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AP Biology help please??!!?

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❶With human families, this type of "out-crossing" is the norm.

Other Model Systems Used in Genetics

Drosophila as a Model System


So I'll be using these for my punnet squares: I'll have to round the phenotype ratio to 1: Since white eye is recessive, only males have the white eye, and males only have the white eye, that leaves us with the female being homozygous for the white eye gene, since we know that the father parent can not pass the X chromosome to his sons.

Otherwise we'd have some wild type males. We have no white eye females either, so that tells us the male parent has wild-type eyes. I'm not entirely sure about answer b, but I'll give it a go with a math equation. Figure out the rest on your own: Now do the easy stuff on your own look in your text book. I have the same thing.

Mutations are easy that'ss what I started with. Basically start with explaining that a mutation is essentially a genetic typo. I used addition and deletion as my toopossiblee mutations in the lab. For the rest i'm screwed please help. Which AP class is harder: Answer Questions Do particular ions accumulate in the CV? What ions can the cell afford to expel without disturbing ion balance? Do you know how scientists clone animals? What is the process?

If the superior oblique is contracted, the eye will rotate to the? Can some one help me find General biology course exams? The normal eye color for Drosophila melanogaster is red, as shown in the photograph above from the Wikipedia Commons collection.

There are mutant varieties with brown eyes. What is the basis for the brown color, and how is this phenotype inherited? In the absence of any information about red or brown eyes, we probably cannot even begin to phrase a hypothesis that states our current understanding. Nor can we make reasonable predictions based on such an hypothesis. We can, however, ask a question experimentally.

We can ask whether the brown-eye phenotype is dominant or recessive or somewhere in-between to the normal red eye color.

We can "ask this question experimentally" by crossing red-eyed flies to brown-eyed flies, and examining the offspring.

Starting with true-breeding stocks of flies to ensure there are no unexpected genetic variations to confuse us , we see the following: It doesn't matter whether the male has brown eyes as shown here , or whether the female has brown eyes. The offspring all have red eyes. This tells us that this allele of the gene responsible for brown eyes is recessive to the normal allele found in wild flies. This allele causes eyes to be brown; therefore, the gene has been named brown. There are many different alleles of this gene, including the original allele from flies captured in the wild.

Here, we are working with the mutant allele of brown that was found first; using the convention of Drosophila genetics, the allele name or number is indicated as a superscript. Thus, brown-1 would be indicated as brown 1. Using these conventions, we can write the cross illustrated above as:.

Assuming that flies--like humans, sheep, dogs, and peas--inherit one set of genes from the mother and another set from the father, the parents should be homozygous for their particular brown alleles likely, since the strains of flies "breed true". If this is really true, we can make several clear predictions:.

To test prediction 2, we must perform the following cross: The flies represented in the bottom row will have brown eyes. Two squares in the top row, two in the bottom row, and we get This result is consistent with our expectation. Drawing this out in a Punnett Square is the easiest way to see what's happening in this cross:. We expect 1 out of 4 offspring to be homozygous for brown 1 lower right corner of the table.

What do we find when we do the cross? The data we obtain from these crosses appear to support our hypothesis--our understanding of how the brown gene is inherited.

This allele appears to be inherited as a simple recessive allele. Despite the genetic analysis, we don't yet understand the link between genotype and phenotype here.

There are several models that we can imagine--from brown 1 flies failing to produce a red pigment, to brown 1 flies over-producing a brown pigment due to some kind of biochemical problem.

We need more information before we can understand how the brown 1 mutation causes fly eyes to be brown. What about the inheritance of white eyes, the first mutant Drosophila found by TH Morgan in ? TH Morgan named the gene white. Again, we have no understanding of how this mutation might be inherited, so there is little point in guessing.

Let's start by asking the simple question: Again, we will ask this question experimentally, by crossing wild type, red-eyed flies with mutant, white-eyed flies. Again, just to be sure we don't overlook something interesting, we will perform the cross both ways--with white-eyed males, or with white-eyed females. The results are as follows:. The results of cross A are what we would expect if the white 1 allele is inherited as a simple recessive. But the "reverse" cross, B , is very different.

Somehow, the sex of the fly matters. To figure this out, it might be necessary to look into the mechanisms that determine sex. In crocodiles and some species of turtles, sex is determined by the temperature at which the eggs develop.

In some species, a warm nest produces all females, and a cold nest produces all males. In other species, it's the other way around. But in fruit flies and mammals, the temperature has no effect. Sex determination occurs genetically, in response to certain genes that control embryological development. In species with genetic sex determination, there is often a visible difference in the chromosomes of males and females. This is true in humans and in Drosophila.

For both of us, most of the chromosomes are identical in both males and females though they may carry slightly different alleles. This is easiest to see in Drosophila , which have only 4 chromosome pairs compared to humans, with 23 pairs.

The image shown here redrawn from J. Albert Vallunen's photograph s in the Wikimedia Commons shows chromosomes condensed at metaphase of mitosis. In Drosophila , mitotic chromosomes often associate in pairs, with the tiny chromosome 4 in the center of the cluster. It is evident from looking at the chromosomes that females have two X chromosomes, while males have only one. Instead of a pair of X's, males have an X chromosome paired with a Y chromosome. The situation is similar in humans: XX individuals develop as females, and XY individuals develop as males.

The presence of X and Y chromosomes leads us to ask an interesting question: What happens with genes that are located on the X chromosome or on the Y chromosome? But what if genes are on the sex chromosomes? In humans, there is a gene on the Y chromosome that regulates the "hair-growth program" specifically in ears. Most alleles of this gene result in little or no ear hair.

Some alleles, however, activate the hair growth program, resulting in hairy ears. The image on the right is hosted at http: Because the Y chromosome also carries the gene that determines maleness, the hairy-ear phenotype rarely, if ever, occurs in women.

The white-eye phenotype in Drosophila does occur in female flies. This observation rules out the possibility that the white gene might be on the Y chromosome.


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Jan 02,  · In fruit flies the phenotype for eye color is determined by a certain locus. E indicates the dominant allele and e indicates the recessive allele. The cross between a male wild-type fruit fly and a female white-eyed fruit fly produced the following blueberryhusky.ga: Resolved.

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(a) Determine the genotypes of the original parents (P generation) and explain your reasoning. You may use Punnett squares to enhance your description, but the results from the Punnett squares must be discussed in your answer. (b) Use a Chi-squared test on the F2 generation data to analyze your prediction of the parental genotypes.

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1/2/ PM In fruit flies, the phenotype for eye color is determined by a certain locus. E indicates the dominant allele and e indicates the recessive allele. In fruit flies, the phenotype for eye color is determined by a certain locus. E indicates the dominant allele and e indicates the recessive allele.

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In fruit flies, males are determined by the presence of an X and Y chromosome; females are determined by two X chromosomes. The gene for eye color is located on the X chromosome and is absent from the Y chromosome. The allele for white eyes is recessive and the allele for red eyes is dominant. AP® BIOLOGY FREE-RESPONSE QUESTIONS In fruit flies, the phenotype for eye color is determined by a certain locus. In fruit flies, the phenotype for eye color is determined by a certain locus. E indicates the dominant allele and e indicates the recessive allele. The cross between a male wild-type fruit fly and a female white-eyed fruit.