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 |