chromosomes! (lesson)

Each 'normal' egg has 1 X chromosome. Each 'normal' sperm has either 1 X or Y chromosome.


If XO

• When the centromere (a fibre in the centre of the chromosome that helps to split it evenly) splits the chromosome unevenly and 'pulls' an extra X chromosome to one side, there will be 2 X chromosomes in one egg and 0 X chromosomes in the other.
• 0 X chromosome from the mum and 1 X chromosome from the dad.
• The baby will have TURNER'S SYNDROME.

If XXY

• Same scenario as 'XO'. 2 X chromosomes from the mum and 1 Y chromosome from the dad.
• The baby will have KILNELFER'S SYNDROME 
• Physically abnormal: both genitalia present!

If YO

• Same scenario as 'XO' and 'XXY'. 0 X chromosome from the mum and 1 Y chromosome from the dad.
• The baby will not survive. Humans need at least 1 X chromosome to survive!
• Miscarriage!

If XXX

• Same scenario as 'XO', 'XXY' and 'YO'. 2 X chromosomes from the mum and 1 X chromosome from the dad.
• Super female! ONLY 1 X chromosome will be expressed. 
• Physically normal
• MAY be intellectually deficient
• Infertile

If XYY

• Super male! BOTH Y chromosomes are expressed. 
• Physically normal
• MAY be more violent
• Infertile

WHY older women has a higher chance of having an 'abnormal' karyotype offspring: as she gets older, the fiber that pulls the centromere weakens & detoriates. 

*Miscarriages sometimes happen because of genetic defects mentioned.

Blood types!

(Blood type: Chromosome present from each parent)

O: OO

A: AO/AA

B: BO/BB

AB: AB

*Blood types come with Rh+ or Rh-. Interesting fact: women with Rh- cannot produce offspring with men with Rh+, as the baby will be producing antigens against the mother (which will lead to miscarriage).