BIO 311D 1st Edition Final Exam Study Guide Lectures 1 31 Mitosis and Meiosis Lecture 1 The Stages of Meiosis 1 Interphase Chromosomes duplicate 2 Meiosis I Homologous chromosomes separate a Prophase I Chromosomes condense homologous chromosomes pair up synapsis and crossing over occurs b Metaphase I Tetrads line at metaphase plate microtubules attach to kinetochores c Anaphase I Pairs of homologous chromosomes separate and move toward pole by spindle apparatus d Telophase I Cytokinesis Cleavage furrow divides the cell into two 3 Meiosis II Sister chromatids separate a Prophase II Spindle apparatus forms b Metaphase II Sister chromatids due to crossing over sister chromatids are no longer identical align at the metaphase plate and microtubules attach to kinetochores c Anaphase II Sister chromatids separate and move towards opposite poles d Telophase II Cytokinesis Nuclei form and chromosomes decondense Each daughter cell is genetically different from the others Comparing Mitosis and Meiosis Property DNA Replication Number of Divisions Synapsis of Chromosomes Number of Daughter Cells Role in the Animal Body Mitosis Interphase One None Two Identical Growth Repair Meiosis Interphase Two Prophase I Four Unique Produces Gametes Characteristics Unique to Meiosis all occur in Meiosis I 1 Prophase I Synapsis and crossing over occurs 2 Metaphase I Tetrads paired homologous chromosomes line up at the metaphase plate 3 Anaphase I Homologous chromosomes separate instead of sister chromatids Mendel and the Gene Idea Lectures 2 3 Advantages of pea plants 1 2 3 4 Many varieties with distinct heritable features Mating can be controlled Each flower has sperm producing organs stamens and egg producing organs carpel Cross pollination fertilization between different plants involves dusting one plant with pollen from another The Law of Segregation Two alleles for a heritable character segregate during gamete formation and end up in different gametes Discovered by using monohybrids crosses between one character The white color trait did not disappear but rather it was recessive Mendel called the purple flower the dominant trait The white colored flower became the recessive trait The 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 together DEFINITIONS YOU SHOULD KNOW Monohybrid cross A cross between individuals for one trait ratio of 3 1 Dihybrid Cross A cross between individuals for two traits ratio of 9 3 3 1 Complete Dominance Occurs when phenotype of the heterozygote and dominant homozygote are identical Incomplete Dominance Phenotype of F1 hybrids is somewhere between the phenotype of two parental varieties Codominance Two dominant alleles affect the phenotype in separate distinguishable ways Multiple Alleles Most genes exist in populations in more than two allelic forms Pleiotropy Most genes have multiple phenotypic effects Epistasis A gene at one locus alters the phenotypic expression of a gene at a second locus Polygenic Inheritance An additive effect of two or more genes on a single phenotype Chromosomal Basis of Inheritance Lectures 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 chromosomes are the location of Mendel s heritable factors Advantages of breeding fruit flies o Fruit flies produce many offspring o A generation can be bred every two weeks o They only have four pairs of chromosomes X and Y chromosome Important information over Chromosomes X is larger than Y although they have the same amount of genes Karyotype is a complete set of chromosomes in the cell X linked disorders tend to be more common in males than females Given a fly with a gray body and normal wings and another fly with a black body and vestigial wings what will the F1 generation look like Test cross this F1 generation what would the offspring look like X Inactivation in Female Mammals Because females have XX one X becomes inactive Inactive x condenses into a barr body One of the two x chromosomes in each cell is randomly inactivated Example Female cats can have certain spots where she is brown and other spots where she is orange This is due to the inactivation of random X chromosomes Mapping the Distance Between Genes Using Recombination Data 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 frequency o Map units indicate relative distance order NOT the precise location of genes The Evolution of Populations Lectures 6 7 Microevolution A change in allele frequencies in a population over generations The Hardy Weinberg equation Can be used to test whether a population has evolved The frequency of an allele in a population can be calculated o 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 frequencies o P is in reference to dominance o Q is used in reference to the recessive allele o P Q will always equal 1 For example consider a population of wildflowers that is incompletely dominant for color o 320 red flowers CRCR o 160 pink flowers CRCW o 20 white flowers CWCW Calculate the number of copies of each allele o CR 320 2 160 800 o CW 20 2 160 200 To calculate the frequency of each allele o p freq CR 800 800 200 0 8 o q freq CW 200 800 200 0 2 The sum of alleles is always 1 o 0 8 0 2 1 Example 1 in 1700 US Caucasian newborns have cystic fibrosis C for normal is dominant over c for cystic fibrosis 1 When counting the phenotypes in a population why is cc the most significant cc reveals all the individuals who are homozygous recessive and therefore have cystic fibrosis 2 What percent of the above population have cystic fibrosis cc or q 2 1 1700 0 0588 this is q