Maternal Effect

in this video, we're going to briefly introduce maternal effect genes. And so the maternal effect is actually a non Mandali in pattern of inheritance that does not follow the simple Mandali in pattern of inheritance that we've talked about before in some of our previous lesson videos. And so this maternal effect will actually occur when the offspring's phenotype is actually not determined by the offspring's genotype. Instead, the offspring's phenotype is going to be determined by the mother's genotype. And so in other words, what we can say is that in this maternal effect the mother's genotype will dictate the offspring's phenotype regardless of what the offspring's genotype actually is. Now I know this might sound a little strange but the maternal effect does take place in many organisms and in some organisms it takes place fairly often. Now what can be really helpful to help us better understand this maternal effect is if we reflect back on how my aosis occurs. And so if we were to take a look at a cell that is hetero ziggy's for a particular gene, meaning that it would have a dominant allele and a recessive allele, say, a capital D and a lowercase D. Uh well, we know that before this cell undergoes mitosis it would undergo DNA replication to replicate each of these alleles. And so after DNA replication, which we can write in DNA replication here, we know that each of these alleles is going to be replicated. And so we would end up with a single cell that is going to have identical replicates of each of these alleles. And so now that the cell has replicated its DNA, it's ready to begin May aosis. And we know from our previous lesson videos that may aosis consists of two rounds of cell division mitosis one and mitosis too. And so what you'll notice here is that my aosis one, which would be this first round of cell division will separate or segregate these alleles. It will separate the dominant alleles from the recessive alleles. And so over here we would have the two dominant alleles. And over here we would have the two recessive alleles. And again this arrow here represents mitosis one. Uh And so what's really important to note is that although the dominant alleles are on this left cell and the recessive alleles are on the right cell, it's still possible for each of these cells to have some leftover gene products found in each other. And so what I mean by that is that some gene products of the dominant allele may still be found in this cell over here. Uh And some gene products of the recessive allele may still be found in the left cell over here. And so that is something important to keep in mind because let's say for example uh some leftover gene product of this dominant allele is found in this cell, which we can just represent with a red dot. Well as my aosis continues again mitosis two would happen next where each of these cells would continue to divide and we would get these hap Lloyd sells at the end ah like as we see here. Mhm. Um The leftover gene products would also still be in here. And the leftover gene products in some cases can end up influencing the offspring's phenotype. And so this is exactly what happens with this maternal effect. And that's exactly what we're trying to explain here with this second bullet of text that we have right here. And so basically what this is saying is that the maternal effect can occur when the mother's egg ends up containing some leftover gene products. Either some leftover M. RNA or some leftover proteins. And again those leftover gene products and our example are represented by this little red dot over here and again, those leftover gene products can end up influencing the offspring's phenotype. And so this is how the mother's genotype ends up influencing the offspring's phenotype. Now, a classic example of the maternal effect is actually the shell coiling of the snail Leonia. And so this snail Lynell can either form right handed coils or it can form left handed coils. Now the right handed coils are associated with the dominant allele. And so a hetero, I'm sorry homos I guess dominant genotype or a hetero zigo's genotype would form right handed coils. Whereas a homo zegas recessive genotype would end up forming left handed coils. And so you might expect with simple Mandali in inheritance that homo zika's recessive offspring would form left handed coils. However, because the coiling is an example of the maternal effect, it turns out that a Homo zegas recessive offspring will actually not form left handed coils, like what you might expect. Instead, the offsprings phenotype is only going to be dictated by the mother's genotype. And so even though the offspring has a home Ozekis recessive genotype, that would you might expect would form left handed coils. It turns out that if the mother is Homo zegas dominant or hetero sickness, then this offspring is going to form right handed coils. And this is exactly what we mean by the maternal effect that the offspring's phenotype is going to be dictated by the mother's genotype. And so down below notice, we've got this image of this snail's coils and its shell and this is showing you a left handed coil here. Um But again, this here really concludes our brief lesson on maternal effect genes and how the maternal effect is when an offspring's phenotype is dictated by the mother's genotype, and it's not dictated by the offspring's genotype. And so I'll see you all in our next video

Okay, so this question says, what controls the inheritance of an offspring phenotype when the trade is controlled through maternal effect? So if there's a maternal effect trait, what is actually controlling the phenotype? Is it the offspring's genotype, the mother's genotype or the father's genotype? What do you think? So, in maternal effect, the offspring's genotype doesn't matter at all. In fact, it's the mother's genotype that controls the offspring's genotype when it's controlled through maternal effect inheritance. So with that, let's move on.

Okay, so true or false. Maternal inheritance and maternal effects are two terms for the same type of inheritance, so that the same thing, but to just two different names for it, What do you think? Right, So the answer here is false. You are two very different things. Maternal inheritance is when you get something solely from the mother. So for instance, you inherit mitochondria only from the mother and not from the father. Maternal effect is when the genotype of the mother actually controls the phenotype and not the genotype of the organism or the offspring itself. So two completely different things. So with that let's move on.