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Genetics test#3
Mitosis, Meiosis, Medellian genetics
| Question | Answer |
|---|---|
| Alternative Splicing | can generate different forms of mRNA from a single pre-mRNA |
| Negative control of Alternative RNA splicing | repressor blocks splicing machinery |
| Positive control of Alternative RNA splicing | splicing machinery inefficient unless activator is present |
| Sex lethal (Sxl) transformer (tra) and doublesex (dsx) genes are | part of a hierarchy of gene regulation for sex determination in drosophila |
| Sxl gene acts as a | switch and selects the pathway of sexual development by controlling splicing of the dsx transcript in a female specific or male specific fashion |
| spliceopathies | mutations that affect regulation of splicing; can contribute to genetic disorders |
| Myotonic dystrophy | expansion of trinucleotide repeats in 3' UTR of DMPK gene. DMPK protein sequence unaffected; repeats cause toxic mRNAs |
| toxic mRNAS of myotonic dystrophy | sequester proteins that are important for splicing of other mRNAS |
| at least ___ inappropriately spliced genes cause pathology | 20 |
| control of mRNA stability | a steady state mRNA level is determined by the combination of transcription rate and rate of degradation. this is regulated in response to cellular needs. 3'UTR sequences can regulate stability |
| translation can be regulated to produce | the correct quantity of a protein |
| post-translational stability of a protein can be | modulated |
| a protein can be modified after translation to change its | structure or activity |
| RNA silencing controls gene expression through | RNA interference(RNAi) or RNA-induced transcriptional repression |
| it is estimated that ____% of human genes are regulated in part by RNA silencing | 30 |
| Mechanisms of gene regulation by RNA-induced gene silencing | 1)dicer processes dsRNAs into siRNAs&miRNAs 2)binding to RISC or RITS; one strand is degraded 3)RNAi:RISC recognizes target mRNAs(degrades or inhibits their translation) 4)Txnsilencing:RITS recognizes genomic sequences in nucleus;recruits remodelingcmp |
| RNAi technology can | create single gene defects without having to induce mutations, which allows for rapid analysis of gene function |
| animal models have shown successful RNAi treatment of | viral infection, eye diseases, cancers, inflammatory bowel disease |
| different tumor types have different | characteristic miRNA profiles |
| some cancers are defective in miRNA expression so ___ ____ may help | synthetic miRNAs |
| overexpression of genes involved in cancer can be ____ by RNAi | targeted |
| limitations of RNAi as therapy | 1)short sequences make it harder to achieve specificity and avoid off-target effects 2)wont be useful for diseases that involve LOF gene 3)delivery methods have to be worked out 4)there may be cells that are impossible to target |
| Metacentric | centromere is in the middle |
| submetacentric | centromere between the middle and end |
| acrocentric | centromere close to the end |
| telocentric | centromere at the end |
| Homologous chromosomes | are similar and carry genes for the same inherited characteristics; they are not identical because they may carry different versions of the same gene |
| sex determining chromosomes are usually not | homologous but may behave as homologs in meiosis |
| Karyokinesis | nuclear division |
| cytokinesis | cytoplasmic division |
| Prophase | centrioles divide and move apart; nuclear envelope break downs; chromosomes condense and become visible |
| sister chromatids are connected at the ______ | centromere |
| centrioles | organize spindle fibers for movement of chromosomes during meiosis and mitosis |
| Prometaphase | chromosomes move to equatorial plane of the cell |
| Metaphase | centromeres/chromosomes aligned at equatorial plane |
| kinetochore | protein assembly at the centromere; spindle fiber attachment point |
| spindle fiber attachment leads to | cohesin degradation by separase |
| _____ at the centromere prevents cohesin degradation there | shugosin |
| Anaphase | sister chromatids separate from each other; migrate to opposite poles |
| separated sister chromatids are called | daughter chromosomes |
| Telophase | daughter chromosomes arrive at the poles; citokinesis commences; chromosomes uncoil and nuclear envelope is reformed |
| Meiosis I is ______ division | reductional |
| Meiosis II is _____ division | equational |
| DNA synthesis during Interphase before Meiosis I _____________ before Meiosis II | does not occur again |
| Synaptonemal Complex | found only in chromosomes of cells undegoing meiosis; vehicle for pairing of homologs and their segregation during meiosis |
| Meiosis I | homologous chromosomes separate and move toward the poles; sister chromatids remain attached at centromeres; duplicated chromosomes reach their poles; cytokinesis occurs and two haploid daughter cells are formed |
| Meiosis II | sister chromatids in each dyad separated to opposite poles; each haploid daughter cell from meiosis II has one member of each pair of homologous chromosomes |
| Nondisjunction during meiosis I or II leads to | gametes with abnormal numbers of chromosomes |
| pairing of nonhomologous sex chromosomes ensures | that they segregate |
| Meiosis produces diversity through | crossing over and independent assortment |
| Spermatogenesis | produces 4 haploid sperm cells |
| Oogenesis | produces and egg cell and two polar bodies |
| Monohybrid crosses | involve a single pair of contrasting traits |
| Allele | different versions of a gene |
| genotype | combination of alleles |
| Phenotype | physical expression of genetic makeup |
| Homozygous | two identical alleles |
| Heterozygous | two different alleles |
| testcross | a way to determine whether an individual displaying the dominant phenotype is homozygous or heterozygous for that trait |
| Mendel's three postulates of inheritance | 1)Unit factors in pairs 2)Dominance/recessiveness 3)Segregation during gamete formation |
| Dihybrid cross | involves two pairs of contrasting traits |
| Mendel's fourth postulate states that | traits assort independently during gamete formation; all possible combinations of gametes will form with equal frequency |
| Independent Assortment leads to | extensive genetic variation; produces genetically dissimilar gametes |
| Conditional probability | the likelihood of the desired outcome when one event depends on another |
| [n!/(s!t!)]*[(a^s)*(b^t)] | n=total# of events s=#of times outcome a occurs t=#of times outcome b occurs |
| degree of freedom = | n-1 |
| Wild type | occurs most frequently in nature |
| Loss-of-function (LOF) | reduction or loss of the specific wild type function |
| Null allele | complete LOF |
| Gain of function (GOF) | enhanced WT function |
| Incomplete Dominance | offspring have an intermediate phenotype; phenotypic ratio identical to genotypic ratio |
| Tay-Sachs disease | Homozygous recessive die from hexosaminidase activity being absent; Heterozygotes appear normal but have 1/2 enzyme activity when compared to homozygous normal |
| threshold effect | normal phenotypic expression occur whenever a certain level (usually 50% or less) of gene product is attained |
| Codominance | the joint expression of two alleles of a gene in a heterozygote results in phenotypic detection of both gene products |
| Bombay phenotype | women came from parents with A and AB blood type but she had blood type O. This is possible bc she homozygous FUT1{she dont have fucose on H substance therefore she has no substrate to make a or b antigens |
| i^A allele adds | terminal sugar N-acetylgalactosamine to the H-substance |
| i^B allele adds | a terminal galactose to the H substance |
| i^O allele adds | no terminal sugars to the H substance |
| It is estimated that _____ of all genes are essential for survival | 1/3 |
| Dominant lethals | exist in things such as huntington's disease, must reproduce before subject dies |
| Epistasis | one gene masks the effect of another; or two gene pairs complement each other such that one dominant allele is required at each locus to express a certain phenotype |
| Epistatic interactions often arise because | two or more different proteins participate in a common cellular function |
| Complementation testing | determines if two mutations causing a similar phenotype are alleles of the same gene |
| Pleiotropy | expression of a single gene has multiple phenotypic effects. Ex:Marfan Syndrome |
Created by:
ESPOLADE
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