Birth, twins, new techniques and Chapter 3 in one view
Answers are for parents and teachers.
1
A town has 3 440 births in a year. By the book’s figure of about one twin birth in 86, about how many twin births are expected?
3 440 ÷ 86 = 40 twin births. A real year can differ, because 1 in 86 is an average.
2
Name one thing identical twins and a clone have in common, and one difference in how they begin.
Both have the same genes as another individual. Identical twins begin from one fertilized ovum whose cell mass splits; a clone begins from an egg cell that is given the nucleus of another individual.
3
A plant has 2N = 28. How many chromosomes are in each microspore made by meiosis, and how many in the zygote after fertilization?
28 ÷ 2 = 14 in each microspore. After fertilization 14 + 14 = 28 in the zygote.
4
Why are fraternal twins no more alike than other brothers and sisters?
They come from two different ova fertilized by two different sperm, so they have different genes, as other brothers and sisters do.
5
Gamete banks store gametes of farm animals. Give one reason why this is useful.
The gametes can be used after the donors have died, or to keep rare species.