Chromosomal Disorders. Non-disjunction During meiosis, chromosomes are supposed to be divided evenly and into gametes. During meiosis, chromosomes are

Chromosomal DisordersChromosomal Disorders

Non-disjunctionNon-disjunction

During meiosis, chromosomes During meiosis, chromosomes are supposed to be divided are supposed to be divided evenly and into gametes.evenly and into gametes.

Sometimes, however, they do Sometimes, however, they do not separate properly. not separate properly. This is called non-disjunctionThis is called non-disjunction

Non-disjunction can lead to Non-disjunction can lead to an extra chromosome or a an extra chromosome or a missing chromosome in the missing chromosome in the

gamete. gamete.

Karyotype*Karyotype*

A picture of an individual’s chromosomesA picture of an individual’s chromosomes Used to determine if the individual has Used to determine if the individual has

the appropriate number of the appropriate number of chromosomes.chromosomes.

In normal humans:In normal humans: 46 chromosomes or 23 pairs of 46 chromosomes or 23 pairs of

chromosomeschromosomes Any change in this number causes Any change in this number causes

abnormality in the individual.abnormality in the individual.

Male or female? Normal?Male or female? Normal?



Down SyndromeDown Syndromeaka Trisomy 21aka Trisomy 21

Three copies of chromosome Three copies of chromosome 21 21

Symptoms: Mental Symptoms: Mental retardation, stunted growth, retardation, stunted growth, altered facial characteristicsaltered facial characteristics

Frequency: 1 out of 800 Frequency: 1 out of 800 birthsbirths


Turner’s SyndromeTurner’s Syndromeaka Monosomy Xaka Monosomy X

Only one sex chromosome (X)Only one sex chromosome (X) Symptoms: Shortness, broad Symptoms: Shortness, broad

chest, infertile, never goes chest, infertile, never goes through puberty, amenorrhea through puberty, amenorrhea (no periods), webbed neck(no periods), webbed neck

Frequency: 1 out of 2,500 Frequency: 1 out of 2,500 femalesfemales


Klinefelter’s SyndromeKlinefelter’s Syndrome

Two X chromosomes and a Y (XXY)Two X chromosomes and a Y (XXY) Symptoms: Sterility, possible breast Symptoms: Sterility, possible breast

development, small testiclesdevelopment, small testicles

(some men show no outward (some men show no outward symptoms)symptoms)

Frequency: 1 out of every 500 Frequency: 1 out of every 500 malesmales


XYYXYY

An X and two Y chromosomes An X and two Y chromosomes (XYY)(XYY)

Symptoms: Usually not noticed; Symptoms: Usually not noticed; often causes increase in height, often causes increase in height, may cause learning disabilitiesmay cause learning disabilities

Frequency: 1 out of 1,000 malesFrequency: 1 out of 1,000 males


Triple X SyndromeTriple X Syndromeaka Trisomy Xaka Trisomy X

Three X chromosomes (XXX)Three X chromosomes (XXX) Symptoms: possible infertility, Symptoms: possible infertility,

tall, small head, learning tall, small head, learning disabilities, delayed puberty, big disabilities, delayed puberty, big distance between eyes, possible distance between eyes, possible mental retardationmental retardation

Frequency: 1 out of 1,000 Frequency: 1 out of 1,000 femalesfemales


Edward’s SyndromeEdward’s Syndromeaka Trisomy 18aka Trisomy 18

Three copies of chromosome 18Three copies of chromosome 18 Symptoms: mental retardation, Symptoms: mental retardation,

small lower jaw, protruding chest, small lower jaw, protruding chest, small, abnormally shaped head, small, abnormally shaped head, heart problemsheart problems

Frequency: 1 out of 3,000 birthsFrequency: 1 out of 3,000 births


Patau SyndromePatau Syndromeaka Trisomy 13aka Trisomy 13

Three copies of chromosome 13Three copies of chromosome 13 Symptoms: mental retardation, Symptoms: mental retardation,

deafness, eye abnormalities, deafness, eye abnormalities, cleft lip, cleft palate, small head, cleft lip, cleft palate, small head, eyes close to each other, eyes close to each other, polydactyly (extra fingers)polydactyly (extra fingers)

Frequency: 1 out of 5,000 birthsFrequency: 1 out of 5,000 births

Autosomal DisordersAutosomal Disorders

Found on the “other” Found on the “other” chromosomes (#’s 1-22).chromosomes (#’s 1-22).

Examples:Examples:Albinism, Cystic Fibrosis, Albinism, Cystic Fibrosis, Sickle Cell Anemia, PKU, Sickle Cell Anemia, PKU, and Huntington’s Disease.and Huntington’s Disease.

AlbinismAlbinism

Carried on chromosome Carried on chromosome #11. #11.

Recessive allele: aaRecessive allele: aa Unable to produce Unable to produce

pigmentation in hair & pigmentation in hair & skin.skin.

AlbinismAlbinism

Cystic FibrosisCystic Fibrosis

Found on chromosome #7.Found on chromosome #7. Very common; Fatal.Very common; Fatal. Recessive: cc Recessive: cc Malfunction in cellular Malfunction in cellular

“pumps” causing buildup “pumps” causing buildup of liquid in lungs.of liquid in lungs.

Cystic FibrosisCystic Fibrosis

Tay-Sachs DiseaseTay-Sachs Disease

Recessive allele: tt; FatalRecessive allele: tt; Fatal Common in Jewish families.Common in Jewish families. Rapid breakdown of Rapid breakdown of

nervous system.nervous system.

Sickle Cell AnemiaSickle Cell Anemia

Recessive: ssRecessive: ss Blood disorder.Blood disorder. Connection with malaria. Connection with malaria.

Common in people whose Common in people whose ancestry traces back to ancestry traces back to Africa.Africa.

Sickle Cell AnemiaSickle Cell Anemia

PKUPKU

Recessive: pp.Recessive: pp. Causes severe mental Causes severe mental

retardation. retardation. No phenylketonuria diet. No phenylketonuria diet.

Huntington DiseaseHuntington Disease

Carried on Dominant Carried on Dominant allele: #4, HH or Hh allele: #4, HH or Hh

No symptoms until later in life No symptoms until later in life - passed down to children. - passed down to children.

Lose control of muscles.Lose control of muscles. Nervous system breaks down.Nervous system breaks down.

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Chromosomal Disorders. Non-disjunction During meiosis, chromosomes are supposed to be divided evenly and into gametes. During meiosis, chromosomes are