Biology

I thought that it would not be the same as its parents if each parents' genotypes are not the same, because many siblings do not have the same genotype as each other.

Is is true that when a specie inbreeds, the offspring are homozygous? And when it outbreeds, the offspring are heterozygous? Why is this the case?

Is it true for self pollination, that when a plant self pollinates, the resulting offspring all are the same genotype as the parent plant? And heterozygous offspring result when a plant cross pollinates?

Broadly speaking yes, Inbreeding increases homozygosity. This is because in inbreeding, individuals produce offspring with individuals that have similar genotypes and similar alleles, and therefore you have less mixing of different alleles to produce heteozygous offspring.

If a plant selfs to produce offspring, then the offspring will have a subset of the genetic variation in their parent - this is because all of their genetic material comes from one parent. Moreover, the parent may be heterozygous Aa at a specific locus but then give the offspring AA or aa at that same locus, which means that the offspring only has one of the alleles and therefore less genetic variation at that locus than its parent. When you think about all the loci across the plant genome, this is likely to happen at at least a few when the parent plant selfs, meaning that the offspring produced will likely have a subset of the genetic variation of the parent when produced by selfing, and not necessarily the exact same genotype.

Cross-pollination does indeed increase heterozygosity, because it enourages mixing of different alleles across all loci, and so is much more likely to produce heterozygous offspring.

hope that helps

Thanks a lot for the reply, highly appreciate it!

One more question. Suppose there are 2 animals/plants of the same specie. Both breed. And should produce homozygous offspring, because they're the same specie and are a product of inbreeding, not outbreeding.

Now, this is where I'm confused. Let's consider 1 gene for simplicity. Suppose a gene for fur color is denoted by A. It's recessive form is a. Assuming one parent is AA at a locus and the other can be aa at the particular locus, the offspring are Aa. The offspring produced hence won't be homozygous, despite being the same specie and being a consequence of inbreeding! The result suggests the parents outbred, because it is suggested heterozygous organisms are produced as a result of outbreeding, not inbreeding. I'd highly appreciate another reply.


In the past papers, it is suggested in the mark scheme multiple times that homozygous organisms as produced when parents inbreed, heterozygous are produced when parents outbreed.