Ch. 14 Mendel and the Gene Idea and 15 Chromosomal Basis of Inheritance
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OompaLumpiax3 on January 10, 2011
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52 terms
Terms | Definitions |
|---|---|
 Gregor Mendel | bred garden peas in order to study patterns of inheritance |
| particulate inheritance | type of inheritance where inherited characteristics are carried by discrete units known as genes |
| multiplication rule | for finding probability of two independent events happening, multiply chance of one happening by the chance that the other will happen |
| addition rule | for finding when more than one arrangement of events producing the specified outcome is possible, the probabilities for each outcome are added together |
| law of dominance | when 2 organisms, each homozygous for two opposing traits are crossed the offspring will be hybrid but will exhibit only the dominant trait |
| hybried | carrying 2 different alleles |
| law of segregation | states that during the formation of gametes, the 2 traits carried by each parent will separate |
| Monohybrid cross | Tt x Tt is this type of cross; cross of 2 organisms each hybrid for one trait |
| phenotype | appearance |
| genes | chemical makeup; types of genes |
| testcross | way to determine the genotype of an individual plant or animal showing the dominant trait; individual bring tested is crossed with homozygous dominant |
| law of independent assortment | applies when a cross is carried out between 2 individuals hybrid for 2 or more traits that are not on the same chromosome; the only factor that determines how these alleles segregate or assort is how the homologous pairs line up in metaphase of meiosis I |
| dihybrid cross | cross between individuals hybrid for 2 or more traits not on the same chromosome |
| linked genes | genes that are on the same chromosome; they won't assort independently |
| phenotype ratio of a dihybrid cross | 9:3:3:1 |
| incomplete dominance | dominance that's characterized by blending |
| codominance | dominance where both traits show because there is a single gene locus at which 2 allelic variants are possible, making it so the hybrid is NOT an intermediate of the 2 phenotypes; such as blood groups in humans (A, B, AB, O) |
| multiple alleles | more than 2 forms of allelic forms of a gene |
| pleiotropy | ability of a single gene to affect an organism in several or many ways; ex: in siamese cats, an allele responsible for coloration pattern is responsible for cross-eyed trait |
| epistasis | 2 separate genes control 1 trait, but 1 gene masks the expression of the other gene. the gene that masks the expression of the other gene is epistatic to the gene it masks. ex: melanin production has 2 alleles, C, which produces pigment, and c, which doesn't. if C isn't there to make melanin in the first place, even if a 2nd gene codes for melanin deposition, none will deposit because C isn't there. |
| polygenic | many characteristics like skin, hair color, and height come from a blending of several separate genes that vary along a continuum. |
| nurture vs. nature | interaction of genetic predisposition and the environment |
| sex-influenced trait | inheritance influenced by the sex of he individual carrying the traits; NOT sex-linked necessarily |
| # of linkage groups | is equal to the number of chromosomes; humans have 46 |
| autosomes | 44 chromosomes (1st 22 pairs) of the 46 |
| sex chromosomes | 2 chromosomes (23rd pair); X and Y OR X and X |
| sex-linked | traits carried on the X chromosome (Y is too short); females inherit 2 copies of these genes; males inherit 1 of these genes on their one X |
| recessive mutation | females only express this mutation if they have 2 mutated genes |
| carrier | carries one of each gene; males can't be this for sex-linked genes |
| dominant mutation | females can express this mutation if they have only 1 of this mutated gene |
| sex-linked examples | color blindness, hemophilia, muscular distrophy |
| crossover | the farther apart genes are on a chromosome, the more likely they'll be separated from each other during meiosis due to this event occuring at the chiasmata. makes it so AB x ab has 4 types of gametes(AB, Ab, aB, ab) instead of 2(AB, ab). is a major source of variation in sexually producing organisms |
| recombination | the result of crossing over; is a major source of variation in sexually producing organisms |
| map unit | distance on a chromosome that is the distance within which recombination occurs 1% of the time; rate of crossover doesn't give actual distance, but can give order of linked genes on the chromosome |
| linkage map | maps the differences between genes that are linked |
| pedigree | family tree that indicates the phenotype of one trait being studied for every member of the family; used to find how particular trait is inherited |
| x inactivation | early in the development of the embryo of a female mammal, one of the 2 chromosomes is inactivated in every somatic cell |
| genetic mosaic | produced by x inactivation in female mammals because sometimes one x is inactivated, sometimes the other is inactivated |
| barr body | the dark spot on the chromatin of every somatic cell in a female that is produced due to x inactivation |
| mutations | changes in the genome; there are chromosome types and gene types |
| genetic disorders | PKU, cystic fibrosis, tay-sachs huntington's disease, hemophilia, color blindness, duchenne muscular distrophy, sickle cell |
| chromosomal disorders | down syndrome, turner's syndrome, klinefelter's syndrome |
| deletion | when a fragment lacking a centromere is lost during cell division |
| inversion | when a chromosomal fragment reattaches to its original chromosome but in the reverse orientation |
| translocation | when a fragment of a chromosome becomes attached to a nonhomologous chromosome |
| polyploidy | when a cell or organism has extra sets of chromosomes |
| nondisjunction | error that sometimes happens during meiosis in which homologous chromosomes fail to separate as they shouuld |
| aneuploidy | any abnormal number of chromosomes |
| trisomy | chromosome present is in triplicate |
| triploid | an organism with extra set of chromosome is called this; 3n |
| polyploid | organism with extra sets of chromosomes |
| extranuclear genes | genes found in the mitochondria and chloroplasts; defects in the DNA here affects amount of ATP made and therefore the nervous system and muscles; always inherited from the mother |
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