Karyotypes & Genetic Disorders. Karyotypes an organized profile of a person’s homologous...
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Transcript of Karyotypes & Genetic Disorders. Karyotypes an organized profile of a person’s homologous...
Karyotypes&
Genetic Disorders
Karyotypesan organized profile of a person’s homologous
chromosomes (somatic cells only)
Each pair is organized by size, banding patterns, and location of centromere
Centromere
Banding Pattern“Bands” are large segments of DNA **Remember what chromosomes are made up of
Exception: Position 23Chromosome Pair #23 determines sex
Only pair that might NOT match up…
WHY?
vs.
Female
23rd pair of chromosomes are homologous
Both chromosomes are “X” chromosomes
Male23rd pair of chromosomes are
NOT homologous
One chromosome is “X” and the other is a “Y” chromosome
Normal Karyotypes
Has 46 chromosomes for humansArranged in 23 pairs
Normal Karyotype
• Taken after DNA replication
DisjunctionNormal separation of Chromosomes and Chromatids during Meiosis I and Meiosis II
(Anaphase I & II)
NON-disjunctionNondisjunction during Meiosis I
Metaphase I Anaphase I Failure to separate
homologous pairs
NON-disjunctionNondisjunction during Meiosis II
Metaphase II
Anaphase II
Failure to separate
Chromatids
What does nondisjunction cause?Missing Chromosomes – Monomy
Embryo/Fetus will not surviveMeans 45 chromosomesException is this can occur on 23rd chromosome pair
Turner’s Syndrome (X-)
Extra Chromosomes – TrisomyMeans 47 chromosomes
– Down Syndrome (Trisomy 21)– Patau Syndrome (Trisomy 13)– Klinefelter’s Syndrome (XXY)– XYY Syndrome– And many more………….
Trisomy 21 – Down SyndromeExtra Chromosome 21
Trisomy 13 – Patau SyndromeExtra Chromosome 13
Symptoms can include•Cleft lip or palate •Close-set eyes -- eyes may actually fuse together into one •Decreased muscle tone •Extra fingers or toes•Hernias•Hole, split, or cleft in the iris•Low-set ears •Mental retardation•Scalp defects (absent skin) •Seizures •Single palmar crease •Skeletal (limb) abnormalities •Small eyes •Small head•Small lower jaw •Undescended testicle
Klinefelter’s Syndrome (XXY)Extra Sex Chromosome “X”
Turner’s Syndrome (X-)
XYY Syndrome
• XYY syndrome is characterized by an extra copy of the Y chromosome
• males with this condition may be taller than average
• This chromosomal change typically causes no unusual physical features
• Most males with XYY syndrome have normal sexual development and are able to father children
Jamie Lee Curtis• XY male with Androgen
Insensitivity Syndrome (AIS)
• resistant to androgens– the hormones
responsible for male sexual development
QUESTIONS???