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32 Cards in this Set
- Front
- Back
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What type of chromosome group cause abnormality such as sterility or even death in most cases?
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Aneuploidy
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Gene mutations are one source of genetic change, what are two others?
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Large-scale alterations to chromosome structure. Changes in chromosome number or numbers of chromosome sets.
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In what ways are large-scale chromosomal changes useful in the study of genetics?
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Show how genes act in concert on a genomic scale.
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describe chromosomal mutations
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They are due to changes in chromosome number in a cell. They cause inheritable phenotypes.
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A cell or organism having more than two sets of chromosomes.
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Polyploid
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An allotetraploid was formed through hybridization between two parental species, one with haploid number n1 = 3, and the other with n2 = 2. How many chromosomes would you see in the somatic cells of the hybrid? Draw a diagram showing the pairing configuration of the chromosomes you would expect to see in Prophase of Meiosis I.
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The diploid number would be 2n1 + 2n2 = 10, so you would see 10 chromosomes in the somatic cells of the hybrid.
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When an allotetraploid is backcrossed to one of its progenitor species, a sterile progeny is produced. This individual can be best represented by:
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2n1 + n2
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An allotetraploid plant with 2n = 30 is backcrossed to one of its progenitor species that has an n = 8. A sterile progeny is produced. How many chromosomes will this sterile individual possess, and what are the chromosome numbers of the two progenitor species?
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The allotetraploid can be represented as 2n = 2n1 + 2n2. Let n2 = 8, so 2n1 + 16 = 30, therefore n1 = 7. The chromosome complement of the sterile progeny is 2n1 + n2 = 14 + 8 = 22.
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form of euploidy
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2n
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Why do most polyploidy species tend to have even numbers? How would you account for the appearance of individuals with an odd number of chromosomes (that is, 21, 39, etc.) in series of polyploidy species with 2n = 20, 40, 60, 80?
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Polyploids with an even number of chromosomes are more likely to have a regular meiosis than those with an odd number, and so are more likely to be fertile. These specimens represent the occasional aneuploid. For instance, the one with 21 chromosomes would have one extra chromosome, and the one with 39 chromosomes would lack one. Nondisjunction would be the cause in both cases.
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What would be the consequence of applying the chemical colchicine at the second meiotic division instead of before the first? Would this be of any use for producing polyploids?
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You would prevent the sister chromatids from separating
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An allopolyploid formed from the union of two separate chromosome sets and their subsequent doubling.
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Amphidiploid
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You make meiotic chromosome preparations of two species of tetraploid plants. In one there is normal pairing of chromosomes and tetrads (quadivalents) are observed, while in the other there is abnormal pairing in some preparations and trivalents and univalents are seen. How would you account for the differences between these two species?
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The first is an allotetraploid and the chromosomes from the two progenitor species pair independently and normally. The other is an autotetraploid and so there are four homologous chromosomes that have to pair in Prophase I. This often leads to unusual pairing and trivalents and univalents will be seen.
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You observed two species of plants that are very similar and are obviously closely related. One is consistently larger than the other in its structures, fruit, etc. What is a possible explanation for this?
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The larger species is probably a polyploidy as polyploids generally tend to be larger than their diploid progenitors
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Why are polyploids with an even number of chromosomes generally fertile, while polyploids with an odd number of chromosomes infertile?
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When there is an odd number of chromosome sets in a polyploidy the gametes and the subsequent offspring are aneuploid
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Organisms containing which chromosome numbers are likely to be sterile?
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n
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A small dividing mass of monoploid cells derived from a pollen grain.
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Embryoid
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The development of an individual from an egg without fertilization
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Parthenogenesis
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Distinguish between monsomy and trisomy
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Monosomy = the condition of a cell or individual lacking one of the homologs from a normal pair. The chromosome number is then 2n – 1.
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An abnormal human phenotype, including mental retardation, due to trisomy of chromosome 21.
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Down syndrome
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The abnormal human phenotype resulting from the possession of an extra X chromosome (XXY).
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Klinefelter syndrome
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The equalization of expression sex-linked genes between males and females in organisms with a chromosomal system of sex determination, such as XX-XY.
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Dosage compensation
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A cell or individual that has only one copy, instead of two, of a particular chromosome.
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Monosomic
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A cell or individual that has three copies of a particular chromosome instead of two.
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Trisomic
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An association of three homologous chromosomes in meiosis.
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Trivalent
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What is one possible biological consequence of segmental duplications?
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Segmental duplications are thought to function as substrates in non-allelic homologous recombination that can result in chromosomal re-arrangements, which in turn may result in evolutionary changes in genomes. Some human diseases are results of segmental duplications.
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The type of inversion that does not include the centomere.
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Paracentric
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The type of inversion that includes the centromere.
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Pericentric
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Aberrant euploidy
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whole chromosome sets
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Balanced Chromosomal Rearrangements
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Balanced rearrangements changes in gene order, but not gene quantity
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unBalanced Chromosomal Rearrangements
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Unbalanced rearrangements changes in gene content or quantity
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