbirths

100 times greater than incidence among 100 times greater than incidence among non-Jewsnon-Jews

non-functional enzyme fails to breakdown lipids in non-functional enzyme fails to breakdown lipids in brain cellsbrain cells fats collect in cells destroying their function fats collect in cells destroying their function symptoms begin few months symptoms begin few months

after birth after birth seizures, blindness & seizures, blindness &

degeneration of muscle & degeneration of muscle & mental performance mental performance

child usually dies before 5yochild usually dies before 5yo

Sickle cell anemia Sickle cell anemia (recessive)(recessive) Primarily AfricansPrimarily Africans

strikes 1 out of strikes 1 out of 400400 African Americans African Americans high frequencyhigh frequency

caused by substitution of a single amino acid caused by substitution of a single amino acid in hemoglobinin hemoglobin

when oxygen levels are low, sickle-cell when oxygen levels are low, sickle-cell hemoglobin crystallizes into long rodshemoglobin crystallizes into long rods deforms red blood cells into deforms red blood cells into

sickle shapesickle shape sickling creates sickling creates pleiotropicpleiotropic

effects = cascade of other effects = cascade of other symptomssymptoms

Dominant HeredityDominant Heredity Caused by Caused by dominant allele dominant allele ((AA))

Freckles, Widow’s peak, Hitchhickers thumb, Freckles, Widow’s peak, Hitchhickers thumb, Huntington’s disease (brain degeneration, Huntington’s disease (brain degeneration, doesn’t appear until later in age), immunity doesn’t appear until later in age), immunity to poison ivyto poison ivy

Individual will display the Individual will display the dominant dominant phenotypephenotype if its genotype is if its genotype is heterozygousheterozygous oror homozygous dominanthomozygous dominant ((AAa or a or AAAA))

http://www.zerobio.com/drag_gr11/pedigree/pedigree_overview.htm

Huntington’s chorea Huntington’s chorea (dominant)(dominant)

Dominant inheritanceDominant inheritance repeated mutation on end of repeated mutation on end of

chromosome 4chromosome 4 mutation = CAG repeatsmutation = CAG repeats glutamine amino acid repeats in proteinglutamine amino acid repeats in protein one of 1one of 1stst genes to be identified genes to be identified

build up of “build up of “huntingtin”huntingtin” protein in brain causing cell protein in brain causing cell deathdeath memory lossmemory loss muscle tremors, jerky movementsmuscle tremors, jerky movements

““chorea”chorea”

starts at age 30-50 starts at age 30-50 early deathearly death

10-20 years after start10-20 years after start

1872

Testing…Would you

want toknow?

Genetics & cultureGenetics & culture Why do all cultures have a taboo against incest?Why do all cultures have a taboo against incest?

laws or cultural taboos forbidding marriages between laws or cultural taboos forbidding marriages between close relatives are fairly universalclose relatives are fairly universal

Fairly unlikely that 2 Fairly unlikely that 2 unrelatedunrelated carriers of same carriers of same rare harmful recessive allele will meet & materare harmful recessive allele will meet & mate but matings between but matings between close relativesclose relatives increase risk increase risk

““consanguineous” (same blood) matingsconsanguineous” (same blood) matings individuals who share a individuals who share a

recent common ancestor recent common ancestor are more likely to carry are more likely to carry same recessive allelessame recessive alleles

When Heredity When Heredity Follows Different Follows Different

RulesRules

Chapter 12, Section 2Chapter 12, Section 2

Incomplete DominanceIncomplete Dominance

Complete DominanceComplete Dominance = one allele = one allele completely completely dominates over anotherdominates over another

Incomplete DominanceIncomplete Dominance = phenotype of = phenotype of a a heterozygoteheterozygote is in between the is in between the dominant & recessive phenotypes, dominant & recessive phenotypes, appearance of a third phenotypeappearance of a third phenotype Think painting! (YY=yellow and yy=blue, Think painting! (YY=yellow and yy=blue,

what would Yy=? what would Yy=?

RR Rr Rr rr

RR

Rr Rr

rrrr

CodominanceCodominance BothBoth alleles for a gene alleles for a gene

are expressed in a are expressed in a heterozygous individualheterozygous individual

Neither allele is Neither allele is dominant or recessivedominant or recessive

Ex: Blood type (A, B, Ex: Blood type (A, B, AB, O)AB, O)

Sex Determination & Sex-Sex Determination & Sex-linked Inheritancelinked Inheritance

The 23The 23rdrd pair of chromosomes pair of chromosomes determines an individuals sexdetermines an individuals sex

Males XYMales XY, , X from mom & Y from dadX from mom & Y from dad Females XXFemales XX, , both mom & dad give an Xboth mom & dad give an X Sex-linked TraitsSex-linked Traits = traits controlled by = traits controlled by

genes on sex chromosomesgenes on sex chromosomes

Sample test for color blindnessSample test for color blindness Write down Write down

A-D and A-D and what you what you see appear see appear in each in each circle.circle.

4 Sex-Linked Traits: 4 Sex-Linked Traits:  Normal Color Normal Color

VisionVision: A: 29,  B: 45,  : A: 29,  B: 45,  C: --,  D: 26C: --,  D: 26   

Red-Green Color-Red-Green Color-BlindBlind: A: 70, B: -, C: 5, : A: 70, B: -, C: 5, D: -D: -

Red Color-blindRed Color-blind: A: : A: 70, B: -, C: 5, D: 670, B: -, C: 5, D: 6   

Green Color-BlindGreen Color-Blind::A: 70,  B: --,  C: 5,  D: 2A: 70,  B: --,  C: 5,  D: 2

Red-Green colorblindness Red-Green colorblindness Hemophilia (blood doesn’t clot properly)Hemophilia (blood doesn’t clot properly) Male Pattern BaldnessMale Pattern Baldness Duchenne Muscular Distrophy (muscular Duchenne Muscular Distrophy (muscular

degeneration leading to eventual degeneration leading to eventual paralysis)paralysis)

Majority of sex-linked traits are found on Majority of sex-linked traits are found on the X-chromosomethe X-chromosome Why do you think this might be??Why do you think this might be?? Look back in your notes to the karyotype Look back in your notes to the karyotype

that was for the male.that was for the male.

X-linked traits display X-linked traits display

more in males (1 copy more in males (1 copy

of X chrom.) of X chrom.) XXRRY or XY or XrrY in malesY in males XXRRXXRR or X or XRRXXrr or X or XrrXXrr

Polygenic InheritancePolygenic Inheritance Characteristics that are influenced by Characteristics that are influenced by

several genesseveral genes The picture toThe picture to

the right shows the right shows

3 genes affecting3 genes affecting

skin pigmentationskin pigmentation

What connection can you make to What connection can you make to latitude and skin pigmentation?latitude and skin pigmentation?