1. Mistakes in Meiosis

2. Nondisjunction Nondisjunction
The failure of homologous chromosomes to separate properly during meiosis.
What should happen
Nondisjunction

3. The results
If the abnormal gametes is fertilized the results

4. Polyploidy the condition where cells have multiple sets of chromosomes
usually 3-4 sets
Most often found in plants, rare in animals
Polyploidy is the condition where cells have more than one set of chromosomes, as supposed to haploidy. In most organisms which reproduce by sexual reproduction the usual state of cells is diploidy. Some plants (especially flowering plants) exibit triploidy and tetraploidy, or even octoploidy e.g. in strawberry plants and sugar cane.
Plants are more likely than animals to exhibit polyploidy because their gametes are produced from somatic cells rather than germ-line cells, and therefore go through more cell cycles, but polyploidy can also occur in some animals. Polyploidy has been observed in insects, fish, amphibians, reptiles, and once in mammals (a rat), though it was once thought polyploidy would be fatal to mammals.
Polyploidy is a route by which plants could increase their chromosome numbers, and the size of their genome. Over time changes in the duplicated chromosomes are liable to build up until they can be distinguished as different chromosomes, and the organism can once again be described as diploid ('diploidisation', during which the haploid chromosome number of the organism becomes difficult to define). Polyploidy will duplicate the genes on each chromosome, and during the subsequent changes many copies will be 'turned off', increading pseudogenes and the proportion of 'Junk DNA' in the genome.
Polyploid plants are often larger and have other accentuated charactoristics, making them useful in agriculture and horticulture. Polyploidy can be artificially induced in plants by botanists and horticulturalists, e.g. with the chemical colchicine, which provents chromosomes from separating during mitosis.

5. Examples of Polyploidy
Diploid & tetraploid
many plants
Octoploidy
strawberries
Triploid
seedless watermelon
Seedless watermelon is the result of a cross between 4n and 2n – 3n offspring is sterile

6. Trisomy The zygote has an extra chromosome
Organisms with an extra chromosome sometimes survive

7. Examples of trisomy in humans
Trisomy 21: Downs Syndrome
Trisomy 18: Edwards syndrome
Trisomy 13: Patau syndrome
XXY: Klinefelter's syndrome
Trisomy 1: rare
Trisomy 2: associated with loss of pregnancy
Trisomy 3: lethal
Trisomy 4: lethal
Trisomy 5: lethal
Trisomy 6: rare, no heath concerns in know cases (six total cases)
Trisomy 7: never reported in live birth childern
Trisomy 8:
Trisomy 9:
Trisomy 10: lethal
Trisomy 11:
Trisomy 12:majority have normal outcomes
Trisomy 13: Patau syndrome 0.03
Trisomy 14:
Trisomy 15: lethal
Trisomy 16: lethal
Trisomy 17: not reported
Trisomy 18: Edwards syndrome .2%
Trisomy 19:
Trisomy 20: not viable
Trisomy 21: Downs Syndrome
Trisomy 22:
Trisomy 23:
Trisomy x:
XXY: normal development, slightly taller, decreased sperm quality
Trisomy X: super female syndrome

8. Trisomy 21: Downs Syndrome
Decreased muscle tone at birth
Separated sutures (joints between the bones of the skull)
Asymmetrical or odd-shaped skull
Round head with flat area at the back of the head (occiput)
Small skull (microcephaly)
Upward slanting eyes, unusual for ethnic group
Small mouth with protruding tongue (see tongue problems)
Broad short hands
Single crease on the palm
Retarded growth and development
Delayed mental and social skills (mental retardation)
Iris lesion (an abnormality of the colored part of the eye called Brushfield spots)

9. Trisomy 18: Edwards syndrome
Most children die in the first year of life, some have lived 10 years
Growth deficiency
Feeding difficulties
Breathing difficulties
Developmental delays
Mental Retardation
Undescended testicles in males
Prominent back portion of the head
Small head (microcephaly)
Low-set, malformed ears
Abnormally small jaw (micrognathia)
Small mouth
Cleft lip/palate
Upturned nose
Narrow eyelid folds (palpebral fissures)
Widely-spaced eyes (ocular hypertelorism)
Dropping of the upper eyelids (ptosis)
Overlapped, flexed fingers
Underdeveloped or absent thumbs
Underdeveloped nails
Webbing of the second and third toes
Clubfeet
Small pelvis with limited movements of the hips
Short breastbone
Kidney malformations
Structural heart defects at birth (i.e., ventricular septal defect, atrial septal defect, patent ductus arteriosus)

10. Trisomy 13: Patau syndrome
Mental retardation, severe
Seizures
Small head (microcephaly)
Scalp defects (absent skin)
Small eyes (microphthalmia)
Cleft lip and/or palate
Eyes close set (hypotelorism) -- eyes may actually fuse together into one
Iris defects (coloboma)
Pinna abnormalities and low set ears
Simian crease
Extra digits (polydactyly)
Hernias: umbilical hernia, inguinal hernia
Undescended testicle (cryptorchidism)
Hypotonia
Micrognathia
Skeletal (limb) abnormalities

11. XXY: Klinefelter's syndrome
Klinefelter Syndrome is probably the most common chromosomal variation found in humans. In random surveys, it is found to appear about once in every 500 to one in every 1,000 live born males.
sterility, breast development, incomplete masculine body build, and social and/or school learning problems

12. Monosomy The zygote is lacking a chromosome
Organisms lacking one or more chromosomes rarely survive

13. Examples of monosomy in humans
Monosomy X: Turners Syndrome

14. Monosomy X: Turners Syndrome
Short height
Webbed neck
Drooping eyelids
A "shield-shaped", broad, flat chest
Absent or incomplete development at puberty, including sparse pubic hair and small breasts
Infertility
Dry eyes
Absent menstruation
Absent normal moisture in vagina; painful intercourse

15. Karyotyping
a picture showing the number and type chromosomes in a cell
Chromosomes are arranged in order from largest to smallest
Shows major chromosomal abnormalities
i.e. pieces of chromosomes are missing of extra copies (will not show defective gene)

16. Human Karyotype