Karyotypes and Karyotypes and NondisjunctionNondisjunction

KARYOTYPE: DefinitionKARYOTYPE: Definition Picture of chromosomes taken during Picture of chromosomes taken during

metaphase metaphase (mitosis)(mitosis) when chromosomes are when chromosomes are fully condensedfully condensed

Chromosomes are arranged large to Chromosomes are arranged large to small by homologous pairssmall by homologous pairs– sex chromosomes shown lastsex chromosomes shown last

NormalNormal human karyotypes show 46 human karyotypes show 46 chromosomeschromosomes– 44 autosomes (22 pairs of homologous 44 autosomes (22 pairs of homologous

chromosomes)chromosomes)– 2 sex chromosomes2 sex chromosomes

KARYOTYPE: Human Chromosomes

KARYOTYPE: How it is KARYOTYPE: How it is usefuluseful

In order to study differences in size, In order to study differences in size, shape, and chromosome number shape, and chromosome number (too few or (too few or too many)too many)

Determines the sex of the childDetermines the sex of the child

Usually done for humans when a known Usually done for humans when a known chromosomal disorder runs in family chromosomal disorder runs in family – (i.e. Down Syndrome)(i.e. Down Syndrome)

Can be done for any organismCan be done for any organism

NONDISJUNCTION:NONDISJUNCTION:Definition and ResultsDefinition and Results

Form of chromosomal mutation during Form of chromosomal mutation during meiosis when meiosis when homologous chromosomeshomologous chromosomes fail to separatefail to separate

Results in abnormal number of Results in abnormal number of chromosomes in gametes, which can chromosomes in gametes, which can possibly lead to a disorder in the offspringpossibly lead to a disorder in the offspring

NONDISJUNCTION:NONDISJUNCTION:Examples of DisordersExamples of Disorders

Down SyndromeDown Syndrome – – (autosome)(autosome) - three copies - three copies of chromosome 21of chromosome 21– Karyotype shows 47 chromosomes Karyotype shows 47 chromosomes (Trisomy 21)(Trisomy 21)

– Results in various degrees of mental Results in various degrees of mental disabilities, causes decrease immunities to disabilities, causes decrease immunities to diseases/organ defects, distinguished facial diseases/organ defects, distinguished facial featuresfeatures

Edward’s SyndromeEdward’s Syndrome – – (autosome)(autosome) three three copies of chromosome 18copies of chromosome 18– Karyotype shows 47 chromosomes Karyotype shows 47 chromosomes (Trisomy 18)(Trisomy 18)

– Results in failure of all organ systems, death Results in failure of all organ systems, death after a few monthsafter a few months

NONDISJUNCTION:NONDISJUNCTION:Examples of DisordersExamples of Disorders

Turner’s SyndromeTurner’s Syndrome – – (sex chromosome)(sex chromosome) – only – only one X chromosome is inheritedone X chromosome is inherited– Karyotype 45, XKaryotype 45, X– Results in sterile female, short in stature, Results in sterile female, short in stature,

heart and kidney defectsheart and kidney defects

““Superfemale”Superfemale” – – (sex chromosome)(sex chromosome) – extra X – extra X chromosome is inheritedchromosome is inherited– Karyotype 47, XXX Karyotype 47, XXX (Trisomy X)(Trisomy X)

– Results in healthy, fertile femaleResults in healthy, fertile female

Klinefelter’s SyndromeKlinefelter’s Syndrome – – (sex chromosome)(sex chromosome) – –extra X chromosome(s) is/are inheritedextra X chromosome(s) is/are inherited– Karyotype 47, XXY Karyotype 47, XXY ((or even 48, XXXY; 49, XXXXYor even 48, XXXY; 49, XXXXY))

– Usually results in sterile maleUsually results in sterile male

““Supermale”Supermale” – – (sex chromosome)(sex chromosome) – extra Y – extra Y chromosome is inheritedchromosome is inherited– Karyotype 47, XYYKaryotype 47, XYY– Usually results in sterile, more violent, Usually results in sterile, more violent,

decreased intelligence, taller maledecreased intelligence, taller male

NONDISJUNCTION:NONDISJUNCTION:Examples of DisordersExamples of Disorders