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Topic: Y-chromosomes

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A Chromosome Study Sex chromosomes determine the sex of the individual.Ý A female develops when the sex chromosomes match--XX.ÝÝ A male develops if the two sex chromosomes are unmatched--XY.Ý (These chromosomes are unshaded on your karyotype) The HAPLOID CHROMOSOME NUMBER refers to the number of chromosomes in an organisms sex cells.Ý Sperm in males, eggs in females.Ý The haploid number, or 1n number is always -half- that of the diploid number. 2.Ý How many chromosomes are present in each cell of this human?ÝÝ _____________ www.biologycorner.com /worksheets/Chromosomestudy.htm   (549 words)

Abnormal tissue-dependent polytenization of a block of chromosome 3 pericentric heterochromatin in Drosophila melanogaster -- Koryakov et al. 116 (6): 1035 -- Journal of Cell Science Abnormal tissue-dependent polytenization of a block of chromosome 3 pericentric heterochromatin in Drosophila melanogaster -- Koryakov et al. Genetic analysis of the heterochromatin of chromosome 3 in Drosophila melanogaster. Genetic analysis of the heterochromatin of chromosome 3 of Drosophila melanogaster. jcs.biologists.org /cgi/content/full/116/6/1035   (549 words)

CHAP5.DAT Remember that the resulting tetravalent structure can separate by alternate segregation (yielding normal chromosomes - hence black spores) or by adjacent segregation (yielding chromosomes with duplicted and deleted sections - hence white spores). This cross therefore produces a translocation heterozygote and at meiosis four chromosomes pair together, normal chromosomes 2 and 6 + two translocated chromosomes each carrying parts of chromosomes 2 and 6. After alternate segregation half of the progeny carry normal chromosomes and half translocated chromosomes. www.rpi.edu /locker/53/001053/CHAP5.DAT   (549 words)

Hurst - Creative Evolution Polyploid species, however, differ fundamentally from polyploid varieties, inasmuch as their polyploid sets of chromosomes and genes are those of more than one diploid species while polyploid varieties have the chromosomes and genes of a single diploid species. The unequal polyploid species with unbalanced (bivalent and univalent) chromosomes consisting of 7 bivalents and either 7, 14, 21 or 28 univalents have an irregular meiosis followed by a regular but unequal gametogenesis in which the female gametes have twice, three times or four times the number of chromosomes found in the functional male gametes. With regard to the unequal polyploid species with unbalanced bivalent and univalent chromosomes: omitting those with more than one septet of bivalents which are natural hybrids and omitting triploids which are not found in a wild state as established species, 55 polyploid septet species are possible, viz. www.bulbnrose.com /Roses/Hurst/HURST.HTM   (2599 words)

New Scientist Breaking News - Platypus sex is XXXXX-rated The extra chromosomes in the monkey are probably due to a hiccup in evolution whereby non-sex chromosomes mutated to become sex chromosomes. The chromosomes at one end of the platypuses’ chromosome chain shares similarities with mammalian sex chromosomes, while the other end shares characteristics with the sex chromosomes of birds. The way in which chromosomes determine sex in mammals and birds was thought to have evolved independently after the two classes diverged 300 million years ago. www.newscientist.com /article.ns?id=dn6568   (543 words)

Plant Hybrids #1 In addition, Niehaus states that "no meiotic irregularities or quadrivalents were observed in any polyploids." Normally homologous chromosomes pair up in 2's (bivalent) during synapsis of meiosis I. If homologous chromosomes associate in 4's rather than 2's, this is called a quadrivalent. Quadrivalent chromosome arrangements result in gametes with twice as many chromosomes and polyploids with higher numbers of chromosomes. n the formation of gametes during normal meiosis, homologous chromosomes must pair up with each other during synapsis of prophase I. Like other odd polyploids (with 3 sets of chromosomes), bananas are sterile and seedless because one set of chromosomes (A or B) has no homologous set to pair up with during synapsis of meiosis. waynesword.palomar.edu /hybrids1.htm   (6131 words)

Meiosis - Wikipedia, the free encyclopedia Without the halving of ploidy, or chromosome count, fertilization would result in zygotes that have twice the number of chromosomes than the zygotes from the previous generation. Meiosis uses many biochemical processes that are similar to those used in mitosis in order to distribute chromosomes among the resulting cells; however the outcome is very different. At the same time during meiosis I, when the chromosomes are pairing up together for a short time before being separated during synapsis, chromosomal crossover occurs. en.wikipedia.org /wiki/Meiosis   (2390 words)

HURST2.HTM The hexaploid species with three double septets of chromosomes and characters are found further south, and where they extend far are usually at high altitudes. Each has a septet of chromosomes which is double in the somatic cells and single in the gametes and presumably the five differential sets of taxonomic characters are represented in the five corresponding differential septets of chromosomes. (5) All hybrids between regular tetraploid and diploid species with different septets should have the septet characters of the corresponding hexaploid species, but their chromosomes should be triploid (21). www.geocities.com /kingke.geo/Hurst/HURST2.HTM   (2390 words)

Herschel L. Roman, September 29, 1914—July 2, 1989 By Michael S. Esposito Biographical Memoirs Controlled breeding experiments between strains that contain no B-type chromosomes and strains containing one or two B-type chromosomes suggested that mitotic nondisjunction of B-type chromosomes occurs at high frequency during one or both of the postmeiotic mitotic divisions that comprise pollen grain formation in maize. Moreover, there was no evidence of meiotic nondisjunction of B-type chromosomes that might explain the numerical variation in the number of B-type chromosomes per plant. Mitotic nondisjunction of B-type chromosomes during pollen grain development coupled with directed fertilization of the seed parent egg nucleus by the hyperhaploid 2B gametic nucleus maintains B-type chromosomes in maize populations. www.nap.edu /readingroom/books/biomems/hroman.html   (2390 words)

Genetics and Molecular Biology - Did Sutton and Boveri propose the so-called Sutton-Boveri chromosome hypothesis? Sutton asserted that he made a more careful study of the cell division process, especially chromosome position before division, spindle origin and formation, the relative positions of chromosomes and centrosomes, and the contact between spindle fibers and chromosomes. However, Wilson himself described Boveri's contribution as: "Boveri had provided two of the fundamental postulates of Sutton's theory, namely, the individuality or genetic continuity of the chromosomes (which he had done more than any other to establish) and especially their qualitative differences in respect to development, for which he alone was responsible" (Wilson, 1925, p. Sutton detected 23 chromosomes in diploid cells of Brachystola magna; one was called an `accessory chromosome' (X). www.scielo.br /scielo.php?script=sci_arttext&pid=S1415-47571999000200022&lng=en&nrm=iso   (2390 words)

Open Biosystems: Molecular Biology - STAR*FISH Chromosome Paints-Human - Human Rainbow FISH Probes Human Rainbow*FISH probes visualize 6 chromosomes per set (1-6, 7-12, 13-18 and 16-Y). All STAR*FISH paint systems for whole human chromosomes are Cot-1 free and they are prepared from DOP-PCR-amplified DNA obtained from FACS-sorted chromosomes. The STAR*FISH system provides an excellent method for the identification of single human chromosomes, and allows the detection of translocations and insertions on metaphase chromosomes. www.openbiosystems.com /human_rainbow_fish_probes.php   (2390 words)

BGN 12: Effects of cycloheximide treatments on prophase and metaphase cells of a (2X) Hordeum vulgare X (2X) H. bulbosum hybrid In the metaphase cell shown in Figure 4 satellite chromosomes were observed in the center of the cell while other chromosomes, some having undergone centromere separation, were displaced to the periphery of the cell. In roots treated for 1 h with cycloheximide and allowed to recover for 2 hours in water metaphase cells were observed with varying numbers of non-congressed chromosomes. These observations suggest that treatment with cycloheximide disturbs the congression of the bulbosum chromosomes onto the metaphase plate and that this may eventually result in the elimination of these chromosomes (Wheatley, Noda and Kasha, unpublished observations). wheat.pw.usda.gov /ggpages/bgn/12/12p72.html   (624 words)

Molecular Cytogenetics and Genome Organization - Pat Heslop-Harrison In contrast, similar data from metaphase chromosomes of A. cepa suggests that although retrotransposon sequences are dispersed throughout the euchromatic regions of the genome, they are predominantly concentrated in the terminal heterochromatin. In situ hybridisation data from metaphase and prophase chromosomes of V. faba, S. cereale and H. vulgare suggest that retrotransposon sequences are dispersed throughout the euchromatic regions of the genome but are almost undetectable in most heterochromatic regions. In situ hybridization of labelled A and B genomic DNA to metaphase chromosomes of triploid AAB and ABB cultivars discriminated between A and B genome chromosomes. www.le.ac.uk /biology/phh4/titleabst.htm   (13464 words)

Molar Pregnancy Support Group Partial molar pregnancy--This occurs when the egg is fertilized by two sperm or an abnormal sperm containing two sets of chromosomes, therefore introducing three sets of chromosomes (69) at conception rather than just the needed two sets of chromosomes (46). The egg from the female is fertilized by a sperm by the male, thereby introducing one set of chromosomes (23) from each parent, introducing 46 chromosomes to the fertilized egg. Complete molar pregnancy--This occurs when either the sperm or the egg involved in fertilization is "empty" (no chromosomes present). www.angelfire.com /journal/molarpregnancy   (13464 words)

Molar pregnancy In most complete molar pregnancies, the fertilized egg contributes no maternal chromosomes and the chromosomes from the father's sperm are duplicated, so you end up with two copies of chromosomes from the father and none from the mother. In most partial molar pregnancies, the fertilized egg has the normal complement of chromosomes from the mother but double the chromosomes from the father, so there are 69 chromosomes instead of the normal 46. It doesn't necessarily mean signal a molar pregnancy, but your practitioner will likely order an ultrasound to find out what's causing it and may do a blood test to measure your levels of the hormone hCG. www.babycenter.com /refcap/pregnancy/pregcomplications/1363614.html   (13464 words)

Finland and the Tat-C Controversy On this basis, the assumption has been made that around 55% of Finnish Y Chromosomes, 47% of Lithuanian Y Chromosomes, 32% of Latvian Y-Chromosomes, 37% of Lithuanian Y-Chromosomes, and 5.7% of Norwegian Y-Chromosomes are 'Asiatic' in origin. A study by Jeffrey Lell et, al, titled The Dual Origin and Siberian Affinities of Native American Y Chromosomes, published in the American Journal, of Human Genetics, volume 70, pages 192-206, in 2002, asserted that the 'Tat-C' marker was 'Siberian' in origin: There's a very striking genetic frontier there, in spite of the fact that the two nations are neighbours with nothing much in the way of rivers or mountain ranges to prevent access either way, and they have even lived under the same rulers for centuries!" www.stormfront.org /whitehistory/finland.htm   (3164 words)

Scientists sequence human X chromosome The X chromosome, by contrast, is sized much closer to the other human chromosomes not involved in sex determination, which are collectively known as autosomes. Other sex chromosomes currently being sequenced at the GSC include the mouse and chimp Y chromosomes and the chicken sex chromosomes, which are different from other sex chromosomes and known as the Z and W chromosomes. The X chromosome genome sequence has already allowed researchers to isolate more than 40 genes involved in medical conditions, improving their ability to diagnose the disorders and potentially opening up new avenues for development of treatments. mednews.wustl.edu /news/page/normal/4966.html   (596 words)

EUKARYOTIC CHROMOSOME STRUCTURE 7 This indicates that polytene chromosome bands are composed of the same scaffolding ring-like structures and subunits as metaphase chromosomes and this is best shown when the gross structure of the bands is also well preserved. On EM inspection of metaphase chromosomes and interphase nuclei, after any of the various spreading and washing methods, and after 2 M salt extraction before or after DNase digestions, networks of ring-like structures were uncovered, in the residual (scaffolding) parts of the chromosomes. Looking at polytene chromosomes, spread according to Kalisch and Hägele (1981), indicated that all bands were composed of tight clusters of similar pore or ring-like structures shown here in Fig. www.lce.hut.fi /~engelhar/Doc/Dis-ResII.html   (596 words)

Variation in Chromosome Number Changes in chromosome number can occur by the addition of all or part of a chromosome (aneuploidy), the loss of an entire set of chromosomes (monoploidy) or the gain of one or more complete sets of chromosomes (euploidy). In addition, to variation in whole chromosome numbers, genetic stocks have been developed, especially in plants, where parts of chromosomes are retained. (Stocks containing these types of chromosomes are called monotelosomics or monotelos for short.) Another type of structure is the isochromosome which is a chromosome that contains the same genetic material on both arms. www.ndsu.nodak.edu /instruct/mcclean/plsc431/chromnumber/number1.htm   (339 words)

Human Genetics - Chromosomal Inheritance 2 The events of embryogenesis during the time both X chromosomes are functioning in the female must be critical, as well as those few regions of the X chromosome that are not inactivated. Which of the two X chromosomes gets turned off in each of the 100 cells is purely a random event except where one of the X chromosomes is abnormal (deletion, insertion, inversion, etc.) An abnormal X is always turned off. Inversions, non-Robertsonian translocations, and ring chromosomes all produce, or have the potential for producing, altered phenotypes. www.uic.edu /classes/bms/bms655/lesson10.html   (339 words)

Chromosome - Wikipedia, the free encyclopedia Chromosomes were first observed in plant cells by Swiss botanist Karl Wilhelm von Nägeli (1817-1891) in 1842, and independently, in Ascaris worms, by the Belgian scientist Edouard Van Beneden (1846-1910). Like many sexually reproducing species, humans have special gonosomes (sex chromosomes, in contrast to autosomes for body functions). In the chromosomes of eukaryotes, the uncondensed DNA exists in a quasi-ordered structure inside the nucleus, where it wraps around histones (structural proteins, Fig. en.wikipedia.org /wiki/Chromosome   (1702 words)

Genetic Algorithm Graphing Applet This is because as the population improves, it becomes nearly impossible for chromosomes with poor fitness to advance to the next generation (we also observe that with tournament selection, there is no way for the (unique) worst chromosome in the population to advance). The program accepts parameters for the number of generations (default 100), the size of the population (default 100), the size of the chromosomes (default 20), the probability of crossover for every two chromosomes selected for reproduction (default 0.7), and the probability for a bit to randomly mutate (default 0.001). Tournament selection chooses a chromosome by selecting two chromosomes from the population at random, and then taking the one with the higher fitness. www.cs.hmc.edu /~phenry/final/GeneticApplet.html   (930 words)

Genome Glossary For the human genome, the lowest-resolution physical map is the banding patterns on the 24 different chromosomes; the highest-resolution map is the complete nucleotide sequence of the chromosomes. The diploid human genome consists of a total of 46 chromosomes: 22 pairs of autosomes, and 1 pair of sex chromosomes (the X and Y chromosomes). Eukaryotic genomes consist of a number of chromosomes whose DNA is associated with different kinds of proteins. www.ornl.gov /sci/techresources/Human_Genome/glossary/glossary.shtml   (930 words)

Edwards' syndrome Chromosomes are numbered 1-22, and the 23rd pair is composed of the sex chromosomes, X and Y. A person inherits one set of 23 chromosomes from each parent. Chromosomes are separated from cells, stained, and arranged in order from largest to smallest so that their number and structure can be studied under a microscope. Occasionally, a genetic error occurs during egg or sperm cell formation. www.healthatoz.com /healthatoz/Atoz/ency/edwards_syndrome.jsp   (930 words)

Creation Essay 32 This is what we have termed "classical genetics." The new "molecular genetics" which is a part of molecular biology is a study of the chromosomes and the genes in the chromosomes at the level of their molecular structure and the actual arrangement of the atoms in the genes. Geneticists study the chromosomes of organisms, the location of particular genes on the chromosomes, and changes (mutations) and rearrangements in the chromosomes and their genes which are transmitted by inheritance to succeeding generations. Genetics relates the chromosomes and their genes to the inherited characteristics of organisms. www.parentcompany.com /creation_essays/essay32.htm   (1365 words)

Chapter 8 Supplement Polytene Chromosomes: the bundles of multiple replicas of DNA sets produced by repeated passes through the S-phase without mitosis; remain co-aligned along the length of the chromatid strands, forming giant chromosomes; often the homologus chromosomes are paired in somatic cells; cells with polytene chromosomes cannot undergo mitosis. These may be arranged from a photograph of the "spread" chromosomes in metaphase, or late prophase, in an orderly way to form a karyotype. Nucleolar organizers: secondary constrictions of the chromosomes where the nucleoli are found in interphase; they have highly specific positions on the DNA and contain genes for ribosomal RNA; there positions are used as landmarks for cytogenetic studies. www.utexas.edu /courses/zoo325/chap8.htm   (1365 words)

American Journal of Botany, 9, 7, July, 1922 The univalent chromosomes are arranged end to end, or telosynaptically, in these loops, the places where they join being marked by constrictions. The chromosomes in this plant are arranged telosynaptically, and form a univalent spireme during prophase of the heterotypic mitosis. The bivalent chromosomes emerge in a definite way from the second contraction, and are arranged in such a manner that they form one closed circle, consisting of four univalent chromosomes, and five rings composed each of two chromosomes, all of which are linked together at first according to a definite scheme. www.botany.org /ajb/00029122_di001204.html   (1365 words)

Variation in Chromosome Number Euploidy - an entire set of chromosomes is duplicated once or several times Changes in chromosome number can occur by the addition of all or part of a chromosome (aneuploidy), the loss of an entire set of chromosomes (monoploidy) or the gain of one or more complete sets of chromosomes (euploidy). Monoploidy - the loss of an entire set of chromosomes www.ndsu.nodak.edu /instruct/mcclean/plsc431/chromnumber/number1.htm   (1365 words)

Aneuploidy and Deletions Euploid human females have 46 chromosomes (44 autosomes and two X chromosomes), and euploid bulls have 60 chromosomes (58 autosomes plus an X and a Y chromosome). Aneuploidy is the condition of having less than or more than the normal diploid number of chromosomes, and is the most frequently observed type of cytogenetic abnormality. Euploidy is the condition of having a normal number of structurally normal chromosomes. arbl.cvmbs.colostate.edu /hbooks/genetics/medgen/chromo/aneuploidy.html   (1365 words)

DEVELOPMENTAL BIOLOGY: ON INACTIVATION OF THE X CHROMOSOME Later on, in the embryonic tissues, X inactivation is random with respect to the parental origin of the X chromosomes[4]. This meiotic inactivation uniquely affects the sex chromosomes and may be associated with the inability of the X and Y chromosomes to pair during male meiosis[5]. Mammals have evolved a unique form of dosage compensation, called X-chromosome inactivation, in which one of the two X chromosomes in female cells is silenced epigenetically[1] -- that is, by factors such as chemical modification of the DNA, or of the histone proteins that package DNA into chromosomes, often involving non-coding RNAs. scienceweek.com /2005/sw051230-4.htm   (2233 words)

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