Let’s suppose you were looking through a vial of fruit flies in yourlaboratory and noticed a male fly with pink eyes. What crosseswould you make to determine if the pink allele is an X-linkedgene? What crosses would you make to determine if the pink alleleis an allele of the same X-linked gene that occurs as a white allele?

Let’s suppose you were looking through a vial of fruit flies in yourlaboratory and noticed a male fly with pink eyes. What crosseswould you make to determine if the pink allele is an X-linkedgene? What crosses would you make to determine if the pink alleleis an allele of the same X-linked gene that occurs as a white allele?

Human Biology (MindTap Course List)

11th Edition

ISBN:9781305112100

Author:Cecie Starr, Beverly McMillan

Publisher:Cecie Starr, Beverly McMillan

Chapter20: Chromosomes And Human Genetics

Section: Chapter Questions

Problem 2CT: Human sex chromosomes are XX for females and XY for males. a. With respect to an X-linked gene, how...

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Let’s suppose that you have made a karyotype of a female fruit flywith red eyes and found that it has three X chromosomes insteadof the normal two. Although you do not know its parents, you doknow that this fly came from a mixed culture of flies in whichsome had red eyes, some had white eyes, and some had eosin eyes.Eosin is an allele of the same gene that has white and red alleles.Eosin is a pale orange color. The red allele is dominant and thewhite allele is recessive. The expression of the eosin allele, however, depends on the number of copies of the allele. When femaleshave two copies of this allele, they have eosin eyes. When femalesare heterozygous for the eosin allele and the white allele, they havelight-eosin eyes. When females are heterozygous for the red alleleand the eosin allele, they have red eyes. Males that have a singlecopy of the eosin allele have eosin eyes.You cross the XXX red-eyed female with a white-eyed male andcount the numbers of offspring. You may assume that…
The X chromosome has a lot of traits for things besides the traits we consider female. It carries traits forthings like the ability of your blood to clot correctly and the ability to see differences in the colors red andgreen. If you blood doesn’t clot correctly, it’s called Hemophilia. If you can’t see the difference betweenred and green, you are colorblind. Therefore, these are referred to as X-Linked or Sex-Linked Traits.Notice that those are on the X chromosome only. That means they are missing from the Y. In fact, the Y iscalled Y because it is physically missing a section at the end. This means the Y chromosome is missing genes that the X chromosome has. If you are XY, you only haveone copy of the gene, or one allele. Given what we just said above, can a XY parent pass a X-Linked Trait to his XY offspring?
In 1952, an article in the British Medical Journalreported interesting differences in the behavior ofblood plasma obtained from several people who suffered from X-linked recessive hemophilia. Whenmixed together, the cell-free blood plasma from certain combinations of individuals could form clots inthe test tube. For example, the following table showswhether clots could form (+) or not (−) in variouscombinations of plasma from four people withhemophilia:1 and 1 − 2 and 3 +1 and 2 − 2 and 4 +1 and 3 + 3 and 3 −1 and 4 + 3 and 4 −2 and 2 − 4 and 4 −What do these data tell you about the inheritance ofhemophilia in these individuals? Do these data allowyou to exclude any models for the biochemical pathway governing blood clotting?
Let’s suppose that two different X-linked genes exist in mice,designated with the letters N and L. Gene N exists in a dominant,normal allele and in a recessive allele, n, that is lethal. Similarly,gene L exists in a dominant, normal allele and in a recessive allele,l, that is lethal. Heterozygous females are normal, but males thatcarry either recessive allele are born dead. Explain whether or notit would be possible to map the distance between these two genesby making crosses and analyzing the number of living and deadoffspring. You may assume that you have strains of mice in whichfemales are heterozygous for one or both genes.
Human sex chromosomes are XX for females and XY for males. a. With respect to an X-linked gene, how many different types of gametes can a male produce? b. If a female is homozygous for an X-linked allele, how many different types of gametes can she produce with respect to this allele? c. If a female is heterozygous for an X-linked allele, how many different types of gametes can she produce with respect to this allele?
A scientist working with Drosophila flies studies wing length, an X-linked characteristic. He has pure-breeding lines of short-winged and long-winged flies available. He decides to use reciprocal crosses for his work.i) What are reciprocal crosses? ii) Provide an example of the reciprocal crosses this scientist will do.iii) If the gene for wing length was sex-linked, but present in the pseudoautosomal region, what would you expect the outcome of a reciprocal cross to be with regards to males and females?
In fruit flies, the following X-linked traits are found: white eyes are recessive to red eyes, ebony body is recessive to gray body, and short wings is recessive to long wings. A cross was made between wild-type males with red eyes, long wings, and gray bodies and females with white eyes, short wings, and ebony bodies. Female heterozygote resulting from this cross, which had red eyes, long wings, and gray bodies, were then crossed with males with white eyes, short wings, and ebony bodies. The F2 generation data is obtained below: 1299 white eyes, short wings, ebony bodies 1367 red eyes, long wings, gray bodies 99 white eyes, short wings, gray body 89 red eyes, long wings, ebony bodies 49 white eyes, long wings, ebony bodies 49 red eyes, short wings, gray bodies 1 red eyes, short wings, ebony bodies 1 white eyes, long wings, gray bodies A) Calculate the map distance separating the three genes B) Which gene is in the middle?
You are studying ear shape in dogs (with XY se x determination) and cross a true-breeding pointed-ear female to a true-breeding floppy-ear male and collect all pointy-ear male and female offspring. Your colleague suspects that the two phenotypes may be caused by alleles of one X-linked gene. What sort of cross would you do to determine whether this is an X-linked trait? Name it and describe it. What offspring phenotypic ratio would you expect in that cross if the green allele is a dominant X-linked allele? Make sure to label your ratio with all relevant phenotypes. How would the result of your cross (from A) be different if the trait is autosomal
Female fruit flies homozygous for the X-linked white-eye alleleare crossed to males with red eyes. On very rare occasions, an offspringof such a cross is a male with red eyes. Assuming these rareoffspring are not due to a new mutation in one of the mother’s Xchromosomes that converted the white-eye allele into a red-eyeallele, explain how a red-eyed male arises.
An individual comes into your genetics clinic to be tested for any anomalies. When looking at their karyotype, you notice they have three X chromosomes and a Y chromosome. What information would you be able to relay to this individual? O They have Turner syndrome, are genetically female, and have two Barr bodies per cell. O They have Klinefelter syndrome, are genetically female, and have two Barr bodies per cell. O They have Klinefelter syndrome, are genetically male, and have two Barr bodies per cell. O They have Klinefelter syndrome, are genetically male, and have three Barr bodies per cell. O They have Turner syndrome, are genetically male, and have three Barr bodies per cell.
In the experiment of Figure shown, Stern followed the inheritancepattern in which females carried two abnormal X chromosomesto correlate genetic recombination with the physical exchange ofchromosome pieces. Is it necessary to use a strain carrying twoabnormal chromosomes, or could he have used a strain in whichfemales carried one normal X chromosome and one abnormal Xchromosome with a deletion at one end and an extra piece of the Ychromosome at the other end?
How would you set up crosses to determine if a gene is Y-linkedversus X-linked?