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BIOL239 Lecture : Chromosomes Part II Euploidy, Monoploidy, Triploidy, Tetraploidy

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School
University of Waterloo
Department
Biology
Course
BIOL239
Professor
Christine Dupont

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Document Summary

Euploids: gain or lose entire sets of chromosomes. Polyploids: euploids that carry three or more complete sets of chromosomes. Monoploids: one complete set of chromosomes (usually infertile because can"t go through meiosis. To make a monoploid does not involve fertilization. Females go through parthenogenesis: embryo develops from unfertilized gamete. Triplods are the result of mating diploids with tetraploids. Triploid plants are viable but sterile (ie. no seeds) Not fertile because during meiosis, you end up with gametes that are random variations of aneuploidy. Convert from diploid to monoploid then back again. If diploid is carrying a useful recessive allele, one can create a monoploid and see the desired phenotype immediately. Treat pollen of diploid to cold shock give nutrients and growth hormones, it will develop into monoploid plant. Clone plants by putting cells of monoploid in nutrients. Colchicine haploids go through dna replication, but spindle fiber formation is interrupted therefore mitosis doesn"t occur and haploid becomes diploid.

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Related Questions

Polyploidy is generally better tolerated in animals than it is in plants.

True
False

An autotriploid could be produced by fertilization of an egg that failed to undergo meiosis and a normal sperm from the same species.

True
False

Autotetraploids almost always produce gametes with a balanced number of chromosomes.

True
False

A key step in the formation of a fertile allopolyploid requires doubling of the number of chromosomes in a cell.

True
False

Cells of an amphidiploid contain two separate diploid chromosome sets.

True
False

Polyploidization has occurred in the evolution of vertebrate genomes.

True
Fals

A tetraploid cell can be created by nondisjunction of all the chromosomes in a diploid cell.

True
False

why are many polyploids sterile?

a. sister chromatids do not seperate correctly in meiosis2
b. extra sets of chromosomes segregate in meiosis, leading toaneuploid gametes
c. these cells are too big to fuse correctly duringfertilization
d. extra sets of chromosomes do not recombine correctly in meiosis1
e. extra sets of chromosomes do not line up correctly in meiosis1

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).