Nondisjunction Homework for 11/13/14 Fill out notes on the back of page 34, which is the Cell Division Venn Diagram

Nondisjunction Although the events of meiosis usually proceed accurately, sometimes an accident occurs and the chromosomes fail to separate correctly. This is known as nondisjunction.

Nondisjunction The zygote that has been created will have an extra or missing chromosome. This would result in an inherited genetic disorder. In most cases, the presence of an additional chromosome or missing chromosome results in the death of the zygote.

Nondisjunction Monosomy - the presence of only one chromosome from a pair in a cell's nucleus. Trisomy – the presence of three chromosomes instead of 2 in a cell’s nucleus.

Karyotypes When you are born, doctors take a sample of your blood and create a karyotype. This will enable the doctor to see if you have any additional or missing chromosomes. A karyotype is a standardized arrangement of all the chromosomes of a cell.

Karyotypes Homologous chromosomes are paired up, then they are put in order from the LARGEST chromosome pair to the smallest.

Karyotypes 2 x chromosomes = GIRL autosomes sex chromosomes

Karyotypes Everything okay here?? What gender?? 2 different sized sex chromosomes = male

Down’s syndrome Everything okay here?? trisomy 21 trisomy 21 decreased muscle tone at birth asymmetrical or odd-shaped skull round head with flat area at the back of the head slanting eyes small mouth with protruding tongue single crease on the palm slowed growth and development delayed mental and social skills trisomy 21 trisomy 21

Turner’s syndrome Everything okay here?? monosomy X monosomy X short stature (affects almost all girls with Turner, to different degrees) failure of ovaries to develop (90-95% of girls) webbed neck (25%) or short neck (40%) abnormal fingernails and toenails (70%) hearing disorders (50-90%) frequent ear infections in childhood (75%) monosomy X monosomy X monosomy X

Turner’s syndrome XO XO XO XO

Kleinfelter’s syndrome Everything okay here?? Kleinfelter’s syndrome XXY XXY XXY

Kleinfelter’s syndrome No symptoms - some men are unaware they have an extra chromosome Enlarged male breasts - only severe in about 10% of cases Sparse facial hair Sparse body hair Inability to produce sperm Tallness - more likely to be taller than non-XXY males. Thinness Normal intelligence Language impairment Delayed language XXY XXY

Kleinfelter’s syndrome XXY XXY XXY XXY

Patau’s syndrome trisomy 13 trisomy 13 trisomy 13 trisomy 13 Everything okay here?? Patau’s syndrome trisomy 13 trisomy 13 trisomy 13 trisomy 13

Patau’s Syndrome Mental retardation, severe Seizures Small head Scalp defects (absent skin) Small eyes (microphthalmia) Cleft lip and/or palate