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genes beyond mendel
biol 1210
| Question | Answer |
|---|---|
| chromosome theory of inheritance | genes are located on chromosomes at a particular locus (location) |
| define wild type & mutant & give example | wild type: most common phenotype for each trait, ex. red eyes in drosophila. Mutant: individuals w traits caused by mutations , ex. white eyes in drosophila. Mutants are often less represented in population |
| describe sex determination in humans | in humans & other mammals, F = XX, M = XY. Each ovum has X, each sperm has X or Y. All embryos initially develop both reproductive system, then SRY gene on Y chromosome codes for M sexual development. |
| briefly describe sex determination in other animals | Crickets: presence/absence of two X chrom, F = XX, M = X. Chickens: Z/W system, F = ZW, M = ZZ. Bees: whether individual is haploid or diploid, F = 2n, M = n |
| describe sex chromosomes in humans | determine the sex of individual. X chrom. is much bigger and has many more genes than the Y chrom. X & Y are nonhomologous: diff. genes, diff. size, diff. centromere position. Not all genes on the X chrom. relate to the sex of individual. |
| sex linkage | describes genes that are located on either sex chromosome. IN this class: only X-linked genes. |
| can M & F has recessive X-linked condition? Which sex is it more likely to be found? What about Y-linked? | yes, but more likely in M bc they only have 1 X chrom. Y-linked: no, only males have a Y chrom. |
| describe eye colour inheritance in drosophila | eye colour is X-linked in drosophila where dominant = red eyes and recessive = white eyes. Hence, only possibility for white-eye F is if the mom is white eye bc F have 2 X chrom. Remember if offspring is M, they must've got Y chrom. from dad (not his X) |
| colourblindness is a recessive X-linked trait. Why r M more likely to be colourblind than F in the human population? | M can only have 1 allele (they only have 1 X chrom.), so if recessive is possible it is likelier to be recessive than a F, who would have to be homozygous recessive (2 X chrom.) |
| describe X chrom. inactivation & why it happens | mammal F (XX) have twice the "dose" of X-linked genes than XY. during early embryonic development, 1 X chrom. in each female cell becomes almost completely inactivated to ensure M & F have the same "effective dose" (one active copy) of most X-linked genes |
| Barr Body | a compact object that an inactive X chrom. condenses into during mammal embryonic dev. Usually along inside of the nuclear envelope in a cell. |
| effects of X chrom. inactivation | once X chrom. is inactivated inside a cell, all mitotic descendants of that cell (copies) maintain the inactive X. Some cells activate 1 allele, some cells activate the other = F mammals r a mosaic: some express paternal X and some express maternal X |
| multiple allelism | when there r more than 2 alleles of a gene in a *population* - there may be dozens of alleles for a single gene |
| complete dominance | when an allele for a gene always masks the expression of another allele, these alleles show dominance. One allele is dominant and the other is recessive. The type of dominance Mendel's methods work for |
| codominance, its effect on heterozygotes & an example gene | when neither allele for a gene is dominant or recessive to the other. Heterozygotes show the phenotype of both alleles. Ex. ABO blood types in humans: IA & IA dominant to i, but IAIB produce both polysaccharides = AB blood type |
| incomplete dominance, its effect on heterozygotes & an example gene | when each allele for a gene does not completely mask the expression of the other. Heterozygous show an intermediate phenotype. Ex. flower colour in four-o'clocks - red RR x white rr = red RR, white rr, & pink Rr flowers |
| epistasis | A gene that modifies the phenotypic expression of other genes are said to show epistasis AKA 2+ genes working together to control a single trait. There r many diff. types of epistasis -> diff. modifications to typical 9:3:3:1 ratio |
| epistasis example | Dogs! (slides for visual) Black allele B complete dominant to brown allele b for coat colour, but gene E controls deposit of pigmentation in hair. If dog is homozygous recessive for E (ee), they will be blonde no matter what combination of B/b |
| quantitative characters | traits that vary in the population along a continuum |
| polygenic inheritance | an additive effect of 2+ genes on a single phenotype, usually indicated by quantitative variation. Ex. human skin colour |
| pleiotropy | one gene that influences several characters, ex. frizzled feathers, accelerated metabolism & delayed sexual maturation gene in chickens |
| environment & phenotype | sometimes the phenotype for a character depends on the environment & genotype, ex. Hydrangea may be pinker or bluer depending on the pH of the soil |
| why r humans bad subjects for genetic research? | generation time too long, parents produce few offspring, damn ethical issues disallows breeding experiments |
| pedigree | family tree that describes the interrelationships of parents & children across generations. 1 pedigree describes 1 specific characterstic. Allows inheritance patterns to be traced & tracked across generations, offspring to be predicted |
| carrier | a heterozygote that carries a recessive allele but is phenotypically normal |
| why are lethal diseases caused by dominant alleles rare in a population? | dominant expression of lethal disease would wipe them out and only homozygous recessive individuals that do not exhibit the disease would remain |
Created by:
AntBanana
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