Use a separate sheet of paper to answer the following questions if needed. Show
ID: 258788 • Letter: U
Question
Use a separate sheet of paper to answer the following questions if needed. Show all of you wPk muia all genotypes and phenotypes, where appropriate. If more than one type of offspring is produced, indicate the proportion of each type. 1. During what phase of mitosis are chromosomes collected for the purposes of making a ka a. What occurs during this phase that provides the best chromosomesi 2. What kind of cells are commonly used for obtaining the chromosomes needed for a karyotype? A man with recessive attached ear lobes mates with a woman who is heterozygous for free ear lobes. What types of offspring and what proportion of each type would be expected from this mating? 3. Polydactyly is an inherited human trait in which the affected individual has extra fingers or toes. This defect results from the dominance of the defective gene (G) over the normal allele (o). a. Ifa man with polydactyly (assume that he is heterozygous) mates with a normal woman, what 4. are the possible genotypes of their children?Explanation / Answer
1) Mitotic cells that have been arrested in the prometaphase or metaphase stage are used for making karyotype charts. This is the phase when chromosomes are most condensed and are easily visible.
a) During metaphase, the chromosomes are most condensed and are easily visible on the equator of the metaphasic plate. It is easy to count the number of chromosomes and to deduce their structure in this stage which makes it suitable for creating a karyogram.
2) Karyogram can be obtained from a number of tissues. For cancer diagnosis, tissue biopsy cells or bone marrow cells are used for making karyotype. For other diagnoses, karyotypes are often generated from peripheral blood specimens or a skin biopsy. For prenatal diagnosis , amniotic fluid or chorionic villus specimens are used as the source of cells.
3) Earlobes are directed by the expression of two alleles, E and e, with E denoting the dominant phenotype of free earlobes and 'e' denoting the recessive phenotype of attached earlobes. Following combinations of alleles can be present at a given time:
Now, Given in the question, that the man has recessive attached lobes, hence his genotype will be 'ee', and woman is heterozygous for free earlobes, hence her genotype will be 'Ee'. The cross between these two will result in following genotypes:
Thus, 50% of the offsprings will be heterozygous for free earlobes and 50% will be have recessive attached earlobes.
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