Reading Chapter 14 1 Concepts particular Be able to explain the importance of inheritance to biology and evolution in o A major problem that Darwin faced was the Blending Hypothesis which was believed at the time which supported that during evolution traits would end up becoming more similar blending instead of evolving into something else Because overtime everything would eventually become more and more similar over time is the Blending Hypothesis was true which is obviously not what we see during evolution Diversity is retained thus inheritance cannot follow this previously believed Blending hypothesis Thus a different pattern of inheritance is necessary for evolution to occur Mendelian Inheritance Be able to explain how Mendel did his experiments o Controlled Pea Plant Experiments o Normally Peas only self pollinate So he could control breeding completely So at an early stage he would cut off the male part off of the flower and then would pollinate other flowers He also would pick plants that were pure breed meaning essentially they are homozygous And every member in that plant s family were homozygous for that same trait Be able to distinguish between Mendelian inheritance and blending inheritance o The Blending Model of Inheritance is the idea that a cross between two different traits such as a purple and a white flower would yield an intermediate trait in the offspring such as the offspring having a pale purple color However Mendel was able to prove this model incorrect o Mendelian Inheritance explains how there are two alleles within a genotype that make up the phenotype for the trait An organism can be Heterozygous Have two different alleles for the trait in which the dominant trait determines the phenotype or Homozygous Having a pair of identical alleles can express the dominant or recessive phenotype Be able to explain the significance of the Law of Segregation o The two alleles for a heritable character segregate separate from each other during gamete formation and end up in difference gametes Thus an egg or sperm gets only one of the two alleles that are present in the somatic cells of the organism making gamete In terms of chromosomes this segregation corresponds to the distribution of the two members of a pair of homologous chromosomes to different gametes in meiosis o Note that if an organism has identical alleles for a particular character then that allele is present in all gametes But if different alleles are present then 50 of the gametes receive the dominant allele and 50 receive the recessive allele Terms Gene a sequence of nucleotides at a specific place or locus along a particular chromosome Allele Alternative versions of a gene Locus The DNA at a locus can vary slightly in its nucleotide sequence and thus this information content Such as how the purple flower allele and the white flower allele are two DNA sequence variations possible at the flower color locus on one of a pea plants chromosome Heterozygote An organism that has two different alleles for a gene Homozygote An organism that has a pair of identical allele for a character Can be Recessive Homozygous or Dominant Homozygous Genotype An organism s genetic makeup Phenotype An organism s observable traits appearance Dominant If the two alleles differ at the locus differ then the one dominant allele determines the organisms appearance Recessive In a Heterozygote the allele that has no noticeable effect on the organism s appearance phenotype F1 First filial Latin for son generation the hybrid offspring of two P parental generation F2 The offspring from either a F1 hybrid that self pollinized or cross pollinized with other F1 Hybrids Second Filial Generation Monohybrid Heterozygous for the one particular character being followed The offspring produced by crosses of true breeding parents Reading Chapter 13 1 13 2 Be able to distinguish between the genetic consequences of sexual and asexual reproduction offspring by mitosis o During asexual reproduction a single parent produces genetically identical o Whereas sexual reproduction combines sets of genes from two different parents leading to genetically diverse offspring Be able to distinguish the cellular processes behind asexual mitosis and sexual o Asexual reproduction occurs through mitosis while sexual reproduction occurs meiosis reproduction through meiosis Know that chromosomes exist as homologous pairs in diploids Chromosomes typically exist as homologous pairs same loci locus may have different alleles on each pair Homologous Chromosomes may not be identical Note sister chromatids are duplicated chromosomes exactly the same during the cell cycle mitosis Be able to explain why meiosis produces haploid daughter cells from diploid parents o Meiosis begins with a parent cell that is diploid meaning it has two copies of each chromosome The parent cell undergoes one round of DNA replication followed by two separate cycles of nuclear division The process results in four daughter cells that are haploid because of meiosis II which means they contain half the number of chromosomes of the diploid parent cell Know that sexual life cycles alternate meiosis and fertilization Be able to explain how sexual life cycles vary in the timing of meiosis and fertilization o In the diploid dominant cycle the multicellular diploid stage is the most obvious life stage the only haploid cells produced by the organism are the gametes o Most fungi and algae employ a haploid dominant life cycle type in which the body of the organism is haploid specialized haploid cells from two individuals join to form a diploid zygote o Observed in all plants and some algae species with alternation of generations have both haploid and diploid multicellular organisms as part of their life cycle Terms to Know Haploid Only one of each type of chromosome Diploid Pairs of homologous chromosomes diploid condition Homologous Chromosome homologous pair Genetically similar but not necessarily identical Sister chromatid Genetically identical result of S phase of cell cycle Gamete Sperm and Eggs which are vehicles that transmit genes to one generation to the next Zygote Fertilized egg Meiosis Daughter cells contain a subset of parent cell s genes Preconditions for sexual reproduction formation of gametes Produces haploid cells no homologous pairs only one of each type of chromosome Fertilization When the male and female gametes sperm and egg unit thereby passing on genes of both parents to their offspring
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