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Genes, Ch 4, 5
McCance Notes
| Question | Answer |
|---|---|
| chromatin | precursor to chromosomes, contains genes; DNA |
| DNA | deoxyribonucleic acid, make up genes, blueprint of proteins; influence structure & function |
| Recombinant DNA | combining DNA of two or more different organisms: bacterial plasmids cleaved at restrictive sites by endonucleases--bacteria can grow human proteins, ex: insulin, HGH, interferon |
| mRNA | messenger ribonucleic acid; coder for genes. transciption-copy of DNA |
| cDNA | complementary DNA made from extracted mRNA (c/reverse transcriptase) during recombinant DNA technique for gene manufacturing |
| PCR | polymerase chain reaction; rapid way of making millions of copies of DNA by temperature cycling in a couple of hrs. vs 1 week using cloning techniques (forensics use this) |
| somatic cell therapy | gene therapy, inserting normal genes into person with genetic dx.;hemophilia, CF, familial hypercholesterolemia, some ca |
| gene cell therapy | not presently happening, but is the process of inserting genes into embryo-alter future descentants as well, very controversial |
| gene components | deoxyribose (sugar molecule), phosphate molecule; 4 nitrogeneous bases-A, C, T, G, adenine, guanine, cytosine, thymine |
| pyrimidines | cytosine, thymine, (C, T); single carbon nitrogen ring. one pair of the two types of rungs of the DNA ladder-always pair together |
| purines | adenine, guanine (A, G); double carbon-nitrogen ring. one pair of the two types of rungs of DNA ladder-always pair together |
| codons | nucleotide sequences of DNA- 64 different combination, 61 that can make 20 amino acids for protein. (3 terminal codons).Redudent |
| nucleotide | DNA subunit, 1 deoxyribose, 1 phosphate, 1 base (C,T,A,G) |
| DNA polymerase | enzyme adds bases together during replication and proofread and corrects pairing. C-T!!, A-G!! |
| mutation | alteration in genetic material. 1)base pair substitution-can be silent if doesn't affect amino acid. 2)frameshift mutation- insertion, deletion. mutagens: radiation, chemicals; spontaneous |
| RNA | ribonucleic acid. transcripes and translates DNA for protein synthesis. mRNA, tRNA, rRNA |
| tRNA | transfer RNA-necessary for translation of mRNA and forms polypeptides (several polypeptides make up a complete protein molecule) |
| DNA replication sequence | DNA-mRNA(RNA polymerase)-tRNA-ribosome/rRNA = polypeptide |
| ribosome | actual site of protein synthesis |
| dipoid cells | chromosomes appear in pairs. (23 pairs or 46 chromosomes in the nucleus of each somatic cell) |
| haploid cells | one member of each chromosome pair-23 chromosomes, gamate cells-sperm and egg cells. |
| euploid cells | multiple of the normal number of chromosomes |
| polyploid | euploid cells has more than the diploid number of chromosomes; normal-liver, bronchial, epithelial tissue (triploidy-three copies of ALL chromosomes;tetra-10% of miscarriages or stillborn) |
| aneuploid cell | somatic cell does not contain multiple of 23 chromosomes; 3 copies of ONE chromosome-trisomy-can survive. one copy of one chromosome-monosomy-lethal. usually from nondisjunction. |
| Downs syndrome | trisomy chromosome 21, often caused by nondisjunction of mother's egg. > with age bc egg is older. |
| nondisjunction | error in which homologous chromosomes fail to separate normally during meiosis, or mitosis, resulting in extra or no copy of chromosome |
| mutation hot spot | certain areas of chromosome have particular high mutation rates. sequences of cystine following guanine base-responsible for large % of disease mutations |
| parial trisomy | only part of an extra chromosome is present-less severe consequences. |
| chromosomal mosaic | trisomy is only in part of the cells; two different cell lines-early nondisjunction in one but not all embryonic cells. (1% Downs-mosaic-less sever sx.) |
| Turner syndrome | XXX, 45,X. sterile, short, 1/2 webbing of neck, coarctation of aorta, edema of feet of NB, cubitus valgus, sparse body hair, spatial and math reasoning impairment-but not retarded. usually loss of paternal X chromosome |
| Klinefelter syndrome | 47,XXXY karotype, male appearance, sterile, gynecomastia, sparce body hair, small teste, high pitch voice, elevated stature, mental retardation. > sx c more X chromosomes |
| 45,X | most common single chromosome abnormality, Turner syndrome. 15-20% spontaneous abortion. |
| sex chromosome aneuploidy | Turner, Klinefelter, 47,XYY |
| clastogen | extent of chromosome breakage is increased with presence of clastogen such as ionizing radiation, some viral infections, certain chemicals |
| deletion | broken chromosome with loss of DNA, ex: cri du chat syndrome |
| cri du chat syndrome | cry of cat sound when baby cries, microcephaly, LBW, severe mental retartdation, heart defects, facial anomalies, deletion of short arm of chromosome 5 |
| duplication | extra chromosome material-less serious consequence than deletion |
| inversion | inverted when broken chromosome put back together. affects seen in offspring's children-having deletion or duplication |
| translocations | interchange of genetic material between nonhomologous chromosomes; Robertsonian, reciprocal, offspring children can develop duplication/deletion such as Downs |
| fragile sites | Fragile X syndrome, 2nd most common cause of mental retardation. carrier of fragile X gene and pass it on to offspring. deletion/duplication defect |
| alleles | different forms that genes can take at a certain locus on the chromosome |
| genotype | composition of genes at a given locus |
| phenotype | outward appearance of individual r/t gene and environment |
| heterozygote | loci affect of one allele may mask another when they are together,Aa dominant trait-observed; recessive trait-hidden |
| homozygote | two recessive traits together for expression, aa, (late onset, variable expression, incomplete penetrance) |
| codominance ?? | heterozygote is distiguishable from homozygotes; ABO |
| pedigree chart | summarizes family relationships and shows which members are affted by a genetic disease, anaylysis of mode of transmission, female -circle; male-square |
| penetrance | having genotype without expressing phenotype-still pass gene on to next generation |
| obligated carrier | parents have disease, children have disease but person does not-, penetrance of gene subtracted from % of obligated carriers |
| Type 1 neurofibromatosis | autosomal dominant, with variable expressivity. neurofibromatosis-chromosome 17. parent mild expression, passes on severe expression. mild-cafe au lait spots to malignant neurofibromas, scoliosis, seizures, htn, gliomas, learning disabilities |
| expressivity | extent of variations in phenotypes associated with a particular genotype. complete penetrance with variable expressivity and severity of disease |
| hemophilia A | variable expression of gene based on type of mutation/locus. base-substitute of single amino acid: mild clotting disorder vs. base sub. of codon-cause severe form. (x-linked recessive gene; p. 154 ) |
| cystic fibrosis | autosomal recessive gene (homozygous, aa, to be expressed, long arm of chromosome 7, defect in Cl-transport pump, causes salt imbalance, thick secretions, obstructed pancreas, malabsorption, lungs clogged. |
| sex-linked | genetic disorders assoc with X/Y chromosomes. Usually X b/c Y chromosome only has a few dozen genes. males have > x-linked diseases b/c they only have one X chromosome, but females need homozygous for X-linked recessive traits. (ex: hemophilia A) |
| Duchenne muscular dystrophy | most common & severe form of X-linked recessive disorders; no dystrophin, causes muscle degeneration, unable to walk by 10, die of heart/resp prob by 20. ex: frameshift deletion of the DMD gene |
| incidence | number of new cases of a disease reported during a specific time period |
| prevelance | proportion of population affected by disease at a given point in time. (incidence and survival length affect prevelance.) |
Created by:
Sniffen group
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