Q 01/05

Which fruit, sold mostly as the Cavendish variety, is seedless because its three chromosome sets jam meiosis?

A) Pineapple

B) Clementine

C) Banana

D) Navel orange

Answer · why

C) Banana

Banana plants sold in shops carry every chromosome in triplicate, so some are left without a partner and seeds almost never form. Growers have to clon...

Q 02/05

Which hybrid animal is usually sterile because its 63 chromosomes cannot form matching pairs in meiosis?

A) Mule

B) Liger

C) Beefalo

D) Wolfdog

Answer · why

A) Mule

Mule cells hold 32 chromosomes from a horse mother and 31 from a donkey father, so one is always left over. A few female mules have still managed to p...

Q 03/05

Human egg cells begin meiosis at which point in a woman's life, then pause partway for years or decades?

A) At puberty

B) Before birth

C) In infancy

D) At each ovulation

Answer · why

B) Before birth

Before birth is the surprising answer: every egg a woman will ever release started dividing while she was still a fetus. Each one resumes only around ...

Q 04/05

Which condition, the commonest human chromosome disorder, arises when meiosis fails to split a chromosome 21 pair?

A) Cystic fibrosis

B) Hemophilia

C) Tay-Sachs disease

D) Down syndrome

Answer · why

D) Down syndrome

Down syndrome affects about 1 in 1,000 babies worldwide. In nearly nine cases in ten, the extra chromosome arrives in the egg rather than the sperm.

Q 05/05

Which fact about a mother most sharply raises the odds that meiosis mis-sorts the chromosomes in her eggs?

A) Her diet

B) Her blood type

C) Her age

D) Her height

Answer · why

C) Her age

Her age matters because eggs sit paused in mid-division for decades, and the ties holding their chromosomes together slowly weaken. Sperm, by contrast...