Two factors contributed to the success of the pteridophytes: the extreme miniaturization of the gametophytic generation and an important development of the sporophytic generation (development of the tree forms).
Pteridophytes are a group of plants that peaked in the Carboniferous (-300 million years). It is the first great terrestrial plant civilization. These plants would have appeared in the Devonian -400 million years ago, perhaps from certain primitive terrestrial plants which, unlike bryophytes, would have favored the diploid generation on the haploid generation.
Particularly well adapted to terrestrial life, they have created, thanks to the development of tree forms, immense forests whose fossilization is at the origin of coal deposits.
Pteridophytes are at the origin of an evolutionary lineage based on the extreme miniaturization of gametophytic generation and an important development of sporophytic generation, leading to all tracheophytes including current flowering plants. Pteridophytes are well adapted to terrestrial life, however fertilization still requires the presence of water since male gametes are swimmers.
Gene regulation is the control of when and where proteins are made.
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Answer:
a) There are lots of genes on chromosome 1 could be affected, and the gametes could be imbalanced (missing segments of DNA or whole chromosomes)
b) Roughly 50%
c) No. I would advise that the couple undergo preimplantation genetic diagnosis, so that a zygote carrying the normal copy of chromosome 1 could be selected.
Explanation:
Chromosome 1 is one of the largest and most gene rich chromosomes. An inversion that covers 70% of its length would cover lots of genes.
While an inversion on its own would not seem problematic (as all the genes on the chromosome are still there), when it comes to meiosis, the sister chromatids would not be able to correctly align, and crossing over would further complicate this. It could also lead to unbalanced gametes missing entire parts of the chromosome. Therefore, there are likely numerous genes that will be affected and messed up by the inversion.
This could explain the high incidence of past still births, as if lots of genes are affected, and non-functional, the pregnancy would be rendered non-viable, or highly deleterious causing premature death.
b) There is a 50% chance of a child inheriting the defective copy of chromosome 1 (and 50% of a chance of them inheriting the normal chromosome 1. Therefore, there is likely a 50% chance that future offspring would be affected by defects
c) No. I would advise that the couple undergo preimplantation genetic diagnosis. In this, the couple undergoes in vitro fertilization (IVF). When embryos are produced through IVF, they can then be tested for the presence of the abnormal chromosome. Embryos will only be implanted into the mother if the normal chromosome 1 is present.
