NondisjunctionHomework 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.

• The zygote that has been created will have an extra or missing chromosome. This would result in an inherited genetic disorder.

oIn most cases, the presence of an additional chromosome or missing chromosome results in the death of the zygote.

Nondisjunction

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

KaryotypesEverything okay here??

What gender??

2 different sized sex chromosomes = male

Down’s syndrome

•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

Everything okay here??

Turner’s syndrome

• 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%)

Everything okay here??

Turner’s syndrome

Kleinfelter’s syndrome

Everything okay here??

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

Kleinfelter’s syndrome

Patau’s syndrome

Everything okay here??

Patau’s Syndrome

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