response to discussion #2 needed in 2 hrs

2. Reply to peer discussion posts: (2 points)

• Discuss one point you like/agree with, and one point you dislike/disagree with and explain why.
• Length of positing consists of approximately 100 words (minimum).

Lus: Achondroplasia is a heterogeneous disorder which causes abnormalities in the development and growth of cartilage and bones. It is a dominant trait that is relatively rare because it is usually caused by a new sporadic gene mutation. Eighty percent of the cases are caused by a new mutation during formation of the egg/sperm cell, or during embryotic development whereas only 20% of cases are passed down by inheritance of the gene. 

A single gene mapped to the short arm of chromosome 4 is responsible for achondroplasia. The mutation causes the protein to be overly active which interferes with skeletal development and growth. It is transmitted as an autosomal dominant trait. Autosomal means the disorder is found in one of the first 22 non-sex chromosomes therefore, can be found in both males and females. Dominant means that it only requires one abnormal gene to be passed down/inherited. It will dominate even though the matching gene from the other parent is normal. 

New mutations are rare because cells have mechanisms in place to prevent or repair them. Most corrections are made during DNA replication otherwise mismatch repair or nucleotide incision repair takes place. This is why achondroplasia is only found in approximately 1 out of 25,000 births; some sources show an average of only 1 out of every 40,000 births. Therefore, although caused by a dominant trait, the mutation occurs very rarely.