Achondroplasia is an autosomal dominant form of dwarfism. people with achondroplasia are heterozygotes because carrying two copies of the dominant, mutant allele is fatal during embryogenesis. two people with achondroplasia decide to start a family.

Two people with achondroplasia will have 50% of chance to have a child with achondroplasia. According to Mendelian inheritance, we can indicate dominant allele by A and recessive allele by a, so dominant homozygotes are AA, recessive homozygotes aa and heterozygotes Aa.

Two heterozygotes Aa will have 50% of chances to have a child with achondroplasia (AA), 25% of chances to have a recessive homozygote child (aa) and 25% of chance to concieve a child with two dominant mutant allele (AA):
Parental generation: Aa x Aa
F1 generation: AA, Aa, Aa, aa
Ratio:                1  :     2    :  1

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.