Describe a karyotype. Why do we create karyotypes? What makes two chromosomes ho
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Question
Describe a karyotype. Why do we create karyotypes? What makes two chromosomes homologous? Where does each homolog from a pair come from? How many sets of chromosomes make up a human somatic cell? a gamete? How many pairs of chromosomes make up a somatic cell? a gamete? What is meant by haploid versus diploid? Describe how the number of chromosomes, quantity of DNA, and ploidy change in a cell undergoing meiosis from G_1, to S, to G_2, to after meiosis I & cytokinesis, to after meiosis II & cytokinesis p. 2 Ch 10 notes). Distinguish what is meant by incomplete dominance (snapdragons) and codominance (ABO blood group). Which involves apparent phenotypic blending even though the alleles are not blending? Describe the genotypes and phenotypes of the ABO blood group in humans. What do the genes code for? How does this lead to the terms universal donor and receiver with respect to blood types?Explanation / Answer
Please find the answers below:
Answer 7: A karyotype represents a phyical representative of the structural and morphological features of chromosomes in a cell. The karyotype clearly shows the number of chromosomes, their shape and size along with any chromosomal abberation if present. Thus, a karyotype can be performed to assess any genetic deformity in a cell.
Answer 8: The diploid organisms contain two sets of chromosomes which contain the similar set of genes located on their linear structures. These chromosomes are structurally and morphologically similar to each other. These morphological, structural and molecular features make two chromosomes homologous in nature.
The human somatic cells are diploid in nature (2n) and contain total 23 pairs or 46 chromosomes in number. However, the gametes are haploid (n) in nature and contain only 23 chromosomes.
A haploid cell means that the chromosomes number is half of the normal number of chromosomes in an diploid cell. A diploid cell contains two copies of each chromosome whereas a haploid cell contains a single copy of them.
Answer 9: The chromosomal quantity and other details can be found as below:
Meiosis I: before division: 2n
G1: 2n
S:2n
G2:2n
M:n
Cytokinesis: n
Meiosis II: n
G1: n
S:n
G2:n
M:n
Cytokinesis: n
Answer 10: Besides the normal patterns of Mendelian inheritance, there exist some modes of inheritances which deviate from the normal methods. These patterns do not show complete dominance and hence have different genotypic and phenotypic ratios. Examples are incomplete dominance and codominance.
Incomplete dominance is the nature of genetic inheritance in which the presence of a dominant and a recessive gene does not impart the phenotype respective to the dominant gene but the phenotypes blend with each other and give rise to a new one as compared to individuals with homozygous dominant or recessive genes. For example in Snapdragon plants, the homozygous dominant flowers are red and recessive are white whereas heterozygous plants are pink in color.
Co-dominance is the mode of inheritance in which the presence of two alleles gives rise to a phenotype which expresses both the alleles completely without mixing or blending of the phenotypes respective to the two alleles. For example in human blood groups, A and B are co-dominant whereas both are completely dominant over O. Thus individuals with genotype AB have AB blood group due to co-dominance.
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