The Human The Human GenomeGenome

Chapter 14Chapter 14

Human HeredityHuman HeredityHuman Human

chromosomeschromosomes KaryotypeKaryotype – a – a

picture of picture of chromosomes chromosomes arranged in pairsarranged in pairs

Human HeredityHuman Heredity

Human HeredityHuman Heredity Human bodyHuman body

• 46 chromosomes46 chromosomesHaploidHaploid sperm cell sperm cell

with 23 with 23 chromosomeschromosomes

HaploidHaploid egg cell with egg cell with 23 chromosomes23 chromosomes

They form a They form a diploiddiploid zygote or fertilized zygote or fertilized egg cell with 46 egg cell with 46 chromosomeschromosomes

Human HeredityHuman Heredity Sex chromosomesSex chromosomes

• 2 of the 46 2 of the 46 chromosomeschromosomes

• Determine the sex Determine the sex of that personof that person

Females have X Females have X and X or XX and X or XX chromosomeschromosomes

Males have X and Y Males have X and Y or XY chromosomesor XY chromosomes

Human HeredityHuman Heredity Autosomes Autosomes

(Autosomal (Autosomal Chromosomes)Chromosomes)• The other 44 The other 44

chromosomes found chromosomes found in all body cellsin all body cells

• These are the These are the chromosomes chromosomes separate from the separate from the sex cellssex cells

• Typically numbered Typically numbered on a karyotypeon a karyotype

Human HeredityHuman Heredity Human traitsHuman traits

Pedigree chartPedigree chart – Shows the – Shows the relationship relationship within a familywithin a family• Shows how traits Shows how traits

may be passed may be passed through through generationsgenerations

Human HeredityHuman HeredityHuman genesHuman genes

Blood group genesBlood group genes• Rh blood groupsRh blood groups

Positive and Positive and negativenegative

Rh+ is dominantRh+ is dominant• ABO blood groupsABO blood groups

IA, I B, and iIA, I B, and i IA and I B are IA and I B are

codominantcodominant

Human HeredityHuman Heredity Recessive allelesRecessive alleles

• Genetic disorders Genetic disorders usually are not usually are not discovered until seen discovered until seen in the environmentin the environment

Dominant allelesDominant alleles• Anyone having Anyone having

carrying an allele will carrying an allele will have the disorderhave the disorder

Codominant allelesCodominant alleles

Human HeredityHuman Heredity From gene to From gene to

moleculemolecule Cystic fibrosisCystic fibrosis

• Common in people Common in people from northern Europefrom northern Europe

• Serious digestive and Serious digestive and breathing problemsbreathing problems

• Caused by the Caused by the deletion of just one deletion of just one amino acidamino acid

Human HeredityHuman Heredity Sickle cell diseaseSickle cell disease

• Blood cells doughnut Blood cells doughnut or comma shapedor comma shaped

• Heterozygous Heterozygous people don’t contract people don’t contract malariamalaria

• Humans with all Humans with all sickle celled blood sickle celled blood can diecan die

• Why do so many Why do so many African Americans African Americans have sickle celled have sickle celled blood?blood?

14-2 Human Chromosomes14-2 Human ChromosomesHuman genes and Human genes and

chromosomeschromosomes One cell has 6 One cell has 6

billion base pairs or billion base pairs or A,C,T,& GA,C,T,& G

46 Chromosomes 46 Chromosomes are found in every are found in every diploid human celldiploid human cell

14-2 Human Chromosomes14-2 Human Chromosomes Only 2% of all DNA Only 2% of all DNA

is used for genes or is used for genes or transcribed into transcribed into RNARNA

Average genes are Average genes are 3,000 base pairs3,000 base pairs

Largest gene is 2 Largest gene is 2 million base pairsmillion base pairs

14-2 Human Chromosomes14-2 Human Chromosomes Chromosomes 21 Chromosomes 21

and 22 are the and 22 are the smallestsmallest• 22 has 545 genes (43 22 has 545 genes (43

million base pairs)million base pairs)• 21 has 225 genes (21 21 has 225 genes (21

million base pairs)million base pairs) Lou Gehrig’s Disease Lou Gehrig’s Disease

or Amyotrophic or Amyotrophic Lateral Lateral Sclerosis(ALS)Sclerosis(ALS)

14-2 Human Chromosomes14-2 Human Chromosomes Sex-linked genesSex-linked genes – –

genes located on the genes located on the sex chromosomessex chromosomes ColorblindnessColorblindness

• Red-green Red-green colorblindnesscolorblindness

1 in 10 males1 in 10 males 1 in 100 females1 in 100 females Why do more males Why do more males

have colorblindness?have colorblindness?

14-2 Human Chromosomes14-2 Human Chromosomes HemophiliaHemophilia

• Blood does not clot Blood does not clot properlyproperly

• Is determined by Is determined by two genes on the two genes on the X-chromosomeX-chromosome

• 1 in 10,000 males1 in 10,000 males• Ryan WhiteRyan White

14-2 Human Chromosomes14-2 Human Chromosomes Duchenne Duchenne

Muscular Muscular DystrophyDystrophy• Progressive Progressive

weakening and loss weakening and loss of skeletal muscleof skeletal muscle

• 1 in 3,000 males1 in 3,000 males• Caused by a Caused by a

defective gene that defective gene that codes for a protein in codes for a protein in musclesmuscles

14-2 Human Chromosomes14-2 Human Chromosomes X-chromosome X-chromosome

inactivationinactivation Barr bodyBarr body – dense – dense

area in a nucleus area in a nucleus where the inactivated where the inactivated X chromosome is X chromosome is locatedlocated

Each cell controls Each cell controls which X which X chromosome is chromosome is turned offturned off• Calico catCalico cat

14-2 Human Chromosomes14-2 Human ChromosomesChromosomal Chromosomal

DisordersDisorders NondisjunctionNondisjunction – –

error in which error in which homologous homologous chromosomes fail chromosomes fail to separateto separate

14-2 Human Chromosomes14-2 Human Chromosomes Down syndromeDown syndrome

• Caused by trisomy Caused by trisomy or three copies of or three copies of chromosome chromosome 21(Trisomy 21)21(Trisomy 21)

• 1 in 800 babies1 in 800 babies• This is a This is a

nondisjunction nondisjunction conditioncondition

14-2 Human Chromosomes14-2 Human Chromosomes Sex chromosome Sex chromosome

disordersdisorders Turner’s syndromeTurner’s syndrome

• Females (45,X)Females (45,X)• Sterile Sterile • No sex organsNo sex organs

Klinefelter’s Klinefelter’s syndromesyndrome• Males (47, XXY)Males (47, XXY)• SterileSterile

14-3 Human Molecular 14-3 Human Molecular GeneticsGenetics

Human DNA Human DNA analysisanalysis Search the human Search the human

genome using genome using sequences of DNA sequences of DNA basesbases

14-3 Human Molecular 14-3 Human Molecular GeneticsGenetics

Testing for allelesTesting for alleles• Use labeled DNA Use labeled DNA

probesprobes• Search for changes in Search for changes in

restriction enzymesrestriction enzymes• Test lengths of DNA Test lengths of DNA

strandsstrands

14-3 Human Molecular 14-3 Human Molecular GeneticsGenetics

DNA DNA fingerprintingfingerprinting• No two No two

humans are humans are exactly alikeexactly alike

• Analyze and Analyze and compare low compare low function DNA function DNA segments segments

14-3 Human Molecular 14-3 Human Molecular GeneticsGenetics

The Human The Human Genome ProjectGenome Project An ongoing effort An ongoing effort

to analyze the to analyze the human sequencehuman sequence

Finished in 2000Finished in 2000

14-3 Human Molecular 14-3 Human Molecular GeneticsGenetics

Rapid Rapid sequencingsequencing• Identify separated Identify separated

regions of DNAregions of DNA• Use these areas Use these areas

as markersas markers• Shotgun Shotgun

sequencingsequencing

14-3 Human Molecular 14-3 Human Molecular GeneticsGenetics

Searching for Searching for genes genes • Find DNA Find DNA

sequences sequences known to be known to be promoterspromoters

This is the This is the start of a start of a genegene

14-3 Human Molecular 14-3 Human Molecular GeneticsGenetics

A breakthrough for A breakthrough for everyoneeveryone• Public access to Public access to

Human genome Human genome projectproject

14-3 Human Molecular 14-3 Human Molecular GeneticsGenetics

Gene therapyGene therapy Changing the Changing the

gene that causes gene that causes a genetic disordera genetic disorder• Use viruses to Use viruses to

infect cells with infect cells with good genegood gene

• 1999 - First 1999 - First person cured of person cured of genetic disordergenetic disorder

14-3 Human Molecular 14-3 Human Molecular GeneticsGenetics

Ethical issues Ethical issues in human in human geneticsgenetics

Should we use Should we use genetics to genetics to make people make people better?better?