Genetic process and alterations
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| The Cell cycle 2 phases Interphase Mitosis | Interphase: Normal cellular fxing
Mitosis: reproductive phase where 2 exact daughter cells produced
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| Interphase | 2 gap phases and synthesis phase
synthesis phase: where DNA is duplicated
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| Chromatin | uncoiled strands of DNA found in interphase
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| prep for mitosis starts with synthesis of DNA | replicated in synthesis phase then coiled around histones to form chromosomes. DNA is seen as chromosomes in Mitosis and meiosis
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| Centromere | joins two chromatids in center. Landmark to id one chromosome from another. location can chagne.
Chromatids: two duplicate strands of DNA to form chromosome. One will move to each daughter cell.
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| 4 phases of mitosis | prophase, metaphase, anaphase, telophase
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| Mitosis | cellular division. By first phase, all organelles and dna have been duplicated
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| prophase | nuclear env disappears, spindle fibers form and attach at chromosomes at centromeres
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| metaphase | chromosomes align at equatorial plate by centromeres. Easiest to id by microscope in this phase
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| anaphase | centromeres split to make separate chromatids and spindle fibers pull them to opp poles of ea cell
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| telophase | new nuclear membranes form around ea set of 46 chromatids now known as chromosomes. They uncoil to form chromotin and cytokinesis occurs producing 2 daughter cells ea with diploid number of 46 chromatin strands
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| Meiosis Haploid number | process done only in reproductive organs Haploid: produces gametes resulting in half of number of chromosomes
23 from mother, 23 from father
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| two cellular divisions | Meiosis I: reduction to haploid number
Meiosis II: divide like mitosis
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| phases of meiosis I phases of Meiosis II | I: pro, meta, ana, telo
II: meta, ana, telo
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| Meiosis I, reduction phase | sister chromosomes align (mom 1 with dad 1), crossing over happens, centromeres don't split just the pairs of chromosomes
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| What is crossing over | exchange of genetic material in sister chromosomes (mom1 and dad1)
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| By end of Meiosis I | two daughter cells produced with ea 23 chromosomes
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| Beginning of Meiosis II, mototic division | mitotic division results of 4 gametes ea w/ 23 chromosomes
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| gene | seq of DNA in chromosome that codes for specific protein or specific piece of genetic info
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| locus | position along chromosome that spec. gene is located
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| allele | diff forms of genes on same gene locus, eye or hair color
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| codon (triplet codon) | seq. of three nucleic acid bases that code for spec amino acid. 20 diff aa
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| karyotype | ordered display of chromosomes
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| DNA | genetic code
4 necleic acids: adenine, thymine, cytosine, guanine
replication by enzyme DNA polymerase
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| Altered genetic process | mutations
aneuploidy
altered chromosomal structure
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| mutation | probelms wtih genes not chromosomes, a segment of DNA that codes for a protein. Alteration in DNA seq and occurs during DNA replication in S phase before cell division. mutated DNA can be passed onto daughter cells or offspring in gametes
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| types of mutation: base pair or frameshift | base pair: replacement of single base pair by diff base pair
frameshift mutation: 1 or more base pairs inserted or deleted from DNA seq
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| Aneuploidy euploid | cells with multiples of normal number of chromosomes
haploid: 23 normal gamete
diploid: 46 normal somatic cell
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| polyploidy | abn cells contain multiples of euploid number (3x: triploid fetus: 69 or 4x: tetraplid fetus: 92)
Cannot survive
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| aneuploid | Can survive, do not contain euploid no.
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| polysomy trisomy monosomy | p: extra copies of chromosomes
t: 1 extra copy of chrom
m: only 1 copy of chrom, usually not survive EXCEPT with female inf. w/ monosomy of X chrom
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| Cause of aneuploidy | nondisjuntion: failure of separation of chromosomes during cellular reprod.
In meitotic div = gametes w/ abn no. of chrom(aneuploidy). Duplication is more survivable than deletion of genetic mat.
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| Mosaic Aneuploidy | special case where duplication or deletion of genetic matierial is not present in all cells
May be result of nondisjx during mitotic div after fertilization
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| example of autosomal aneuploidy | trisomy 21 (Down's syndrome), incr with maternal age
13 or 18 tend to die
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| features of trisomy 21` | low nasal bridge, low set ears, simian creases, epicanthal folds, protruding tongue, mental retardation, cardiac defects
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| Ex of Aneuploidy of sex chromosomes | Turner Syndrome: 45 chromosomes with monosomy of X (monosomy)
Klinefelter syndrome: extra X chrom, 47 XXY
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| Types of altered structure | deletions, duplications, inversions, translocations
Can happen in crossing over phase, not always.
Silent passed to children and loss of genetic material usually ends in death
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| Ex of chromosomal deletion | Cri du chat syndrome: deletion of short arm of chrom 5
high pitched cry, low birth wt, microcephaly, cardiac defects, severe mental retardation
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| Patterns that genetic inheritance and how alterations are transferred to offspring | not all inherited from parents
Homozygous: 2 alleles from mom/dad r identical(ex: both genes code for blue eyes, AA)
Heterozygous: 2 alleles not identical (Aa). One is dominant A, other recessive a. Can express dominant and carry recessive
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| genotype phenotype | g: actual genetic code in DNA
p: appearance or fx of individual. Can be influenced by env, not all predetermined by genetic structure
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| Ex of environmental influence of phenotype | phenylketonuria (PKU): inborn error of metabolism, lacks ability to metabolize phenylalanine. On long arm of chrom 12. Both recessive genes severe, but reduced with dietary restriction, so phenotypic expression is influenced
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| 4 main patterns of genetic inheritance | autosomal dominant
autosomal recessive
x-linked dominant
x-linked recessive
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| autosomal dominant transmission Dd affected x Dd affected Dd Affected x dd normal | Affected: DD, Dd, Dd
Normal: dd
Affected: Dd, Dd
Normal: dd, dd
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| Common autosomal dominant disorders | marfan syndrome, connective tissue weakness, fibrilin, risk for aorta tear
neurofibromatosis
Huntington's disease, Chorea, progressive dementia
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| Autosomal recessive transmission Dd x Dd | homo DD normal, hetero Dd carrier, Dd hetero carrier, dd homo affected
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| Ex. autosomal recessive inheritance | cystic fibrosis
Most common mutation: Delta 508 from deletion of triplet code for phenylalinine
phenylketoniuria
Tay-sachs disease: fat cells
sickle cell: hemoglobin molecules
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| Ex. X-linked dominant inheritance | hypophasphatemic rickets: defective protein in kidney, decr phosphate
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| X-Linked Recessive transmission XHXh x XHY XHXH x XhY XHXh x XhY | more common
affected: XhY, carrierXHXh, norm XHXH, XHY
aff: none, carrier XHXh, XHXh, norm XHY
aff: XhXh, XhY, carrier XHXh, norm XHY
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| Ex. X-linked Recessive inheritance | Duchenne Muscular Dystrophy
absent protein dystrophin which maintains structural integrity so get muscle wasting
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| Other X-linked Recessive disorders | Hemophilia A
Glucose-6-Phosphate Dehydrogenase deficiency (G6PD)
Agammaglobulinemia
color blindness
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| What is threshold of liability | no of defective alleles need to be present for disorder to be phenotypically expressed, may differ with gender
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| What is the human genome project | Determines location of many genes that code for disorders. It maps specific genes to spec disorders.
Gene therapy is experimental, not very successful.
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