Answer;
-Inactivation; limited
Differentiation requires inactivation of particular genes to produce populations with limited capabilities that form tissues.
Explanation;
-Cell differentiation is how generic embryonic cells become specialized cells. This occurs through a process called gene expression.
-Gene expression is the specific combination of genes that are turned on or off (expressed or repressed), and this is what dictates how a cell functions.
-Gene expression plays a critical role in the morphological changes that take place in a developing embryo and fetus and in the differentiation of stem cells to form specialized cells.
Because they will grow really long if you don't
The Hardy-Weinberg equation is as follows:


Where:
(convert all % to decimals)
p= homozygous dominant
q= homozygous recessive
pq= heterozygous
While you did not specify whether the 0.2 frequency was for dominant or recessive, we can still figure out the answer.
Using the 1st equation, we can solve for the other dominant/recessive frequency:
1-0.2=0.8
Meaning that:
p= 0.8 & q=0.2
If the heterozygouz frequency is 2pq, then it becomes a simple "plug & chug" sort of approach.
2(0.8)(0.2)= 2(0.16)= 0.32
So, the heterozygous frequency would be:
0.32
Hope this helps!
An asteroid hitting the earth would cause a lot of dust, ash, and other debris to go into the atmosphere which would block the sun which would cause the temperature to decrease.