1. Karyotypes and Nondisjunction

2. KARYOTYPE: Definition
Picture of chromosomes taken during metaphase (mitosis) when chromosomes are fully condensed
Chromosomes are arranged large to small by homologous pairs
sex chromosomes shown last
Normal human karyotypes show 46 chromosomes
44 autosomes (22 pairs of homologous chromosomes)
2 sex chromosomes

3. KARYOTYPE: Human Chromosomes

4. KARYOTYPE: How it is useful
In order to study differences in size, shape, and chromosome number (too few or too many)
Determines the sex of the child
Usually done for humans when a known chromosomal disorder runs in family
(i.e. Down Syndrome)
Can be done for any organism

5. NONDISJUNCTION: Definition and Results
Form of chromosomal mutation during meiosis when homologous chromosomes fail to separate
Results in abnormal number of chromosomes in gametes, which can possibly lead to a disorder in the offspring

6. NONDISJUNCTION: Examples of Disorders
Down Syndrome – (autosome) - three copies of chromosome 21
Karyotype shows 47 chromosomes (Trisomy 21)
Results in various degrees of mental disabilities, causes decrease immunities to diseases/organ defects, distinguished facial features
Edward’s Syndrome – (autosome) three copies of chromosome 18
Karyotype shows 47 chromosomes (Trisomy 18)
Results in failure of all organ systems, death after a few months

7. NONDISJUNCTION: Examples of Disorders
Turner’s Syndrome – (sex chromosome) – only one X chromosome is inherited
Karyotype 45, X
Results in sterile female, short in stature, heart and kidney defects
“Superfemale” – (sex chromosome) – extra X chromosome is inherited
Karyotype 47, XXX (Trisomy X)
Results in healthy, fertile female

8. NONDISJUNCTION: Examples of Disorders
Klinefelter’s Syndrome – (sex chromosome) –extra X chromosome(s) is/are inherited
Karyotype 47, XXY (or even 48, XXXY; 49, XXXXY)
Usually results in sterile male
“Supermale” – (sex chromosome) – extra Y chromosome is inherited
Karyotype 47, XYY
Usually results in sterile, more violent, decreased intelligence, taller male