1. Karyotypes & Genetic Disorders

2. Karyotypes
an organized profile of a person’s homologous chromosomes (somatic cells only)
Each pair is organized by size, banding patterns, and location of centromere
Centromere

3. Banding Pattern “Bands” are large segments of DNA
**Remember what chromosomes are made up of

4. Chromosome Pair #23 determines sex Only pair that might NOT match up…
Exception: Position 23
Chromosome Pair #23 determines sex
Only pair that might NOT match up…
WHY?
vs.

5. Female 23rd pair of chromosomes are homologous
Both chromosomes are “X” chromosomes

6. Male 23rd pair of chromosomes are NOT homologous
One chromosome is “X” and the other is a “Y” chromosome

7. Has 46 chromosomes for humans
Normal Karyotypes
Has 46 chromosomes for humans
Arranged in 23 pairs

8. Normal Karyotype
Taken after DNA replication

9. Disjunction
Normal separation of Chromosomes and Chromatids during Meiosis I and Meiosis II (Anaphase I & II)

10. Failure to separate homologous pairs
NON-disjunction
Nondisjunction during Meiosis I
Metaphase I
Anaphase I
Failure to separate homologous pairs

11. Failure to separate Chromatids
NON-disjunction
Nondisjunction during Meiosis II
Metaphase II
Failure to separate Chromatids
Anaphase II

12. What does nondisjunction cause?
Missing Chromosomes – Monomy
Embryo/Fetus will not survive
Means 45 chromosomes
Exception is this can occur on 23rd chromosome pair
Turner’s Syndrome (X-)
Extra Chromosomes – Trisomy
Means 47 chromosomes
Down Syndrome (Trisomy 21)
Patau Syndrome (Trisomy 13)
Klinefelter’s Syndrome (XXY)
XYY Syndrome
And many more………….

13. Trisomy 21 – Down Syndrome
Extra Chromosome 21

14. Trisomy 13 – Patau Syndrome
Extra 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

15. Klinefelter’s Syndrome (XXY)
Extra Sex Chromosome “X”

16. Turner’s Syndrome (X-)

17. 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

18. Jamie Lee Curtis XY male with Androgen Insensitivity Syndrome (AIS)
resistant to androgens
the hormones responsible for male sexual development

19. QUESTIONS???