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Download A human has 46 chromosomes normally, 44 of autosomal
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A human has 46 chromosomes normally, 44 of autosomal chromosomes and 2 of sex chromosomes (male→XY, female→XX) Generally an autosomal cell is diploid (2n=46), whereas a sex cell (sperm or egg) is haploid (n=23). ○Human inheritance types Mendelian types autosomal dominant recessive incomplete dominant codominant traits Non-mendelian types sex-linked inheritance multifactorail or polygenic inheritance <Mendelian types> Mendelian types obey the Mendelian lows. ①Low of uniformity ②Low of segregation ③Low of independent assortment 1. Autosomal dominant AA → disease Aa → disease ・only homozygous recessive is non-affected (healthy). aa → healthy Examples of autosomal dominant diseases ○Huntington disease ・mutation of gene encodes huntingtin protein. ・symptoms; neurodegenerative disorder (involuntary movements, personality changes, dementia) ○Hypercholesterolemia ・mutation of LDL receptor ○Osteogenesis imperfecta ・mutation of collagen ・symptoms; fragile bone, deafness, blue sclera 2. Autosomal recessive AA → healthy ・ only homozygous recessive is affected (disease) Aa → healthy ・ most common way of inheritance aa → disease Examples of autosomal recessive diseases ○Albinism ・no pigment of eye, hair, skin. ・mutation of tyrosinase enzyme gene (production of melanin is insufficient) ○Sickle cell anemia ・mutation of amino acid sequence in hemoglobin (glutamate is altered to valine → tertiary structural formation is changed due to less solubility) ・heterozygous advantage is characteristic (recessive allele is resistant to malaria) ○Phenylketonuria ・mutation of phenylalanine hydroxylase enzyme (the enzyme which converts phenylalanine to tyrosine) ○Thalassemia ・mutation of production of one or more peptide chains of globin 3.Imcomplete dominant Heterozygote shows intermediate between the dominant phenotype and recessive phenotype. Example; the color of sweet peas Dominant allele [A]; Purple Recessive allele [a]; White Heterozygote Aa; Purple, white, light purple 4. Codominant One or more than one traits show dominance to one trait. Example; ABO blood group A and B are equally dominant to O <Non-Mendelian types> 1. Sex-linked inheritance ・the trait which is inherited to offspring is on the sex chromosome (mostly on the X chromosome) ・in female, 1 X chromosome is carried by her mother another is carried by her father. ・in male, X chromosome is carried by his mother Y chromosome is carried by his father. (1)X-linked dominant Female Male XAXA → disease XAXa → disease XaXa → healthy XAY → disease XaY → healthy Examples of X-linked dominant diseases ○Amelogenesis imperfecta ・abnormal formation of enamel ○Familial hypophosphatemic rickets ・decreased reabsorption of phosphate by renal tubule ○Fragile X syndrome ・mental disorder (2)X-linked recessive Female Male XAXA → healthy XAXa → healthy XaXa → disease XAY → healthy XaY → disease Examples of X-linked recessive diseases ○Color blindness ○Hemophilia ○Duchenne muscular dystrophy (weakening of muscles) ・The incidence of X-linked inherited disease is much greater in males than in females because; ・female has 2 X chromosomes. (especially in the case of X-linked recessive) ・Dosage compensation (especially in the case of X-linked dominant) →One X chromosome is inactivated randomly in early embryo and an inactivated X chromosome is seen as a Borr body near the cell membrane. (3)Y-linked inheritance ・Only male is affected (affected father transmits disease 100% to his son) 2. multifactoral or polygenic inheritance ・one phenotype is regulated or interacted by several genes and environmental factors (1)Gene interaction ①collaboration (cooperation) 2 genes work together to produce a new phenotype. Ex. walnut comb of chicken ②epistasis Ex. color of Labrador retriever (1allele gives color, another gives color precursor) ③additive effect (2)Polygenic inheritance Skin color, body height, etc. due to additive gene interaction, incomplete dominance and environmental factors, etc. ※Sex-influenced trait Ex. Baldness ・autosomal dominant in males, but autosomal recessive in females ○Chromosomal mutations or aberrations 1. Structural (1)Translocation ・a chromosome fragment breaks off and attaches to a non homologous chromosome ・in reciprocal translocation(most common type of translocation), 2 non homologous chromosome exchange parts. Example; ○Philadelphia chromosome・・・example of reciprocal translocation ○Translocational down syndrome・・・example of Robertsonian translocation ・have one chromosome 14, one combined 14/21 chromosome, and two normal copies of chromosome 21 ・the large arm of chromosome 21 has been translocated to the large arm of chromosome 14 ・all or part of the genetic material from chromosome 21 is thus present in triplicate (2)Deletion ・part of a chromosome is missing Example; ○Cri du chat syndrome ・part of the short arm of chromosome 5 is deleted ・symptoms; small head, moon face, cry sounds like a kitten mewing, mental retardation (3)Inversion (4)Insertion with translocation (5)Ring chromosome (6)Isochromosome (7)Duplication 2. Numerical (1)Polyploidy. ・the presence of multiple sets of chromosomes ・lethal in human (2)Aneuploidy ・the presence of a single extra chromosome(trisomy), or the absence of a chromosome(monosomy) ・result of nondisjunction(abnormal meiotic division in which chromosomes fail to separate) ①Monosomy ○Turner syndrome ・has only 1 X chromosome [XO] ・develops as a female, but internal and external genital structures are underdeveloped → sterile ・no Borr body ②Trisomy ・autosomal ○Down syndrome・・・trisomy of chromosome 21( abnormal physical and mental development) ○Edwards syndrome・・trisomy of chromosome 18 ○Patau syndrome・・・trisomy of chromosome 13 ・gonosomal ○Kleinefelter syndrome・・trisomy of X chromosome in male [XXY] has 1 Borr body ○Super male (XYY syndrome)・・trisomy of Y chromosome in male ○Super female (XXX or triple X syndrome)・・trisomy of X chromosome in female ○Viruses 1. Structure capsid (protein coat) + nucleic acid (DNA or RNA) 2. Bacteriophage・・host cell is bacteria life cycle ① lytic cycle (virulent bacteriophage) ・break down the DNA of host bacterium and bacterium itself as well ②lysogenic cycle (template bacteriophage) ・the genetic material of phage is inserted to the DNA of host bacterium and transmitted to next generations ・If there is a certain stimulus they turn into lytic cycle 3. Way of getting into host ・membrane fusion ・endocytosis 4. Major diseases caused by viruses ・AIDS: caused by HIV (example of retrovirus) ・Hepatitis B, C: caused by hepatitis viruses ・Herpes: caused by herpes virus ・Influenza: caused by influenza viruses ○Bacteria 1. Structure ・bacteria are prokaryote (circular DNA, no endomembrane system) ・cell wall: prevent from bursting in hypotonic condition, consists of sugars attached by peptides Gram positive bacteria・・thick cell wall Gram negative bacteria・・thin cell wall + outer membrane outside the cell wall ・capsule: jelly like substance ・pilus and flagellum ・plasmids 2. Reproduction (1)Asexual; genetically equal ①clones ②binary fission ③budding ④fragmentation (2)Sexual; genetically different ①transformation (from environment) ②transduction (occurred by bacteriophage) ③conjugation (occurred by transmitting or accepting plasmid) 3. endospore Not for reproduction but dormant form of bacteria Resistant to environmental changes 4. Metabolism (1)Autotrophs ・synthesize organic compounds from inorganic compounds by photosynthesis or chemosynthesis (2)Heterotrophs ・organic sources from other organisms ①Saprotrophs ; their carbon source is dead body of other organisms ②Parasites ; their carbon source is living organisms 5. Respiration (1)Aerobic (2)Anaerobic Facultative anaerobe: aerobic + anaerobic (tolerate Oxygen) Ex. yeast Obligate anaerobe: aerobic only (oxygen is poison for them) Ex. tetanus bacteria