What is the chromosomal abnormality associated with Down syndrome?
a) an extra Y chromosome
b) a broken branch on the Y chromosome
c) three 21 chromosomes instead of two
d) 24 rather than 23 pairs of chromosomes
Question 2
If only one twin has a certain disease, the twin pair is said to be
a) fraternal.
b) penetrant.
c) karyotypic.
d) discordant.