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Sex-linked traits

In humans, as well as in many other animals and some plants, the sex of the individual is determined by sex chromosomes—one pair of non-homologous chromosomes. Until now, we have only considered inheritance patterns among non-sex chromosomes, or autosomes. In addition to 22 homologous pairs of autosomes, human females have a homologous pair of X chromosomes, whereas human males have an XY chromosome pair. Although the Y chromosome contains a small region of similarity to the X chromosome so that they can pair during meiosis, the Y chromosome is much shorter and contains fewer genes. When a gene being examined is present on the X, but not the Y, chromosome, it is X-linked    .

Eye color in Drosophila , the common fruit fly, was the first X-linked trait to be identified. Thomas Hunt Morgan mapped this trait to the X chromosome in 1910. Like humans, Drosophila males have an XY chromosome pair, and females are XX. In flies the wild-type eye color is red (X W ) and is dominant to white eye color (X w ) ( [link] ). Because of the location of the eye-color gene, reciprocal crosses do not produce the same offspring ratios. Males are said to be hemizygous    , in that they have only one allele for any X-linked characteristic. Hemizygosity makes descriptions of dominance and recessiveness irrelevant for XY males. Drosophila males lack the white gene on the Y chromosome; that is, their genotype can only be X W Y or X w Y. In contrast, females have two allele copies of this gene and can be X W X W , X W X w , or X w X w .

Photo shows two fruit flies, one with red eyes and one with white eyes.
In Drosophila , the gene for eye color is located on the X chromosome. Red eye color is wild-type and is dominant to white eye color.

In an X-linked cross, the genotypes of F 1 and F 2 offspring depend on whether the recessive trait was expressed by the male or the female in the P generation. With respect to Drosophila eye color, when the P male expresses the white-eye phenotype and the female is homozygously red-eyed, all members of the F 1 generation exhibit red eyes ( [link] ). The F 1 females are heterozygous (X W X w ), and the males are all X W Y, having received their X chromosome from the homozygous dominant P female and their Y chromosome from the P male. A subsequent cross between the X W X w female and the X W Y male would produce only red-eyed females (with X W X W or X W X w genotypes) and both red- and white-eyed males (with X W Y or X w Y genotypes). Now, consider a cross between a homozygous white-eyed female and a male with red eyes. The F 1 generation would exhibit only heterozygous red-eyed females (X W X w ) and only white-eyed males (X w Y). Half of the F 2 females would be red-eyed (X W X w ) and half would be white-eyed (X w X w ). Similarly, half of the F 2 males would be red-eyed (X W Y) and half would be white-eyed (X w Y).

Art connection

This illustration shows a Punnett square analysis of fruit fly eye color, which is a sex-linked trait. A red-eyed male fruit fly with the genotype X^{w}Y is crossed with a white-eyed female fruit fly with the genotype X^{w}X^{w}. All of the female offspring acquire a dominant X^{W} allele from the father and a recessive X^{w} allele from the mother, and are therefore heterozygous dominant with red eye color. All the male offspring acquire a recessive X^{w} allele from the mother and a Y chromosome from the father and are therefore hemizygous recessive with white eye color.
Crosses involving sex-linked traits often give rise to different phenotypes for the different sexes of offspring, as is the case for this cross involving red and white eye color in Drosophila . In the diagram, w is the white-eye mutant allele and W is the wild-type, red-eye allele.

What ratio of offspring would result from a cross between a white-eyed male and a female that is heterozygous for red eye color?

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Concepts of biology for the university of georgia. OpenStax CNX. Aug 09, 2013 Download for free at http://legacy.cnx.org/content/col11520/1.5
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