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A female heterozygous drosophila melanogaster with the x linked genes of singed bristles (sn), crossveinlesss wings (cv), and vermillion eye colour (v) is testcrossed with a singed, crossveinless, vermillion male and the following progeny were obtained:

1 singed, crossveinless, vermillion 3
2 crossveinless, vermillion 392
3 vermillion 34
4 crossveinless 61
5 singed, crossveinless 32
6 singed, vermillion 65
7 singed 410
8 wildtype 3

total 1000

a) what is the order of these genes on the X chromosome
b) what are the genetic map distances between sn & cv; sn & v; and cv & v
c) what is the coefficient of coincidence

I need a lot of detailed explanations.

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In drosophila, sex is determined by the number of X chromosomes. In this question, since they didn't tell us how many X's each fly has, we can assume that the female has 2 X chromosomes, and the male has 1.

We know that the female is heterozygous, so she has different alleles for each gene on her 2 X chromosomes. The male only has one copy of each gene. I know that vermillion eyes and crossveinless wings are both recessive genes, and I can only assume that singed bristles are as well. So, a fly can only show these traits if they only have the recessive allele (symbolized below using a -) and not the dominant allele (symbolized below using a +).

The alleles can be symbolized as:
sn- = singed bristles
sn+ = non-singed bristles
cv- = crossveinless wings
cv+ = wings with crossveins
v- = vermillion eyes
v+ = non-vermillion eyes

The female has genotype sn+ sn- cv+ cv- v+ v- She is wild-type.

The male has genotype sn- cv- v- He is singed, crossveinless, and vermillion.

a) what is the order of these genes on the X chromosome?

There ...

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From these 3 alleles, there are 4 blood types (phenotypes): A, B, AB, and O, and there are six genotypes: AA, Ao, BB, Bo, AB, or oo. This is an example of codominance in which both A and B alleles are codominant to each other.

Blood types can be used in forensics to determine if blood is from the victim or criminal. Blood types can be used to determine parental source in situation where the father is unknown; however, blood types can only eliminate certain blood types. DNA fingerprinting is a better method that is used often in criminal and parental determination cases.

A o



Punnett squares such as the one shown above are used to determine the probabilities (percentages) for genotypes of offspring given specific genotypes for the parents.

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Eukaryotic cells can divide by mitosis or meiosis. In humans, mitosis produces new cells for growth and repair. And, meiosis produces sex cells (gametes), called sperm and eggs. Changes or mutations in genes in sex cells can be inherited by human offspring. Genetic variation in a population of organisms is good; however, sometimes mutations can be harmful or cause genetic disorders.

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