Lab 7 Biology Review Essay

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BIO 105­160 Chapter 9/Lab 7 Homework Review Questions 1. What is a sex­linked trait? Why are more males than females affected by X­linked recessive traits? With your answer in mind, what must be true for a particular X­linked recessive trait to be expressed in a female? Sex­Linked trait: Sex linkage is the phenotypic expression of an allele related to the chromosomal sex of the individual. Men have one chromosome and women have two. This means, that men are more affected by X linked recessive disorder as they only have one chance to get a non­mutant allele. In humans, men are more affected and women are carriers. Here are two reasons; the first is that the simple statistical fact that if the X­linked mutation of ‘f’ (For example, 1%) then that will be the…show more content…
What does the Law of Independent Assortment describe? What is the expected phenotypic ratio of a dihybrid cross of two heterozygous parents according to this law? Apply the law to the example given in class of students lining up in pairs and also explain how this contributes to genetic diversity. Independent assortment describes that during gamete formation in an F2 cross, a particular allele for one character can be paired with either allele of another character. An example would be a cross between two plants with two characters, R and Y. If their genotypes are RRYY and rryy, R can be paired with Y or r and y can be paired with R or Y. 5. What is meant by the terms allele and locus? Make sure to mention homologous chromosomes in your answer. Allele includes one member of a pair of trait (or any of the series) of genes occupying a specific spot on a chromosome that control the same trait. When the alleles are identical, the individual is homozygous. On the other hand, a locus (position) is a specific location of a gene along a chromosome. 6. What is a testcross and how can it be used to determine genotype? (Hint: what can you OBSERVE as a result of a testcross and how does this allow you to determine genotype?) A testcross is
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