Genetics

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hellosleepy
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167452
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Genetics
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2012-09-05 15:30:35
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  1. Karyotype
    Display of chromosomes ordered by their length 
  2. Haploid 
    • Having one copy of each chromosome 
    • N = 1
    • Human gametes 
  3. Diploid 
    • Having two copies of each chromosome 
    • N=2 
    • Human somatic cell 
  4. Aneuploid 
    Having one or more missing or extra chromosomes 
  5. Balanced chromosomal sbnormality 
    No net gain or loss of chromosomal material 
  6. Unbalanced chromosomal abnormality 
    Net gain or loss of genetic material 
  7. Uniparental disomy 
    A chromosome pair is derived solely from one parent in the diploid offspring 
  8. p and q arms of chromosome 
    p = short arm 

    q = long arm 
  9. Metacentric chromosome 
    Both arms are of equal length 
  10. Submetacentric chromosome 
    One arm is a bit shorter than the other arm 
  11. Acrocentric chromosome 
    One arm is much shorter than the other arm 
  12. Autosome 
    Any somatic chromosomes
  13. Sex chromosomes 
    Contrast with autosomes 

    In humans, X and Y are the sex chromosomes 
  14. Euchromatin 
    decondensed, active form of a chromosomal region 
  15. Heterochromatin 
    Condensed, inactive form of a chromosomal region 

    Facultative heterochromatin can become decondensed but constitutive is always condensed 
  16. Chromosome banding 
    Staining of bands of chromosome segments 

    Allows for the precise identification of individual chromosomes or parts of chromosomes 
  17. Nondisjunction 
    The failure of the paired chromosomes to segregate properly during meiosis or mitosis 

    Results in daughter cells with an abnormal number of chromosomes 
  18. Reciprocal translocation 
    Segments of two different chromosomes have been exchanged 
  19. Robertsonian translocation 
    Joining of two acrocentric chromosomes at the centromeres with loss of their short arms to form a single abnormal chromosome 
  20. Inversion 
    A segment of the chromosome is flipped around the and the genetic material is inverted 
  21. Ring chromosome
    Usually occurs when a chromosome breaks in two places and the ends of the chromosome arms fuse together to form a circular structure
  22. Origin of replication 
    Site on DNA molecule where replication starts
  23. Leading strand 
    The strand of DNA double helix that is copied in a continuous fashion 
  24. Lagging strand 
    The strand of the DNA helix that is copied in a discontinuous fashion 
  25. Topoisomerases 
    Class of enzymes that alter the supercoiling of double-stranded DNA 
  26. Helicases
    Enzyme that separates the strands of the DNA double helix 
  27. Okazaki fragments 
    Short segment of RNA-primed DNA that is synthesized on the lagging strand during replication 
  28. Antimetabolites 
    A drug or substance that is an antagonist to or resembles a normal metabolite and thus interferes with its function, usually by competing for its receptors or enzymes. 

    Antimetabolites used as anticancer agents include 5-fluorouracil (5-FU)
  29. Telomerase
    Enzyme consisting of RNA and protein components that maintains the ends of chromosomes by adding specific repeat sequences. 
  30. Polymerase slippage 
    DNA polymerase can lose its place in a repetitive sequence tract, and either leaves out or add an inappropriate number of repeat units.
  31. Base Excision Repair (BER)
    DNA repair process that involves the excision and replacement of a normal base 
  32. Nucleotide excision repair (NER)
    DNA repair process involving the excision and resynthesis of a polynucleotide region 
  33. Homologous recombination
    In the context of DNA repair, a process involving the recombination between homologous double-stranded DNA molecules.
  34. Nucleoside 
    Base + sugar 
  35. Nucleotide
    Base + Sugar + Phosphate
  36. Allele
    One of the alternative versions of a gene or DNA sequence at a given locus.
  37. Autosomal dominant
    • A pattern of inheritance in which an affected individual has one copy of a mutant gene and one normal gene on a pair of autosomal chromosomes 
    • (example: Huntington disease). 
  38. Autosomal recessive
    A pattern of inheritance in which an affected individual has two copies of the mutant gene (example: cystic fibrosis). 
  39. Codominant:
    If both alleles of a pair are expressed in the heterozygous state, then the alleles (and/or traits determined by them) are codominant. 
  40. Compound heterozygote:
    An individual or genotype with two different mutant alleles at the same locus.
  41. Consanguineous
    Related by descent from a common ancestor.
  42. Expressivity
    The extent to which a genetic defect is expressed. If there is variable expressivity, the trait may vary in expression from mild to severe but is never completely unexpressed in individuals who have the corresponding genotype. Contrast this concept with that of penetrance. 
  43. Founder effect
    A high frequency of a mutant allele in a population founded by a small  ancestral group when one or more of the founders was a carrier of the mutant allele.
  44. Genetic anticipation:
    • The progressively earlier onset and increased severity of certain diseases in successive generations of a family. Anticipation is caused by expansion of the  
    • number of unstable repeats within the gene responsible for the disease.  
  45. Genotype:
    • The genetic constitution f an individual, as distinguished from the phenotype.  
    • More specifically, the alleles present at one locus. 
  46. Heterozygous: 
    An individual or genotype with two different alleles at a given locus on a  pair of homologous chromosomes. 
  47. Homozygous
    An individual or genotype with identical alleles at a given locus on a pair of  homologous chromosomes. 
  48. Locus
    The position occupied by a gene on a chromosome. Different forms of the gene (alleles) may occupy the locus.
  49. Mutation:
    Any permanent heritable change in the sequence of genomic DNA. 
  50. Penetrance:
    The fraction of individuals with a genotype known to cause a disease who have any signs or symptoms of the disease. Contrast with expressivity. 
  51. Phenotype
    • The observed biochemical, physiological, and morphological characteristics  of an individual, as determined by his or her genotype and the environment in which it is  expressed. Also, in a more limited sense, the abnormalities resulting from a particular  
    • mutant gene. 
  52. Polygenic inheritance
    • Inheritance determined by many genes at different loci, with  
    • small additive effects; not to be confused with multifactorial inheritance, in which  environmental as well as genetic factors may be involved. 
  53. Proband
    The affected family member through whom the family is ascertained. 
  54. Random (disassortative) mating:
    • Selection of a mate without regard to the genotype of  
    • the mate. In a randomly mating population, the frequencies of the various matings  between individuals with particular genotypes are determined solely by the frequencies of  
    • the alleles concerned. 
  55. X-linked dominant:
    • Genetic inheritance by which a dominant gene is carried on the X  chromosome. A gene responsible for a genetic disorder is located on the X chromosome,  
    • and only one copy of the allele is sufficient to cause the disorder when inherited from a  parent who has the disorder.
  56. X-linked recessive
    • Genetic inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed (1) in males (necessarily hemizygous for the gene mutation because they have only one X chromosome) (2) in  
    • females (homozygous for the gene mutation: They have a copy of the gene mutation on each of their two X chromosomes).
  57. Shotgun sequencing 
    DNA sequence is shredded into random segments and the small fragments are then individually sequenced 

    The sequences of these fragments are then used to determine the sequence of the original DNA sample 
  58. Hierarchical shotgun sequencing approach 
    Large, overlapping DNA fragments of a known location in the genome are shredded and sequenced. 

    The sequences of these large fragments are then used to determine the sequence of the human genome 
  59. Whole-genome shotgun sequencing 
    Genome is shredded into small fragments and then sequenced to determine the sequence of the entire genome 
  60. Exome 
    The complete exon conent of an individual 
  61. Interspersed repeats 
    A class of specific repeat sequences in the human genome 

    Consit of LINE, SINE, and retro-virus like elements as well as DNA transposon fossils 
  62. LINEs
    Long interspersed nuclear elements 

    • a specific type of interspersed repeat element 
    • that encode the proteins necessary for their own replication
  63. SINEs 
    Short interspersed nuclear elements are

    • a specific type of interspersed repeat element 
    • that do not encode the proteins necessary for their own replication.
  64. Retrovirus like elements 
    Specific type of interspersed repeat element that may or may not encode the proteins necessary for their own replication
  65. DNA transposon fossils
    Specific type of interspersed repeat element that may or may not encode the proteins necessary for their own replication.
  66. Segmental duplications
    Sequences >1-kb in length that share 90-98% identity. A segmental duplication can contain interspersed repeat sequences.
  67. de novo mutations
    a sequence change that is present for the first time in one family member as a result of a mutation in a germ cell of one of the parents or in the fertilized egg
  68. Copy number variants
    sequence that is at least one kilobase in length and polymorphic. This definition may vary slightly depending on the source. 
  69. Single nucleotide polymorphism
    A polymorphism in DNA sequence consisting of variation in a single base. 
  70. Haplotype
    • A set of DNA variations, or polymorphisms that tend to be inherited together. A haplotype can refer to a combination of alleles or to a set of single nucleotide polymorphisms 
    • (SNPs) found on the same chromosome. 
  71. Genome-wide association study (GWAS)
    • a case-control study in which genetic variation, 
    • often measured as SNP genotypes, is compared between people with a particular trait and unaffected individuals. 
  72. Multifactorial Inheritance
    The type of non-Mendelian inheritance shown by traits that are determined by a combination of multiple factors, genetic, and environmental. 

    It is also termed complex inheritance. In principle, multifactorial inheritance can be polygenic (involving many genes at different loci), but it always has to be influence by the environment.
  73. Linkage
    Genes on the same chromosome are linked if they are transmitted together in meiosis more frequently than by chance
  74. Linkage Disequilibrium
    The nonrandom association between two or more alleles such that certain combinations of alleles are more likely to occur together on a chromosome than other combinations of alleles 
  75. Polygenic
    Inheritance determined by many genes at different loci, with small additive effects. It is distinct from multifactorial inheritance in that environmental factors are not involved.

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