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HMB265H1 Lecture Notes - Lecture 17: Xyy Syndrome, Patau Syndrome, Centromere

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School
UTSG
Department
Human Biology
Course
HMB265H1
Professor
Belinda Chang

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HMB265H1 Full Course Notes
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HMB265H1 Full Course Notes
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Document Summary

Euploidy: complete set of chromosomes (change in whole set of chromosomes) Monoploid: n only one set of chromosomes. May lead to parthogenesis- the development of an unfertilized egg development of a haploid gamete that will result to the production of a monoploid organism. Will unmask recessive lethal traits that would have been masked if the organism was heterozygous and diploid. If the individual survives to adulthood no meiosis; sterile. Diploid: 2n- two sets of chromosomes (normal) Polyploidy (having more than the normal number of chromosome sets) Known to be associated with the size and vigor of the plant. Ex: large fruits are found to be tetraploid (apples, pears and grapes), while strawberries are found to be octaploid. Autotriploids: due to formation of aneuploidy germ cells (ie bananas) also sterile. Autotetraploids: doubling of 2n chromosome complement to 4n spontaneous doubling, usually induced by drug (colchicine), often source of new species. Allopolyploids: hybridization of two closely related species.

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Related Questions

Ploidy refers to the number of complete sets of chromosomes (genes) present in a cell. The number of chromosomes in a complete set is a fixed characteristic of a species. Humans are diploid with two sets of 23 chromosomes. Fruit flies are diploid with two sets of 4 chromosomes. Sexually reproducing organisms are diploid, each somatic cell of an organism has two complete sets ("di" is a prefix indicating 2.). To complete a life cycle and reproduce new members of a species, mating is required. Mating brings a donation from a male and a donation from a female together. However, if the male and female cells remain diploid, the fertilization will result in a tetraploid zygote. In general, these are not viable. A mechanism is needed to form special haploid cells, gametes. The diploid set is split precisely into two complete haploid sets. That mechanism is meiosis.

The complete set of chromosomes of a species is also the complete set of genes of a species, the genome. (Yes, there is a minor contribution from mitochondria and chloroplasts. Inheritance of this information is "cytoplasmic".)

Please answer the following questions:

1. How many chromosomes in a brain cell of a fruit fly? How many chromosomes are in a liver cell of a human? Explain both answers.

2. How many chromosomes are in a fruit fly unfertilized egg? How many chromosomes are in a human egg? Explain both answers.

3. Why is meiosis necessary for sexually reproducing organisms? How many chromosomes are in a human zygote? Relate the two answers.

4. What is a gene allele? Suppose there is a gene called "bingo" and it is present once in a complete haploid set. How many alleles of "bingo" does a diploid individual have? How many copies or versions of the gene "bingo" are present in a diploid individual?

5. Modern DNA sequencing clearly identifies alleles by showing the different DNA sequence of each allele. These alleles may be termed structural alleles (I coined the term for this problem.). Classical genetics only dealt with phenotypes or visible traits. As a result, alleles of genes were identified by functionality, usually normal or non-functional. Using your knowledge of gene structure and gene expression, postulate a relationship between structural alleles and functional alleles. (include relative amounts; more, less, or equal).