What is the genotype of individual III-1? Cannot be determined. Bb bb BB Either

Question

What is the genotype of individual III-1?

Cannot be determined.

Bb

bb

BB

Either BB or Bb

What is the most probable genotype of the originating parents in generation I?

BB x bb

Cannot be determined.

Bb x BB

Bb x Bb

BB x BB

bb x bb

Can it be determined with a high degree of certainly the genotype of the wild type offspring III-3, III-4, and III-5?

Yes, they are all BB

Yes, they are all Bb

No, they can either be BB or Bb.

No, they can either be Bb or bb.

Yes, they are all bb

Explanation / Answer

Genetic defects refer to deformities that exist at birth. They occur sporadically and rarely contribute to major losses of lambs in flocks. There are more than 30 known or suspected genetic defects of sheep. Many are lethal. Others are semi lethal, because the effect is crippling but death is not inevitable, although a proportion do die. Some common genetic defects are entropion (inverted eyelids), cleft palate, parrot mouth (undershot jaw, cryptorchidism (one or both testicles retained in the abdomen), hernias, abdominal impaction, and spider lambs, and even prolapses.

Causes of Genetic Defects

Chromosomes inherited from parents determine an animal's genetic make-up. There are many genes in each chromosome. Genetic abnormalities occur when genes are missing, in excess, mutated or in the wrong location (translocation). A few genes can directly cause an abnormality, however, these are rare. Usually, these genes are recessive, meaning two must be present to cause an abnormality. Both parents must be carriers of the gene for a calf to be abnormal. In this case, only one of every four offspring will be abnormal. Two will be carriers and one will be normal.

Certain conditions show that an abnormality is likely to have a genetic origin:

Below are some of the most common genetic defects in sheep.

Jaw defects Jaw defects are present in almost all breeds of sheep and are associated with failure of the incisor teeth to properly meet the dental pad. A jaw is undershot if the incisor teeth extend forward past the dental pad; it is overshot if the teeth hit in back of the dental pad (this condition is known as parrot mouth). Cull sheep with either of these genetic defects. If the sire and dam can be identified, remove them from the flock.

Overbite: (overshot, parrot mouth, class, overjet, mandibular branchygnathism)
In this condition the upper jaw is longer than the lower jaw. There is a gap between the upper and lower incisors when the mouth is closed. Some lambs that are born with an overbite might self-correct if the bite is no larger than the head of a wooden match. In most breeds of sheep the bites are "set" by the time a lamb is a few months old. An overshot bite will rarely improve after the lamb reaches maturity.

Underbite: (undershot, reverse scissors bite, prognathism)
In this condition the lower jaw is longer than the upper jaw. If the upper and lower jaw meets each other edge to edge, the bite is referred to as an even or level bite. If your lamb has either an overbite or an underbite

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