Spectral karyotyping of human chromosomes utilizing differentially labeled “painting” probes.

1. Nondisjunction during the first and second meiotic divisions. In both cases, some of the gametes that are formed either contain two members of a specific chromosome or lack that chromosome. After fertilization by a gamete with a normal haploid content, monosomic, disomic (normal), or trisomic zygotes are produced.

2. Spectral karyotyping of human chromosomes utilizing differentially labeled “painting” probes.

3. karyotype and a photograph of a child exhibiting cri-du-chat syndrome (46,5p–). In the karyotype, the arrow identifies the absence of a small piece of the short arm of one member of the chromosome 5 homologs

4. Down Syndrome Karyotype - three members of the G-group chromosome 21 are present, creating the 47,21+ condition.

6. The karyotype and phenotypic depiction of an infant with Patau syndrome, where three members of the D-group chromosome 13 are present, creating the 47,13+ condition

7. chromosome origins of an autopolyploid versus an allopolyploid karyotype

8. The potential involvement of colchicine in doubling the chromosome number. Two pairs of homologous chromosomes are shown. While each chromosome had replicated its DNA earlier during interphase, the chromosomes do not appear as double structures until late prophase. When anaphase fails to occur normally, the chromosome number doubles if the cell reenters interphase.

9. The origin and propagation of an amphidiploid. Species 1 contains genome A consisting of three distinct chromosomes, a1, a2 and a3. Species 2 contains genome B consisting of two distinct chromosomes, b1 and b2. Following fertilization between members of the two species and chromosome doubling, a fertile amphidiploid containing two complete diploid genomes (AABB) is formed.

11. Polyploids are more vigorous than their diploid progenitors and both auto- and allopolyploids have built in mechanisms for mantaining high levels of heterozygoisty. This polyploids may exhibit a phenomenon similar to hybrid vigor, or heterosis.Hybrid vigor, also known as heterosis, is an agriculturally important phenomenon describing the observation that the hybrid offspring of two inbred genetically different varieties produces higher yields than either one of the two parental lines

13. A mule is the offspring of a male donkey and a female horse.Horses and donkeys are different species, with different numbers of chromosomes. Of the two F1 hybrids between these two species, a mule is easier to obtain than a hinny Reproductive success occurs more often when a donkey is the sire and the horse is the dam. Sometimes people let a stallion (male horse) run with a jenny (female donkey) for as long as six years before she becomes pregnant. Mules and hinnies are almost always sterile The sterility is attributed to the differing number of chromosomes of the two species: donkeys have 62 chromosomes, whereas horses have 64.

14. The mule possesses the sobriety, patience, endurance and sure-footedness of the donkey, and the vigour, strength and courage of the horse. Operators generally find mules preferable to horses: mules show less impatience under the pressure of heavy weights.. Mules are generally less tolerant towards dogs than horses are. They are also capable of striking out with any of their hooves in any direction, even sideways if needed. … Mules exhibit a higher cognitive intelligence than their parent species - horses and donkeys. …the stereotype of the mule as being stubborn is somewhat unfair and inaccurate.

15. There are no recorded cases of fertile mule stallions Mules and Hinnies have 63 chromosomes that are a mixture of one from each parent. The different structure and number usually prevents the chromosomes from pairing up properly and creating successful embryos. There are no recorded cases of fertile mule stallions.[A few female mules have produced offspring when mated with a purebred horse or donkey… Since 1527 there have been more than 60 documented cases of foals born to female mules around the world.[9] In 2007 a mule named Kate gave birth to a mule son in Colorado. Blood and hair samples were tested verifying that the mother was a mule and the colt was indeed her offspring.

16. Vol. 47, No. 3 1988  Free AbstractArticle (PDF 2894 KB) A fertile mule and hinny in ChinaR. Ronga, A.C. Chandleyb, J. Songa, S. McBeathb, P.P. Tana, Q. Baia, R.M. Speedb Anecdotal reports of fertility in female mules (jack donkey × mare) and hinnies (stallion × jenny donkey) have appeared in the literature over the years, but scientists have generally regarded them with scepticism. The fact that some of these hybrids can come into estrous and ovulate makes fertility conceivable, given that opportunity for mating arises. In China, where mules are bred extensively for work on the farms, a fertile female mule and a fertile female hinny have now been verified by chromosomal investigation. Each had mated with a donkey and produced a filly foal. The foals show unique hybrid karyotypes different from the mule's or hinny's and different from each other's. The studies make it clear that mule and hinny fertility, at least for the female hybrid, is a real possibility.

17. An overview of the five different types of rearrangement of chromosome segments.

18. Origins of • a terminal and (b) an intercalary deletion. • In (c), pairing occurs between a normal chromosome and one with an intercalary deletion by looping out the undeleted portion to form a deletion (or compensation) loop.

19. Duplicated and Deficient Regions of Chromosomes The origin of duplicated and deficient regions of chromosomes as a result of unequal crossing over. The tetrad on the left is mispaired during synapsis. A single crossover between chromatids 2 and 3 results in the deficient (chromosome 2) and duplicated (chromosome 3) chromosomal regions shown on the right. The two chromosomes uninvolved in the crossover event remain normal in gene sequence and content.

20. Losses and Gains of Gene Copies as a Result of Unequal Crossing-Over in Family of Tandemly Repeated Genes.This may be a general feature as long regions of homologous DNA sequence are favorable situations for genetic recombination.After Alberts, B. et al. Molecular Evolution of the Cell. Garland.

21. Hemoglobin is necessary to allow multicellular animals to grow to a large size, since large animals could no longer rely on the simple diffusion of oxygen. Hemoglobinlike molecules are found in all vertebrates and in many invertebrates. The hemoglobin molecule in higher vertebrates, however, is composed of two kinds of globin chains. It appears that about 500 million years ago, during the evolution of higher fish, a series of gene mutations and duplications occurred. These events established two slightly different globin genes, coding for the α- and β-globin chains.

22. . The scheme emphasizes the β-like globin gene family. A relatively recent gene duplication of the γ-chain gene produced γG and γ A, which are fetal β-like chains of identical function Still later, during the evolution of mammals, the β-chain gene apparently underwent mutation and duplication to give rise to a second β-like chain that is synthesized specifically in the fetus. The resulting hemoglobin molecule has a higher affinity for oxygen than adult hemoglobin and thus helps in the transfer of oxygen from the mother to the fetus. The gene for the new β-like chain subsequently mutated and duplicated again to produce two new genes, epsilon and γ, the epsilon chain being produced earlier in development (to form α2epsilon2) than the fetal γ chain, which forms α2γ2 (see Figure9-52). A duplication of the adult β-chain gene occurred still later, during primate evolution, to give rise to a δ-globin gene and thus to a minor form of hemoglobin (α2δ2) found only in adult primates

23. The duplication genotypes and resultant Bar eye phenotypes in Drosophila. Photographs show two Bar eye phenotypes and the wild type(B+/B+).

24. Pericentric Inversion

25. The effects of a single crossover within an inversion loop in (a) a paracentric inversion, where two altered chromosomes are produced: one acentric and one dicentric. Both chromosomes also contain duplicated and deficient regions. The effects of this crossover in (b), a pericentric inversion, produces two altered chromosomes, both with duplicated and deficient regions.

26. (a) Possible origin of a reciprocal translocation. (b) Synaptic configuration formed during meiosis in an individual that is heterozygous for the translocation.

28. Chromosomal involvement and translocation in familial Down syndrome. The photograph shows the relevant chromosomes from a trisomy 21 offspring produced by a translocation carrier parent.