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All Articles Within Chromosomes and Cytogenetics (34)

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Chromosome Analysis (10)

• Chromosome Mapping: Idiograms
  How do scientists find their way around a chromosome? With chromosome maps called idiograms, researchers can pinpoint the locations of genes and locate abnormal gene forms.
• Fluorescence In Situ Hybridization (FISH)
  Cytogeneticists can now go "FISH-ing" for chromosomal abnormalities, which are deletions and duplications that can cause disease. How exactly does FISH work?
• Chromosome Territories: The Arrangement of Chromosomes in the Nucleus
  Chromosomes occupy specific regions of a nucleus, called "chromosome territories." These subdomains might be doing much more than just keeping everything organized.
• Human Chromosome Translocations and Cancer
  Translocations generate novel chromosomes, but are often linked to disorders like infertility and cancer. How do these new chromosomes generate problems, and how are they detected?
• Karyotyping for Chromosomal Abnormalities
  Each chromosome pair viewed in a karyotype appears to have its own distinct “bar code” of bands. What changes do scientists look for in a karyotype when diagnosing diseases and disorders?
• Cytogenetic Methods and Disease: Flow Cytometry, CGH and FISH
  Some diseases involve regions of chromosomes that have been flipped or damaged. Find out what techniques scientists are using to dissect these chromosomes at the molecular level.
• Prenatal Screen Detects Fetal Abnormalities
  How can prospective parents ensure that they will have a healthy baby? Prenatal testing can provide parents with information about their child’s genetic identity.
• Microarray-based Comparative Genomic Hybridization (aCGH)
  Move over karyotypes—genetic disorder detection has vastly improved. Researchers are now using array CGH (aCGH), to quickly scan through an entire genome for imbalances.
• Diagnosing Down Syndrome, Cystic Fibrosis, Tay-Sachs Disease, and Other Genetic Disorders
  A genetic screen can potentially diagnose more than 1,200 genetic disorders and chromosomal abnormalities. If you were a medical geneticist, how would you pick the best test for your patient?
• Synteny: Inferring Ancestral Genomes
  Fragments of chromosomes from extinct species can be detected in many of their living descendants. How do investigators piece these fragments together to deduce our evolutionary history?

Chromosome Number (4)

• Chromosomal Abnormalities: Aneuploidies
  Aneuploidies disturb the delicate balance of gene products in cells by changing the chromosome number. What are the causes and phenotypic consequences of these meiosis mishaps?
• Polyploidy
  Polyploids are common among plants, as well as among certain groups of fish and amphibians. How does this interesting condition crop up, and what advantages and disadvantages does it impart?
• Human Chromosome Number
  Cytologists had been studying chromosome behavior since the late 19th century. Why did it take until 1956 to figure out the correct human chromosome number, thanks to Joe Hin Tjio and Albert Levan?
• Trisomy 21 Causes Down Syndrome
  A century after Down syndrome was first described, scientists discovered that the root cause of this disorder is a condition called trisomy 21. What strides in research have been made since then?

Chromosome Structure (6)

• Chromosome Mapping: Idiograms
  How do scientists find their way around a chromosome? With chromosome maps called idiograms, researchers can pinpoint the locations of genes and locate abnormal gene forms.
• DNA Packaging: Nucleosomes and Chromatin
  Each of us has enough DNA to reach from here to the sun and back, more than 300 times. How is all of that DNA packaged so tightly into chromosomes and squeezed into a tiny nucleus?
• Telomeres of Human Chromosomes
  In the 1930s, Muller was surprised to note that telomeres were strangely resistant to mutagenic X-rays. Why are the unique properties of these chromosomal "end caps" so important?
• Chromosome Territories: The Arrangement of Chromosomes in the Nucleus
  Chromosomes occupy specific regions of a nucleus, called "chromosome territories." These subdomains might be doing much more than just keeping everything organized.
• Chromosome Segregation in Mitosis: The Role of Centromeres
  Without centromeres, cells cannot divide properly and the overall process of mitosis fails. Why are these small chromosomal regions so essential to such a major cellular process?
• Genome Packaging in Prokaryotes: the Circular Chromosome of E. coli
  How do bacteria, lacking a nucleus, organize and pack their genome into the cell? Supercoiling enables this but forces a different kind of transcription and translation in prokaryotes.

Mutations and Alterations in Chromosomes (14)

• Chromosomal Abnormalities: Aneuploidies
  Aneuploidies disturb the delicate balance of gene products in cells by changing the chromosome number. What are the causes and phenotypic consequences of these meiosis mishaps?
• DNA Deletion and Duplication and the Associated Genetic Disorders
  Deletions and duplications of single-base pairs typically arise during homologous recombination and cause diseases. But what happens when a mutation occurs over multiple genes?
• Chromosomes and Disease
  This learning path will help you understand the ways that chromosomes are linked to some human diseases and will discuss some of the techniques involved in studying chromosomes.
• Human Chromosome Number
  Cytologists had been studying chromosome behavior since the late 19th century. Why did it take until 1956 to figure out the correct human chromosome number, thanks to Joe Hin Tjio and Albert Levan?
• Chromosome Abnormalities and Cancer Cytogenetics
  Thousands of chromosomal aberrations have been discovered in different types of cancer. But how do these various changes all hijack normal cellular processes to promote cancer?
• Human Chromosome Translocations and Cancer
  Translocations generate novel chromosomes, but are often linked to disorders like infertility and cancer. How do these new chromosomes generate problems, and how are they detected?
• X Chromosome: X Inactivation
  Females (XX) carry twice as many X-linked genes on their sex chromosomes as males (XY). How do cells control gene expression to manage this potentially lethal dosage problem?
• Trisomy 21 Causes Down Syndrome
  A century after Down syndrome was first described, scientists discovered that the root cause of this disorder is a condition called trisomy 21. What strides in research have been made since then?
• Karyotyping for Chromosomal Abnormalities
  Each chromosome pair viewed in a karyotype appears to have its own distinct “bar code” of bands. What changes do scientists look for in a karyotype when diagnosing diseases and disorders?
• Cytogenetic Methods and Disease: Flow Cytometry, CGH and FISH
  Some diseases involve regions of chromosomes that have been flipped or damaged. Find out what techniques scientists are using to dissect these chromosomes at the molecular level.
• Prenatal Screen Detects Fetal Abnormalities
  How can prospective parents ensure that they will have a healthy baby? Prenatal testing can provide parents with information about their child’s genetic identity.
• Genetic Recombination
  How does DNA recombination work? It occurs frequently in many different cell types, and it has important implications for genomic integrity, evolution, and human disease.
• Synteny: Inferring Ancestral Genomes
  Fragments of chromosomes from extinct species can be detected in many of their living descendants. How do investigators piece these fragments together to deduce our evolutionary history?
• Copy Number Variation and Human Disease
  Analysis of individual human genomes has revealed an unexpected amount of variability in human populations. Copy number variation (CNV) has recently been identified as a major cause of structural variation in the genome, involving both duplications and deletions of sequences that typically range in length from 1,000 base pairs to 5 megabases, the cytogenetic level of resolution. Evidence is accumulating that CNVs play important roles in human disease.

Sex Chromosomes (5)

• Genetic Mechanisms of Sex Determination
  In 335 B.C.E., Aristotle proposed that the heat of the male partner during intercourse determined sex. At least in the case of reptiles, Aristotle was on to something. What about in other animals?
• Sex Chromosomes in Mammals: X Inactivation
  Transcriptionally “silent” Barr bodies maintain gene equality in male (XY) and female (XX) cells. How are these unique sex chromosomes formed?
• Sex determination in honeybees
  In humans, sex is determined by the presence or absence of X or Y sex chromosomes. In honeybees, however, evolution has resulted in a very different and unique sex determination system.
• X Chromosome: X Inactivation
  Females (XX) carry twice as many X-linked genes on their sex chromosomes as males (XY). How do cells control gene expression to manage this potentially lethal dosage problem?
• Sex Chromosomes and Sex Determination
  In humans and many other animals, specific chromosomes determine sex. But how did researchers discover these so-called sex chromosomes?

Chromosome Theory and Cell Division (5)

• Chromosome Theory and the Castle and Morgan Debate
  Scientific debates can be as passionate and high-profile as political ones. Learn about an epic battle waged between the Castle and Morgan laboratories over the organization of genes.
• Developing the Chromosome Theory
  Scientists were able to identify chromosomes under the microscope as early as the 19th century. But what did it take for them to figure out how important chromosomes really are?
• Chromosome Segregation in Mitosis: The Role of Centromeres
  Without centromeres, cells cannot divide properly and the overall process of mitosis fails. Why are these small chromosomal regions so essential to such a major cellular process?
• Mitosis and Cell Division
  The 5 phases of mitosis and cell division tightly coordinate the movements of hundreds of proteins. Could fully unraveling this complex dance of chromosomes help biologists cure cancer?
• Meiosis, Genetic Recombination, and Sexual Reproduction
  How is the same process responsible for genetic recombination and diversity also the cause of aneuploidy? Understanding the steps of meiosis is essential to learning how errors occur.