BIO 311D 1st Edition Exam 1 Study Guide: Lectures 1- 9 Lecture 1The Stages of Meiosis:1. Interphase: Chromosomes duplicate2. Meiosis I: Homologous chromosomes separatea. Prophase I: Chromosomes condense, homologous chromosomes pair up (synapsis), and crossing over occursb. Metaphase I: Tetrads line at metaphase plate, microtubules attach to kinetochoresc. Anaphase I: Pairs of homologous chromosomes separate and move toward pole by spindle apparatus3. Telophase I/Cytokinesis: Cleavage furrow divides the cell into two Meiosis II: Sister chromatids separatea. Prophase II: Spindle apparatus formsb. Metaphase II: Sister chromatids (due to crossing over, sister chromatids are no longer identical) align at the metaphase plate and microtubules attach to kinetochoresc. Anaphase II: Sister chromatids separate and move towards opposite polesd. Telophase II/Cytokinesis: Nuclei form and chromosomes decondense*Each daughter cell is genetically different from the othersComparing Mitosis and Meiosis:Property Mitosis MeiosisDNA Replication Interphase InterphaseNumber of Divisions One TwoSynapsis of Chromosomes None Prophase INumber of Daughter Cells Two (Identical) Four (Unique)Role in the Animal Body Growth, Repair Produces GametesCharacteristics Unique to Meiosis (all occur in Meiosis I):1. Prophase I: Synapsis and crossing over occurs2. Metaphase I: Tetrads (paired homologous chromosomes) line up at the metaphase plate3. Anaphase I: Homologous chromosomes separate instead of sister chromatidsMendel and the Gene IdeaLectures 2-3Advantages of pea plants:1. Many varieties with distinct heritable features2. Mating can be controlled3. Each flower has sperm producing organs (stamens) and egg producing organs (carpel)4. Cross pollination (fertilization between differentplants) involves dusting one plant with pollen fromanotherThe Law of Segregation:- Two alleles for a heritable character segregate duringgamete formation and end up in different gametes- Discovered by using monohybrids (crosses betweenone character)- The white color trait did not disappear but rather itwas recessive- Mendel called the purple flower the dominant trait- The white colored flower became the recessive traitThe Law of Independent Assortment:- Dihybrid cross determines whether two characters are transmitted to offspring as a package or independently- Dihybrid cross was used to discover the law of independent assortment- Found that each pair of alleles segregates independently of each other during gamete formation- However, genes located near each other on the same chromosome tend to be inherited togetherWhy are humans not good subjects for genetic research?- Generation time is too long- Parents produce relatively few offspring- Breeding experiments are unacceptableMultiple Alleles:- Example is the four phenotypes ofthe ABO blood group aredetermined by three alleles for theenzyme I that attaches A or Bcarbohydrates to red blood cellsPleiotropy:- Most genes have multiplephenotypic effects known asPleiotropy- This is responsible for multiple symptoms of certain hereditary diseases- Examples include cystic fibrosis and sickle cell diseaseEpistasis:- Some traits may be determined by two or more genes- One gene at a locus alters the phenotypic expression of a gene at a second locus- In other words, one gene determines whether or not that trait is shown- Example: Labrador Retrievers and their coat coloro One gene determines the pigment color (either black or brown)o The other gene determines if the color is shownPolygenic Inheritance:- Quantitative characters are those that vary in population- Quantitative variation indicates polygenic inheritance- Example: Skin colorChromosomal Basis of InheritanceLectures 4-5 Morgan’s Experimental Evidence:- Thomas Hunt Morgan (an embryologist) found evidence associating a specific gene with a specific chromosome- He performed an experiment with fruit flies which provided evidence that chromosomesare the location of Mendel’s heritable factors- Advantages of breeding fruit flies:o Fruit flies produce many offspringo A generation can be bred every two weekso They only have four pairs of chromosomesX Inactivation in Female Mammals:- Because females have XX, one X becomesinactive- Inactive x condenses into a barr body- One of the two x chromosomes in eachcell is randomly inactivated- Example: Female cats can have certainspots where she is brown and other spotswhere she is orange. This is due to theinactivation of random X chromosomesMapping the Distance Between Genes UsingRecombination Data:- Alfred Sturterant (Morgan’s Student) constructed a genetic map- Genetic map is an ordered list of genetic loci along a particular chromosome- He predicted that the farther apart two genes are, the higher probability that a crossover will occur between them, therefore a higher recombination frequency- Linkage map: Genetic map of a chromosome based on recombination frequencies- Map Units: Distances between genes o One centimorgan represents a 1%recombination frequencyo Map units indicate relativedistance/order, NOT the preciselocation of genes- Cytogenetic maps indicate the positions ofgenes with respect to chromosomalfeaturesExceptions to Mendelian Genetics:- Two normal exceptions are:1. Genes located in the nucleus2. Genes located outside the nucleus- In both cases, the sex of the parentcontributing an allele is a factor in the patternof inheritanceGenomic Imprinting:- The phenotype depends on which parentpassed along the alleles for those traits- Involves the silencing of certain genes that arestamped with imprint during gameteproduction- It appears that imprinting is the result of themethylation (addition of —CH3) of cysteinenucleotides- Thought to affect a small fraction of mammalian genes- Most imprinted genes are critical for embryotic developmentThe Evolution of PopulationsLectures 6-7The Hardy-Weinberg equation:- Can be used to test whether a population has evolved- The frequency of an allele in a population can be calculatedo For diploid organisms the total number of alleles at a locus is the total number of individuals times 2- By convention, if there are 2 alleles at a locus, p and q are used to represent their frequencieso P is in reference to dominanceo Q is used in reference to the recessive alleleo P + Q will always equal 1- For example, consider a population of wildflowers that is incompletely