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Genes, Ch 4, 5

McCance Notes

QuestionAnswer
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