The Human GenomeThe Human GenomeKaryotypeKaryotype

Mapped out picture of chromosomes Mapped out picture of chromosomes arranged in their homologous pairs.arranged in their homologous pairs.

46 chromosomes in human genome46 chromosomes in human genome23 23 pairs on karyotypepairs on karyotype

2 Types of Chromosomes2 Types of Chromosomes

Sex ChromosomesSex Chromosomes Determine individual’s Determine individual’s

gender/sexgender/sex 2 out of 46 (1 pair)2 out of 46 (1 pair) 2323rdrd pair is always sex pair is always sex

pair pair Females: XX (2 X Females: XX (2 X

chromosomes)chromosomes) Males: XY (1 X and 1 Y Males: XY (1 X and 1 Y

chromosome)chromosome)

AutosomesAutosomes Non-sex Non-sex

chromosomeschromosomes Remaining 44 of 46 Remaining 44 of 46

(22 pairs)(22 pairs) Pairs numbered 1 Pairs numbered 1

through 22through 22

Determining gender…Determining gender… Egg CellsEgg Cells-carry -carry

single X single X chromosomechromosome

Sperm CellsSperm Cells-half -half carry single X carry single X chromosome, half chromosome, half carry single Y carry single Y chromosomechromosome

Who determines Who determines gender??? Mom or gender??? Mom or Dad?Dad?

Human PedigreesHuman Pedigrees

Female

Male

Partner

Brothers and Sisters

Genetic Disorders Genetic Disorders from from single Gene single Gene DefectsDefectsDominant/RecessiveDominant/Recessive

Autosomal Recessive Autosomal Recessive DisordersDisorders AlbinismAlbinism-lack of pigment in skin, hair, -lack of pigment in skin, hair,

eyeseyes Cystic FibrosisCystic Fibrosis-excess mucus in lungs, -excess mucus in lungs,

digestive tract, liver (death in childhood)digestive tract, liver (death in childhood) Phenylketonuria (PKU)Phenylketonuria (PKU)-phenylalanine -phenylalanine

buildup in tissues, lack of pigment, mental buildup in tissues, lack of pigment, mental retardationretardation

Tay-SachsTay-Sachs-lipid buildup in brain, mental -lipid buildup in brain, mental deficiency and blindness (death in deficiency and blindness (death in childhood)childhood)

Albinism

Tay Sachs

Cystic Fibrosis

PKU

Autosomal Dominant Autosomal Dominant DisordersDisorders

AchondroplasiaAchondroplasia-dwarfism-dwarfism Huntington’s DiseaseHuntington’s Disease-mental -mental

deterioration and uncontrolled deterioration and uncontrolled movements (appears middle age)movements (appears middle age)

HypercholesterolemiaHypercholesterolemia-excess -excess cholesterol in blood, leads to heart cholesterol in blood, leads to heart diseasedisease

PolydactylismPolydactylism-more than 5 digits-more than 5 digits

Autosomal Codominant Autosomal Codominant DisordersDisorders

Sickle Cell DiseaseSickle Cell Disease-sickle shaped red -sickle shaped red blood cells, damage tissues, oxygen blood cells, damage tissues, oxygen deficit, cause fatigue, more prone to deficit, cause fatigue, more prone to infections (malaria resistance) infections (malaria resistance)

Sex-Linked GenesSex-Linked Genes

Genes located on the X or the Y sex Genes located on the X or the Y sex chromosomeschromosomes

Some X-Linked: MD, melanoma, Some X-Linked: MD, melanoma, colorblindness, hemophiliacolorblindness, hemophilia

Some Y-Linked: testis determining factorSome Y-Linked: testis determining factor Males only have 1 X chromosomeMales only have 1 X chromosomewill will

express phenotype for an X-linked gene from 1 express phenotype for an X-linked gene from 1 allele (either dominant or recessive)allele (either dominant or recessive)

Females have 2Females have 2so they can be dominant, so they can be dominant, carriers, or recessive.carriers, or recessive.

X-Linked Recessive X-Linked Recessive DisordersDisorders

Males only need to inherit 1 recessive allele to Males only need to inherit 1 recessive allele to express the disorderexpress the disorder more common in males more common in males

Females need to inherit 2 recessive copies of Females need to inherit 2 recessive copies of gene to express disordergene to express disorder

ColorblindnessColorblindness-inability to distinguish certain -inability to distinguish certain colorscolors

HemophiliaHemophilia-abnormal blood -abnormal blood clottingclottingexcessive external/internal bleedingexcessive external/internal bleeding

Duchenne Muscular DystrophyDuchenne Muscular Dystrophy-progressive -progressive weakening and loss of skeletal muscleweakening and loss of skeletal muscle

Father(normal vision)

ColorblindNormal vision

Mother (carrier)

Daughter(normal vision)

Son(normal vision)

Daughter(carrier)

Son(colorblind)

Male

Female

Figure 14-13 Colorblindness = carried only on the X chromosome (never the Y)

What are the genotypes and phenotypes of the offspring according to gender?

Father(normal vision)

ColorblindNormal vision

Mother (carrier)

Daughter(normal vision)

Son(normal vision)

Daughter(carrier)

Son(colorblind)

Male

Female

Figure 14-13 Colorblindness

Genetic Problem- Sex-Genetic Problem- Sex-LinkedLinked

A woman who is a carrier for hemophilia A woman who is a carrier for hemophilia mates with a man who has hemophilia. mates with a man who has hemophilia.

Identify the genotypic and phenotypic Identify the genotypic and phenotypic ratios ACCORDING TO GENDER for the ratios ACCORDING TO GENDER for the offspringoffspring

NondisjunctionNondisjunction

Homologous chromosomes fail to Homologous chromosomes fail to separate in Anaphase I of Meiosisseparate in Anaphase I of Meiosis

Results in gametes with abnormal Results in gametes with abnormal chromosome numberschromosome numbersdisordersdisorders

Genetic Disorders from Genetic Disorders from Chromosomal DefectsChromosomal Defects

Chromosomal DisordersChromosomal Disorders

Down SyndromeDown Syndrome-Trisomy 21 (3 copies -Trisomy 21 (3 copies of chromosome #21, instead of the of chromosome #21, instead of the normal 2); mild to severe mental normal 2); mild to severe mental retardation, birth defectsretardation, birth defects

Turner’s SyndromeTurner’s Syndrome-female with only 1 -female with only 1 X chromosome (genotype=XO); no sex X chromosome (genotype=XO); no sex organsorganssterilesterile

Klinefelter’s SyndromeKlinefelter’s Syndrome-male with extra -male with extra X chromosome (genotype=XXY); sterile X chromosome (genotype=XXY); sterile