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Genetics_CH3
Independent Assortment of Genes
| Question | Answer |
|---|---|
| Green Revolution | partly due to improved agriculture practice, but also due to the development of superior crop genotypes by plant geneticists |
| independent assortment | the alleles of two heterozygous gene pairs are said to act independently during meiosis |
| monohybrid | a heterozygote for a single gene |
| dihybrid | a double heterozygote |
| dihybrid crosses | crossing two genotypes (Mendel started this, and he developed an important principle of heredity based on his findings) |
| 9:3:3:1 | the ratio produced by crossing dihybrid F1 individuals to produce the F2 progeny |
| Mendel's Second Law | different gene pairs assort independently in gamete formation (this works more for genes on different chromosomes than the same chromosome) |
| Modern form of Mendel's Second Law | gene pairs on different chromosome assort independently at meiosis |
| product rule | the probability of independent events both occurring together is the product of their individual probabilities |
| sum rule | the probability of either of two mutually exclusive events occurring is the sum of their individual probabilities |
| chi-square test or X^2 test | a statistical test that checks the ratios against expectations (a hypothesis will usually be rejected as false if there is a probability of less than 5% of observing a deviation from expectations at least as large as the one actually observed |
| degrees of freedom | the number of these is the number of independent variables in the data |
| probability value | the probability of observing a deviation from the expected results at least as large (not exactly this deviation) on the basis of chance if the hypothesis is correct |
| X^2 test | depends on sample size... must use actual numbers, not proportions or percentages |
| pure lines | only these homozygous lines express recessive alleles |
| hybrid vigor | the general superiority of multiple heterozygotes |
| heteromorphic pair | a chromosome "pair" that has nonidentical members (as in grasshoppers) |
| independent assortment | seen in meiosis... the first division into gametes |
| independent assortment | there are two equally frequent allelic segregation patterns |
| meiosis | produces 1:1:1:1 ratio (in F1 generation) |
| ascus | a membranous sac that holds the spores together |
| independent assortment in meiocytes | further proven by 50% frequency of each genotype frin tge criss of fungi |
| Neurospora | forms an octad of four spore pairs (go through mitosis after they go through meiosis) |
| hyphae | branched threads that come from neurospora during germination |
| haploid state | shows mutations directly in the phenotype |
| 2 sexes of neurospora interact | their cell walls and nuclei fuse, resulting in many transient diploid nuclei, each of which undergoes meiosis |
| ascospores | germinate and produce colonies asexually |
| recombination | the production of new allele combinations |
| meiotic recombination | any meiotic process that generates a haploid product with new combinations of the alleles carried by the haploid genotypes that united to form the meiocyte |
| recombinant | any meotic product that has a new combinations of alleles provided by the input genotypes |
| diploid cycle | must know the genotypes of inputs and outputs to determine recombination |
| a recombinant frequency of 50% | indicates that the genes are independently assorting and are most likely on different chromosomes |
| continuous variation in populations | height, weight, and color intensity |
| metric, or quantitative, characters | height, weight, and color intensity |
| bell shaped curve | shows that average values in the middle are most common, whereas extreme values are rare |
| polygenes or quantitative trait loci (QTLs) | interacting genes that underly the hereditary continuous variation |
| quantitative | nearly synonymous with continuous |
| trait locus | place on a chromosome |
| polygenes | add to degree of a specific characteristic |
| variation and assortment of polygenes | can contribute to contiuous variation in a population |
| mitochondri and chloroplasts | hold a distinct and specialized subset of the genome that are inherited independently of the nuclear genome |
| extranuclear inheritance | inheritance outside of the nuclear genome (from mitochondria or chloroplasts) |
| mitochondria genes | related to the task of energy production |
| chloroplast genes | related to the function of photosynthesis |
| nucleoids | suborganelle structures where DNA is sometimes packed |
| mitochondrial DNA | mtDNA |
| chloroplast DNA | cpDNA |
| uniparental inheritance | progeny inherit organelle genes exclusively from one parent but not the other |
| maternal inheritance | inheritance from only the mother (because parents do not contribute cytoplasm equally to the zygote in extranuclear inheritance - egg contributes bulk of cytoplasma and the sperm provides essentially none) |
| cyctoplasmic inheritance pattern | mutant female x wild-type male --> progeny all mutant... wild-type female x mutant male --> progeny all wild type |
| variant phenotypes caused by mutations in cytoplasmic organelle DNA | generally inherited maternally and independent of the Mendelian patterns shown by nuclear genes |
| cytohets or heteroplasmons | cells that contain mixtures of mutant and normal organelles |
| cytoplasmic segregation | the two types apportion themselves into different daughter cells (most likely stems from chance partitioning of the daughter cell) |
| chloroplasts (four o'clocks) | inherit color of leaf based on the color of the leaf that was connected to the flower that produced the egg |
| cytohets | produce variegated progeny |
| random genetic drift | by chance, the mutation-bearing chromosome may by chance increase in frequency in the population within the cell |
| cytoplasmic segregation | organelle populations that contain mixtures of two genetically distinct chromosomes often show segregation of the two types into duaghter cells at cell division |
| alleles on organelle chromosomes | 1.N sexual crosses r inherited from 1 parent only (gen. the maternal parent)&show no segregation ratios of the type nuclear genes do 2.n asexual cells show cytoplasmic segregation 3.n asexual cells can occasionally show processes analogous 2 crossing over |
| MERRF (myoclonic epilepsy and ragged red fiber)and Kearns-Sayre syndrome | results from a single base change in mtDNA, and is thought to be a product of cytoplasmic segregation --> carried only by females, never males (both cases, the cells contain both mutant and normal chromosomes & they can be passed to progeny in dif. props. |
Created by:
Nicolekr
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