A seed geneticist discovers the endosperm has two maternal and one paternal genome. Which process led to this genetic ratio?
Select an option:
- Syngamy failure
- Self-fertilization
- Triple fusion during double fertilisation
- Haploid fusion
Answer (2)
The genetic ratio of two maternal and one paternal genome in the endosperm is a result of triple fusion during double fertilization in angiosperms. This process involves one sperm fertilizing the egg and another sperm fusing with two polar nuclei to form the endosperm. Thus, the correct answer is that triple fusion during double fertilization is the process that leads to this genetic ratio.
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The genetic ratio of two maternal genomes and one paternal genome found in the endosperm is the result of 'Triple fusion during double fertilization,' which is a unique process that occurs in the reproduction of flowering plants.
To understand how this genetic composition arises, it's important to look at the process of double fertilization in plants:
Pollination and Pollen Tube Growth : When a pollen grain lands on the stigma of a flower, it germinates and grows a pollen tube down into the ovary to reach the ovule.
Double Fertilization : Inside the ovule, there are two male gametes released from the pollen tube:
One sperm cell fuses with the egg cell to form a diploid zygote (this leads to the formation of the embryo).
The second sperm cell fuses with the two haploid polar nuclei found in the central cell of the ovule, resulting in a triploid cell. This process is known as 'triple fusion.'
Endosperm Formation : The triploid cell develops into the endosperm, which is the tissue that provides nourishment to the developing embryo. This triploid nucleus contains two sets of chromosomes from the mother (due to the fusion with two polar nuclei) and one set from the father (from the second sperm cell).
The endosperm is thus genetically 2n maternal and 1n paternal, explaining why the endosperm has two maternal genomes and one paternal genome. This unique process helps ensure that the embryo has a ready supply of nutrients for its development inside the seed.
Therefore, the correct option in the multiple-choice question is: 'Triple fusion during double fertilization.'
