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Genetics test#3

Mitosis, Meiosis, Medellian genetics

QuestionAnswer
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 on 2012-03-22



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