It is thought that<unk>  is caused by an autosomal, recessive allele. To avoid a potential "lethal dose", both parents must submit to genetic testing. If a child is conceived with another carrier the outcome may be lethal, or the child may suffer from<unk>  or dwarfism. This means that even though both parents are completely normal in height, the child will have one of the two types of skeletal dysplasia. Type 1 (short limb dysplasia), the more common of the two, is characterised by a long trunk and extremely shortened extremities. Type 2, short-trunk dysplasia, is characterised by a shortened trunk and normal size extremities. Those affected by<unk>  may also experience metabolic and hormonal disorders, both of which may be monitored and controlled by hormonal injections. Animals have been bred specifically to elicit<unk> c traits for research purposes and to more easily allow animals to free-roam without escaping by, for example, jumping over ranch fences. One example of this is the Ancon sheep, which was first bred from a lamb born in 1791 with naturally occurring<unk> . Inheritance<unk>  has an autosomal recessive pattern of inheritance.<unk>  is an autosomal recessive disorder, meaning that in order for this disease to be expressed, the affected individual must possess two copies of the allele for the disorder. The inheritance of the<unk>  gene is as follows: Let us name the dominant allele for normal stature "T", and the recessive allele coding for<unk>  "t"; either one or the other is going to be chosen during random selection for a particular "seat" on its chromosome. If both parents are heterozygous for<unk> , they each possess one copy of the T allele and one copy of the t allele (each person has two copies of every autosomal allele, a paternal and a maternal one). When they reproduce there are then four possible alleles that may be chosen at random, two of them are the T allele (one from the father, one from the mother), and two are t alleles (again, one from the father, and one from the mother). The resulting Mendelian ratio of offspring from this mating would then be: * 1 homozygous dominant, or TT * 2 heterozygous, or Tt * 1 homozygous recessive, or tt The phenotypes of the offspring would be three unaffected, normal-stature offspring, and one affected<unk> c offspring; there would be a 25% chance of having an affected offspring if both parents were carriers of the recessive allele. Other probabilities for the other possible allele combinations concerning this gene are: 0% chance of affected offspring if only one parent is a carrier, 0% chance of affected offspring if one parent is affected and the other does not carry the allele, and 50% chance of affected offspring if one parent is affected and the other is a carrier. These ratios may be found by drawing up a standard Mendelian punnett square. Percentage risk of inheritance * Both average parents *# A couple already has a child with<unk> ; the risk of inheritance for the next child to have the disorder is 0.1% (less than 1 in 1,000) *# The risk that the normal-statured child will have at least one offspring with this disorder is 0.01% (less than 1 in 10,000) * One parent with<unk>  and one parent without *# One child with normal height; the probability of that child having offspring with<unk>  is 0.01% (less than 1 in 10,000) *# One child with normal stature; the probability of the next having<unk>  is 50% (1 in 2) *# One child with normal stature; the probability of the next not having<unk>  is 50% (1 in 2) * Both parents with<unk>  *# The probability of offspring affected by<unk>  is 100% (4 in 4) *# The probability of offspring to be of normal size is 0% (0 in 4)
Chondrodystrophy
Monomelic amyotrophy
Muscular dystrophy
Congenital muscular dystrophy
Loxoscelism
Arthrogryposis
Cone dystrophy
Congenital myopathy