Human Medical Genetics LECTURE 1 Human Chromosomes Human Karyotype.
The Human Genome Karyotype Mapped out picture of chromosomes arranged in their homologous pairs. ...
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![Page 1: The Human Genome Karyotype Mapped out picture of chromosomes arranged in their homologous pairs. 46 chromosomes in human genome 23 pairs on karyotype.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649e585503460f94b51591/html5/thumbnails/1.jpg)
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
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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
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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?
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Human PedigreesHuman Pedigrees
Female
Male
Partner
Brothers and Sisters
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![Page 6: The Human Genome Karyotype Mapped out picture of chromosomes arranged in their homologous pairs. 46 chromosomes in human genome 23 pairs on karyotype.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649e585503460f94b51591/html5/thumbnails/6.jpg)
![Page 7: The Human Genome Karyotype Mapped out picture of chromosomes arranged in their homologous pairs. 46 chromosomes in human genome 23 pairs on karyotype.](https://reader036.fdocuments.us/reader036/viewer/2022062516/56649e585503460f94b51591/html5/thumbnails/7.jpg)
Genetic Disorders Genetic Disorders from from single Gene single Gene DefectsDefectsDominant/RecessiveDominant/Recessive
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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)
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Albinism
Tay Sachs
Cystic Fibrosis
PKU
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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
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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)
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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.
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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
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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?
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Father(normal vision)
ColorblindNormal vision
Mother (carrier)
Daughter(normal vision)
Son(normal vision)
Daughter(carrier)
Son(colorblind)
Male
Female
Figure 14-13 Colorblindness
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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
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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
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Genetic Disorders from Genetic Disorders from Chromosomal DefectsChromosomal Defects
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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
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