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What term defines chance changes in alelle frequency that have a big effect in small populations?
The term that defines chance changes in allele frequency that have a significant effect in small populations is "genetic drift." Genetic drift occurs when random events cause certain alleles to become more or less common in a population, which can lead to reduced genetic variation. This phenomenon is particularly pronounced in small populations, where random fluctuations can have a larger impact on overall genetic diversity.
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What circumstances that genetic drift occur?
Genetic drift is the fluctuation of allele frequencies in a population due to chance. Chance plays a role in several ways. Copies of alleles can be lost because they never make it into gametes. Another possibility is, if the allele copy makes into a sperm, that sperm isn't the one that fertilizes an egg. Maybe the organism that carries copies of the allele in its gametes fails to find a mate, or is killed before reproducing. These kinds of events can influence the frequency of that alelle in a population, and occurs regardless of any selection for or against that allele. Obviously, the smaller the population, the larger the effect drift has on the allele frequency. For example, consider a population of four organisms. Each has two copies of a particular gene (one on each chromosome). Now, consider a mutation that creates a new allele for that gene, and that it appears on one chromosome of one individual. That allele will have a frequency of 1/8 in that population, so if it is lost, the frequency change will be 1/8. Now imagine a population of eight individuals; the frequency of the new allele would be 1/16, so if it was lost, the change in frequency would be less than in a population of four. It should therefore be easy to see that the effect of genetic drift on allelic frequency change is dramatically less in very large populations. In fact, in an essentially infinite population, genetic drift would have a negligible effect on the frequency of an allele. Another factor that can influence allele frequency, and which is a part of genetic drift is non-random mating. If an organism does not have an equal probability of mating with any other organism in a population, then some alleles will increase or decrease in frequency simply due to that. For instance, if a population exists over a large geographic range, individuals that live closer to each other have a greater probability of mating than those who live far apart. Species who employ reproductive strategies such as leks,where males gather together and compete for the privilege of mating with females are also examples of non-random mating. Lekking increases the effects of drift because it reduces what biologists call the effective population size, or the number of breeding adults. For the above reasons, when population geneticists want to study factors that affect the frequency of an allele (such as natural selection), and they want to minimize the effects of drift, they model populations that are very large (essentially infinite) and assume random mating.
What are two processes through which genetic drift can occur?
Random events in small populations and the founder effect. The first can be just about any thing, but the second is about the emigration of a part of a population to another area/population. These emigrants are not fully representative of the parent populations allele frequency; hence drift.Other causes of genetic drift:1- Changes in allele frequency: Sometimes, there can be random fluctuations in the numbers of alleles in a population. These changes in relative allele frequency, called genetic drift, can either increase or decrease by chance over time.Typically, genetic drift occurs in small populations, where infrequently-occurring alleles face a greater chance of being lost.2- population bottleneck : Genetic drift is common after a population experiences a population bottleneck. A population bottleneck arises when a significant number of individuals in a population die or are otherwise prevented from breeding, resulting in a drastic decrease in the size of the population.3-Distribution: How does the physical distribution of individuals affect a population? A species with a broad distribution rarely has the same genetic makeup over its entire range. For example, individuals in a population living at one end of the range may live at a higher altitude and encounter different climatic conditions than others living at the opposite end at a lower altitude.4- Migration: Migration is the movement of organisms from one location to another. Although it can occur in cyclical patterns (as it does in birds), migration when used in a population genetics context often refers to the movement of individuals into or out of a defined population.5-Random chance
What phenomenon occurs when a particular alelle will either be expressed or silenced depending on whether it is inherited from a male or female?
Genomic imprinting is the phenomenon where a particular allele is expressed or silenced depending on whether it is inherited from the mother or the father. This process is regulated by epigenetic mechanisms such as DNA methylation that affect gene expression without altering the underlying DNA sequence.
In tomatoes red fruit color is dominant to yellow and suppose a tomato plant homozygous for red is crossed with one homozygous for yellowso determine the appearance of first filial?
Let the dominant allele, red color, be represented by R,and the recessive alelle, yellow, by r. Both parent plants are homozygous, so their genotypes will be: Red: RR Yellow: rr The cross is therefore: RR X rr Remember that a homozygous genotype can produce only one type of gamete, so the red plant can only produce gametes with R, and the yellow plant can only produce r gametes. Since the F1 generation takes one gamete frrom each parent, and each parent can only produce one type of gamete, then the F1 generation can have only one genotype: F1: Rr That is, all of the offspring from this cross will be heterozygous. Red is dominant over yellow, and all of the offspring carry one R allele, therefore all of the F1 generation will be red in color.
Do genes determine inherited traits or DNA?
Dominant and recessive alleles. Genes encode for proteins, which do all sorts of functions in your cells and body as a whole. If you have a certain allele of a gene, it will code for a specific type of protein. Different alleles are why everyone looks different.
Why do the chromosomes in a homologous pair differ from one another?
They have the same length and gene locus but differ in terms of alleles. An allele is a form of a gene, differing from other alleles of the gene by a few bases at most and occupying the same locus as the other alleles of that gene. The gene locus is the position of a gene on a chromosome. Hope that helped! They have the same length and gene locus but differ in terms of alleles. An allele is a form of a gene, differing from other alleles of the gene by a few bases at most and occupying the same locus as the other alleles of that gene. The gene locus is the position of a gene on a chromosome. Hope that helped!
Can b-positive parents have child with o-positive blood?
Believe it or not, the answer is YES! Each parent carries what are known as alleles for blood protiens, which can be A, B or O. A and B are considered Dominant, and if one of them is present, the persons blood type will be the same as the domininant alelle. O is recessive, and unless neither A nor B are present for the other allele, the "O" will not be "visible". Folks that have AB blood type have codominance (one of each dominant allele). The rest of us who are either A or B (I'm A!) have one of the following combinations: AA (homozygus) Ao (Heterozygus) BB (Homozygus) Bo (Heterozygus). It's tough to draw a table in this space, but here's how it works when two people have a child (at least as far as blood type goes!) THe Mom's alleles are listed on the top here (for this example, they don't have to be) and the Dad's are listed down the left: Here we're looking at a heterozygus "A" Dominant mom and a heterozygus "B" dominant dad. Mom and dad each "donate" an allele to their child, and it can occur in one of four ways: the four possible ways are inside the square A o B AB Bo o Ao oo What this tells us is that with an A mom and a B dad, there's a 25% chance the baby will be AB, 25% chance B, 25% chance A, and 25% O. That said, here's some possibilities for the questioner: Even though I've never met them or tested their blood, I can be 100% sure that IF they truly are the parents of a type "O" baby, then they each are heterozygus dominant for the B allele (see below) B o B BB Bo o Bo oo That tells us that with two "B" parents, there's a 25% chance the offspring will be "O". As to the "Positive" or "Negative" aspect of blood type, that's a reference to the Rh factor. This is a little more complicated, but as long as one parent is positive, the baby will be positive. If both parents are positive, there's no doubt the baby will be too. So, if the questioner had said that they had an "O-" baby, I'd have to blow the whistle on that one! Congrats on the new kiddo!
