Question

in theory when a nonisjundtion for chromosme 18 occurs during meiosis 1 four gametes can be produced if these gametes are fertilized with unaffected gametes from the second parent what observations would you make concerning the resulting embryos

Answer 1

Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18.

Step-by-step explanation:

Nondisjunction is the failure of two homologous chromosomes to separate fully during meiosis I. It also occurs during the second meiotic division when the sister chromatids fail to fully separate in meiosis II.

In humans, this condition often result in birth defects or death. One of the conditions is called trisomy 18 where there are is an extra copy of the 18th chromosomes. It does not always lead to death, deformations or disabilities but there may be some effects caused by this. It does not render a human less functional or less viable.

In this scenario, if nondisjunction occurs there will be failure to separate during the meiosis I and II. This cause an uneven segregation of chromosomes and where at least 2 of the gametes will not have the 18th chromosome and the other will have more than one.

Fertilization from an unaffected parent will not restore the number or will increase the number. This will result in very obvious physical and genetic defects.