BIO 121: General Biology - Study Guide
BIO 121: General Biology - Study Guide BIO 121
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This 9 page Study Guide was uploaded by Holden Hershey on Friday October 17, 2014. The Study Guide belongs to BIO 121 at Syracuse University taught by Wiles in Fall. Since its upload, it has received 687 views. For similar materials see General Biology in Biology at Syracuse University.
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Date Created: 10/17/14
Cell DivisionMitosis Cell Division how unicellular organisms reproduce Multicellular organisms depend on cell division for their development from a fertilized egg and for growth and repair Part of the cell cycle ordered sequence of even ts in the l139fe of a cell Most Cell Division Results in Genetically Identical Daughter Cells Genome genetic material DNA of a cell quotPartitioned among chromosomes one DNA molecule associated w many proteins Chromatin complex of DNA and proteins Exist in di eren t forms of condensation at dijferent times Animals Gametesone set of chromosomes Somatic Cells two sets of chromosomes Cells replicate their genetic material before they divide Each daughter cell receives a copy of the DNA Chromosomes are duplicated prior to division Produces 2 sister chromatids chromatids joined by sister chromatid cohesion and held tigh tbl by cen tromeres When the cohesion is broken the chromatids separate during cell division becoming the chromosomes of the daughter cells Eukarvotic Cell Division Mitosis Division of the Nucleus Cytokinesis Division of the Cytoplasm Process of Mitosis In terphase G1 SG2 Q Cell growth DNA syn thesis Cell continues to grow Replication of Chromosomes Q Cell completes preparations for cell division Nuclear Envelope encloses the nucleus Centrosomes are formed each contains two centrioles quotOrganize the microtubules of the spindle Prophase Chromatin fibers become tightly coiled Nucleoli disappear Iden tical sister chromatid pairs appear Mitotic Spindle forms PrometaphaseNuclear Envelope breaks apart Microtubules invade the nuclear area Each of the two chromatids have a kinetochore protein structure the centromere Microtubules jerk back and forth in preparation for metaphase Metaphasechromosomes are aligned at the metaphase plate Metaphase Plate equal distant between spindles Each chromatid has a kinetochore connected Sister chromatids are pulled apart by the shortening of the microtubules Sister chromatids separate motor proteins move along the kinetochore microtubules to opposite ends of the cell AnaphaseShortest stage Cohesion proteins are cleaved Microtubules shorten Chromosomes pull apart Telophase 2 daughter nuclei form in the cell Nuclear Envelope reappears Completion of Mitosis division of the nucleus Cvtokinesisdivision of the cytoplasm Animal cells Use of Cleavage F urrow Plant cells Use of a Cell Plate MitosisCytokinesis Terms defined Mitotic Spindle made up of microtubules Controls chromosome movement during mitosis Arises from the cen trosomes Spindle microtubules amp asters Some spindle microtubules attach to the metaphase plate Cen tromereconstricted region joins sister chromatids Kinetochoreprotein to which microtubules bind Attached to cen tromere Homologous Chromosomes similar chromosomes from separate parents Diploid Cel chromosomes are paired homologous chromosomes Similar in length shape and other features Haploid Cells contain only one member of each of the homologous chromosome pair Genesinformation units in chromosomes Instructions for the building of a protein Locussite of a gene in the chromosome Alleles di eren t forms of a gene Same loci on homologous chromosomes Crossing 0ver between homologous nonsister chromosomes Exchanges segments of DNA strands Results in genetic recombination Gene Pairs Diploid individuals genes have pairs of alleles 0n homologous chromosomes Homozygoustvvo identical alleles Heterozygous two dijferent alleles MitosisMeiosis Mitosis single nuclear division2 identical daughter cells no Crossing Over Meiosis two nuclear divisionsFour haploid cellsCrossing over occurs Prophase I Binagv Fission in Bacteria 1 DNA is replicated 2 Cell begins to elongate 3 Replication is almost complete Cell begins to divide plasma membrane begins to pinch Produces two identical prokaryotic cells Some of the proteins involved in bacterial binary fission are related to Eukaryotic ActinTubulin Likeb that Mitosis evolved from Prokaryotic cell division Study of unicellular eukaryotes shows that they may use similar methods as past ancestors E ukarvotic Cell Cycle is regulated by a Molecular Control System Signaling molecules in the cytoplasm regulates cell process Cell Cycle Control System Molecularb based Cyclic changes in regulatory proteins work as a cell cycle clock CyclinCyclin dependent kinases CDKs Clock has specific checkpoin ts where the cell cycle stops InternalExternal signaling in transduction pathways Eukarvotic Chromosomes Nucleosome J protein bead wrapped in DNA Organized into coiled loops Held together by nonhistone sca olding protein Eight histone bound together by 1 DNA 1 Nucleosome In a stringbead formation Genetics Offspring acquire genesfrom parents by inheriting Chromosomes Each gene in an organism s DNA exists at a specific locus on a chromosome In asexual reproduction a single parent produces genetically identical o spring by mitosis Sexual Reproduction combines genes from 2 parents leading to genetically diverse o spring HumanSomatic Cells diploidZsets of 23 chromosomes one from each parent Human diploid cells have 22 homologous pairs of autosomes and on pair of sex chromosomes XXfemalesXYMales 0varies Testes produce haploid gametes by meiosis Each gamete has 23 chromosomes n23 During fertilization an egg and sperm unite forming a diploid 2n46zygote Develops into a multicellular organism by mitosis Sexual l139fe cycles di er in the timing of meiosis relative to fertilization and in the point of the cycle in which and organism is produced by mitosis Meiosis reduces the number of Chromosome setsfrom Diploid to Haploid Two cell divisions Meiosis I Meiosis II Produce 4 haploid daughter cells The number of chromosome sets is reduced from 2 diploid to 4 haploid during Meiosis I the reduction division Diploid 2n46 Haploid n23 Mendel s Two laws of Inheritance Paren ts pass on to their o spring discrete genes that refrain their identity through generations Law of Segregation genes have alternative forms or alleles In meiosis the two alleles of a gene separate also in gamete formation Explains the 31 ratio in F2 phenotypes observed when monohybrids self pollinate Each organism inherits 1 allele for each gene from each parent HeterozygousAaAaBb Cc A Dominant a Recessive Homozygous AA aa AABBCC aabbcc dominant allele does not mask genotype of recessive but it controls the phenotype considered to be true breeding Law of IndependentAssortment The pair of alleles for a given gene segregates in to gametes independen tbl of the pair of alleles for any other gene In a cross between dihybrids individuals heterozygous for two genes the o spring have four phenotypes 9331 ratio Probability Laws govern Mendelian Inheritance Multiplication Rule probability of two or more events occurring together is equal to tge product of the individual probabilities of the independent single events Addition Rule probability of an event that can occur in two or more independent mutually exclusive ways is the sum of the individual probabilities Complete Dominance of one allele heterozygous phenotype same as that of homozygous dominant PP or Pp Incomplete Dominance of either allele heterozygous phenotype intermediate between the two homozygous phenotypes Example Red Flower breeds with a white ower to produce a pink ower CodominanceBoth phenotypes expressed in heterozygotes Example Blood type AB or I quotA I quotB Multiple Alleles in the population some genes have more than two alleles Example ABO blood group alleles I quotA I quotB I quot0 Pleitropv one gene a ects multiple phenotypic characters Example Sickle Cell disease Epistasis Phenotypic expression of one gene a ects the expression of another gene Example BbEe x BbEe Polvgenic Inheritance a single phenotypic character is a ected by two or more genes Expression of a genotype can be a ected by environmental in uences resulting in a range of phenotypes Pobgenic characters that are also in uence by the environment are called multifactorial characters An organisms overall phenotype including its physical appearance internal anatomy physiology and behavior re ects its overall genotype and unique environmental history Even in more complex inheritance patterns Mendel sfundamen tal laws of segregation and independent assortment still apply Analysis of famibl pedigrees can be used to deduce the possible genotypes of individual and make predictions about future o spring Such predictions are statistical probabilities Heterozygous carriers of genetic disorders Many human diseases are multifactorial meaning they have both environmental and genetic in uences that do not exactly apply to Mendel s theory of independent assortment Amniocen tesis Chronic Villus Sampling can indicate whether a suspected disorder is present in a fetus Other genetic tests can be performed after birth Gene Expression DominantAllele masks expression of recessive allele Phenotype appearance Genotype genetic constitution Mendel s Principle of Segregation two alleles of a gene separate during Meiosis and an egg or a sperm will only receive one allele Mendel s Principle of IndependentAssortment Alleles of di erent loci are distributed randomly into gametes Recombination presents generations that were not present during the parent generation Random orientation of chromosomes during Meiosis I controls where they end up as gametes Monohybrid cross if you take two heterozygous hamsters you get a 31 ration in the expression of the phenotypes but a 121 expression of the genotypes Test Cross can reveal the organisms genotype Linked Genes groups of genes that are on the same chromosome tend to be inherited together tvvo loci lined closely together same pair of homologous chromosomes independent assortment does not apply Recombination of Linked Genes can result from crossing over in Meiotic Prophase I Crossing 0ver breaking and rejoining of homologous chromosomes Linkage Map Linkage map of a chromosome shows the relative locations of genes on a chromosome measures the frequency of recombination between linked genes more likebl the farther they are apart X and YChromosomes determines sex in mammals X bearing egg Ybearing Sperm X Chromosome important genes for males and females Male receives all xlinked genes from mom Females receives all xlinked genes from both parents Multiple Genes alleles of many loci may interact Norm of Reaction a range of phenotypic possibilities from a single genotype under di erent environmental conditions Blood Count infectionaltitude level of tness Studies of Columbia Professor Morgan on Mendel s Laws Morgan worked with Drosophila Melanogaster Fruit Fb led to the Chromosome Theory of Inheritance Genes are located on chromosomes behavior of chromosomes during meiosis accoun ts for Mendel s law Sex Linked genes Unique Patterns of Inheritance Chromosomalb based sex Sex in mammas is determined by whether or not a Yis present InsectsBirdsFish have dijferent systems Sex chromosomes carry sex linked genes most on the x chromosome x lined 2 Males inherit recessive xlinked alleles will express the trait from mother color blindness One of the two x chromosomes in a female deactivates during the development of the embryo This deactivated x chromosome becomes highly condensed in to a Barr Bodv Linked genes tend to be inherited together because they are located near each other on the same chromosome Ojfspring from a F1 dihybrid testcross parental tvpes have the same combination of traits as those in the P generation Recombination types exhibit new combinations of traits not expressed in F1 individuals or individuals from the P generation For genetically linked genes crossing over between non sister chromatids during Meiosis I accounts for the observed recombinants always less than 50 of the total Order of genes on a chromosome and the relative distances between them can be deduced from recombination frequencies observed in genetic crosses this data allows the construction of linkage maps a type of genetic map the further apart genes are the more likebl their allele combinations will be recombined during cross over Alterations of Chromosome Number or structure cause some genetic disorders Aneuploidv abnormal chromosome number can result from nondisjunction during meiosis When a normal gamete unites with one containing two copies or no copies of a particular chromosome the resulting zygote and its descending cells either have one extra copy of that chromosome trisomy 2n1 or are missing a copy monosomy Zn1 Polyploidy more than two complete sets of chromosomes can result from nondisjunction during meiosis Chromosome breakage can result in alterations of chromosome structure deletions duplications inversions translocations Change in number of chromosomes per cell or in the structure of the individual chromosomes can e ect the phenotype and in some cases lead to disorders Such alterations cause Downs Syndrome Usualbl due to trisomy of the 213 chromosome Certain cause cancers associated with chromosomal translocations and various other diseases Inheritance Patterns that are an exception to Standard Mendelian Inheritance in mammals the phenotypic e ects of a small number of particular genes depend on which allele is inherited from each parent a phenomenon called Genomic Imprinting imprints are formed during gamete production with the result that one allele either maternal or paternal is not expressed in o spring The inheritance of traits controlled by genes present in mitochondria and plastids depend solely on the maternal parent because the zygotes cytoplasm containing these organelles comes from the egg Some diseases a ecting the nervous system and the muscular system are caused by defects I mitochondrial genes that prevent the cells from making enough ATP
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