The mechanisms responsible for the origin and maintenance of large non-recombining regions on sex chromosomes have been mostly studied in plants and animals, but the recent discovery of similar features on the fungal chromosomes carrying mating type genes in several species may shed new light on this phenomenon (Fraser et al. 2004). Sex chromosomes in plants and animals have evolved from an autosomal pair by the expansion of the non-recombining region around complementary genes determining sex-specific functions (Bergero and Charlesworth 2009). Such a multi-step expansion of the non-recombining regions in sex chromosomes, forming “evolutionary strata” (Lahn and Page 1999), is usually explained by the recruitment of genes determining sexually antagonistic traits (i.e. beneficial in males and deleterious in females, or conversely), via a selection for linkage to the sex-determining genes (Rice 1987, Charlesworth 2005). Selective forces driving the evolution of non-recombining regions are however likely to be different in fungi as cells of different mating types exhibit little phenotypic differences.
In heterothallic fungi, syngamy can only occur between haploid cells carrying different alleles at the mating type genes, while in homothallic fungi, no such differences are required, allowing universal compatibility (Billiard et al. 2011). The two main fungal phyla have different mating type genes and organization: a single locus controls mating type in ascomycetes against two loci in basidiomycetes (i.e. haploid cells should carry different alleles at both loci for successful mating). One of the two loci controlling mating types in basidiomycetes encodes pheromones and pheromone receptors involved in syngamy while the other locus...
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...Smith et al. 2004) and Cryptococcus neoformans (Wang et al. 2002). In R. toluroides, the gene encoding ste20 is surrounded with genes encoding pheromones (Coelho et al. 2008). Other genes, such as the abc1, with more elusive role in mating and development of fungi have also been found in close proximity to the genes encoding the pheromone and its receptor in R. toluroides (Coelho et al. 2008).
In this study, our goals were therefore to: 1) identify additional genes belonging to the mating type locus in Microbotryum, in particular the genes encoding the pheromones and the homeodomain proteins, all of which control mating types in most basidiomycetes, 2) assess whether the genealogies of genes in the mating type region as well as of loci of the previously proposed strata are consistent with the existence of evolutionary strata along the mating type chromosomes.
This paper analyzes whether or not gene to map distance in Sordaria fimicola is affected by changes in environmental conditions. The main focus is on how temperature affects the recombination frequency in this organism. It is analyzed if under different environmental conditions wt x gray and wt x tan varies in their percent crossing over. It is investigated how factors such as temperature and ultraviolet light have affected the gene to centromere distance in Sordaria. Results obtained in lab as well as scientific researches prove that as temperatures increases the percent of crossing over increases as well.
Sordaria fimicola is a species of microscopic fungus that is an Ascomycete and are used to test for genetic variation in the lab setting (Sordaria fimicola: A Fungus used in Genetics, Volk). These organisms are what are called model organisms, or species that has been widely studied usually because it is easy to maintain and breed in a laboratory setting and has particular experimental advantages (Sordaria fimicola, Volk). S. fimicola, because it is in the Ascomycota phylum, have a distinguishing reproductive structure called the ascus, which is surrounded by the perithecium. This cylindrical sac-like structure houses 8 haploid spores; created through meiosis to produce 4 haploid spores and then mitosis to make 8 (Lab Manual, pg. 59-68). Based on the genotype they will vary in order and color. There are 3 different ratios that can arise from the 8 ascospores: 4:4, 2:2:2:2, and 2:4:2 (black/wild type and tan coloration). The 4:4 ratio suggests that no crossing over had occurred because there is no difference in order of the color parents that were mated. The two other ratios suggest genetic recombination, or crossing over, because of the
The fungus Sordaria fimicola is commonly used to study the different processes of cell cycles such as the assortment of genes and the crossing over during meiosis. Considering the importance of genetics in the world today, this experiment is crucially valuable in helping the students gain knowledge in the different processes of cell cycle and learning how to attempt similar experiments on their own in the future. Sordaria fimicola requires “both mitotic and meiotic nuclear divisions to manufacture eight haploid ascospores” (Helm, 1998). This fungus “spend most of its life in haploid condition” (Glase, 1995). When the haploid nuclei fuse together in the cells, they beco...
The idea of the project was to experiment breeding Drosophila Melanogaster (fruit fly) to figure out if certain genes of that species were sex linked or not (autosomal). A mono-hybrid cross and di-hybrid cross was performed. For the mono-hybrid cross, white eyed female and red eyed male were placed in one vial for them to reproduce. For the di-hybrid cross, red eyed and normal winged flies and sepia eyed and vestigial winged flies were placed in their vial to reproduce. In the mono-hybrid cross the results expected were within a 1:1:1:1 ratio. Expected results similar to the expected desired null hypothesis proposed with what the F1 parental generation breeds. The potential results would have had to have been within the ratios of 9:3:3:1. The results were clear and allowed the null hypothesis to be correct. The white eyed gene in the fruit flies is sex linked. Sepia eyes and vestigial wings are not sex linked and are examples of independent assortment.
2)Campbell, Neil A., and Jane B. Reece. Biology. San Francisco, CA: Benjamin Cummings, 2008. Print.
As the population density increased, so did the male gametophytes of the wild type strain; but there were no male gametophytes at any population density in the Her ...
Nettie studied Tenebrio molitor beetles and found that unfertilized eggs in female beetles always contain an X chromosome. Sperm from male beetles contain either an X chromosome or a Y chromosome. She found that eggs fertilized by sperm carrying the X chromosome produce female beetles. The combination of egg and Y-chromosome sperm produce male beetles.
6 Jones, M. , Fosbery, R. , Taylor, Dennis. , (2007), Biology 1, Cambridge University Press, Cambridge
The fruit fly better known by geneticist as Drosophila melanogaster, is a very common model used to study genetic inheritance. It is perfect for studying inheritance patterns because of its tiny size and rapid reproduction. They also have many distinct characteristics between genders which makes viewing inheritance patterns easier. Males are small with dark bottoms and tend to have sex combs on their legs. Females are large with stripped bottoms, and pointed bodies. When dealing with the fruit flies they need to be kept in certain temperatures and the lab incubator/refrigerator helps sustain a good temperature. Like humans, the fruit fly has four pairs of chromosomes, one of which is the sex chromosomes.
This lab report dealt with the analyzation and transmission of genetic traits in monohybrid and dihybrid crosses using Caenorhabditis. Mutations will be either dominant or recessive or X-linked or autosomal. Where using a sterile pick you will pick certain worms and place them in a new petri dish for them to reproduce and observe new progenies, mutations and different crosses.
The amoebae feed on bacteria that secrete folic acid which attracts them. When the supply of bacteria runs out, the amoebae aggregate to form a multicellular fruiting body composed of a stalk and a spore containing sorus. This aggregation begins with the secretion of Cyclic AMP (cAMP) by a few cells which attracts other amoebae to them. They clump together and form what is called a Dictyostelium discoideum slug with anywhere from 100 to 2,000,000 amoebae in it that has motility due to a cellulose sheath secreted by the cells. It migrates towards light and heat, meaning the surface of the soil and once it is there the cells begin to differentiate into pre-stalk and pre-spore cells. The stalks grow upwards as high as they can to spread spores as far as possible to a more favorable environment, one with more bacteria. The farther the spores travel, the more likely they are to find a bacteria rich location. Genetically Dictyostelium discoideum has 6 chromosomes and is closely related to higher metazoans (a subkingdom of multicellular animals with differentiated cell types as well as usually a digestive tract and nervous system) which makes it a good candidate for genetic
Michener, William K. and Haeuber, Richard A., Bioscience. American Institute of Biological Science. Sep98. Vol. 48. Issue 9. p677.
In this experiment, Mendelain Models are observed. The purpose of the experiment is to understand how traits are passed from one generation to the other as well as understanding the difference between sex linked and autosomal genes. One particular trait that is observed in this experiment is when a fly is lacking wings, also known as an apterous mutation. In this experiment, we will determine whether this mutation is carried on an autosomal chromosome or on a sex chromosome. The data for this experiment will be determined statistically with the aid of a chi-square. If the trait is autosomal, then it will be able to be passed to the next generation on an autosomal chromosome, meaning that there should be an equal amount of male and
The next step includes the two nuclei of the dikaryon fusing through karyogomy (Ross 146). The resulting diploid zygotic nucleus then undergoes meiosis, and four haploid nuclei are formed in the basidium (Webster 280). The haploid nuclei move into projections on the basidium, which turn into spores. The spores are attached to the sterigmata until they are released (Ross 146). The cycle then starts over again.
During prophase I, homologous chromosomes pair and form snynapses. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. The bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent.