Advantages And Disadvantages Of Polyploidy

Multi celled organisms like human beings require a large amount of DNA. There are two meters of DNA in every human cell but the cell’s nucleus diameter is only 5-8 micrometers. So how does all that DNA fit into our cell’s nucleus? Well the very long double stranded DNA molecules are tightly packed into chromosomes, which are highly compacted. Chromosome 22, for example, has 48 million nucleotide pairs which, if stretched out end to end the DNA would extended 1.5 cm. Chromosome 22 during the stage of mitosis it measures at an astonishing 2 micrometers. This is ten thousand times tighter then if the DNA was stretched out all the way. DNA has the assistance of the chromosomal proteins, histones

Human cells carry two copies of each chromosome they have two versions of each gene and the different versions are called alleles. Alleles can be either dominant or recessive. Dominant alleles means you have one copy of the gene or your heterozygous. Recessive alleles means you have two copies of the gene or your homozygous.

Chromosomes are structures inside cells that are made of genes. They carry the genetic information about how the body develops. Normal cells have 23 pairs of chromosomes in each cell. Having an extra chromosome in all or some cells (mosaicism) changes the way these cells develop and function. It interferes with normal growth and development while a baby is in the womb. Trisomy 13 and 18 lead to a number of serious developmental defects. These defects make survival unlikely beyond the first year of life.

Meiosis is only performed by a male or female’s sex organs because the cells found in those organs, gametes, contain the X or Y chromosomes (Maayan 2011). When the gametes are producing more cells, they pass on the X or Y chromosomes to the new haploid daughter cells. Randomly, during miosis I or meiosis II, the homologue pairs or the chromatids do not separate in a process called nondisjunction (Mader 2015). When this occurs occurs and some new cells will be left with no chromosomes and others with double the amount of chromosomes. If a woman has an egg with no x chromosome is fertilized or if a sperm with no X chromosome fertilizes an egg, what will result is a zygote with only one X chromosome instead of the normal two (“Chromosomal Abnormalities” 2017). If this zygote is formed, it is called monosomy X or what we know as Turner Syndrome (“Chromosomal Abnormalities”

A karyotype is the number of chromosomes within the nuclei of a cell. This has to be seen in order to view each chromosome and determine the number of chromosomes within each nucleus. This helps to determine how genetic material will be divided among the newly forming cells.

Homologous chromosomes are similar but not identical. Each carries the same genes in the same order, but the alleles for each trait may not be the same. In garden peas, for example, the gene for pod color on the maternal chromosome might be the yellow allele; the gene on the homologous paternal chromosome might be the green allele. One chromosome of each homologous pair comes from the mother (called a maternal chromosome) and one comes from the father (paternal chromosome). Homologous chromosomes are similar but not identical. Each carries the same genes in the same order, but the alleles for each trait may not be the same. In diploid organisms, the genome is composed of homologous chromosomes. One chromosome of each homologous pair comes from

Meiosis is a cell division that results in four daughter cells. The daughter cells have half the number of chromosomes of the parent cells.In meiosis the Law of Independent Assortment states that the alleles of one gene sort in gametes independently of the alleles of another gene. Meiosis increases inherited genetic variation because during meiosis, homologous chromosomes each from one pair of parents. The parents chromosomes cross over and and trade some genes when they break apart. This recombination of forming together then breaking apart and

They are present as an interwoven mass, such that the individual chromosomes can not be identified. This mass stains lightly with basic dyes and is known as chromatin. The chromatin is heterogeneous, i.e. it consists of relatively deep and light staining regions.

containing only one member of each chromosome pair) trophic forms that grow into bigger, diploid (i.e. containing two members of each chromosome pair) trophic forms and reproduce asexually by cell division. During ultrastructural studies investigators have described the shape of trophic form as pleomorphic or amoeboid, and the shape of large trophic forms often appears quite irregular during electron microscopy.

Unit III: Genetics (15 Lectures) 3.1: Gene and gene concepts, definition of gene and gene expression 3.2: Mendelian inheritance: i) Monohybrid and dihybrid cross, ii) Concept of dominance, iii) Exception to Mendelian inheritance: Incomplete dominance, co- dominance, interaction of genes: (Epistasis:

A change in a chromosome number is known as Aneuploidy. Aneuploidy is a genetic condition where an organism acquires fewer or more chromosomes than the normal diploid number. A monosomic organism has one less than the diploid number of chromosomes meaning the human zygote will have 45 chromosomes. A trisomic organism has one more than the diploid number of number of chromosomes i.e. the organism will now have 47 set of chromosome meaning there are three homologous copies of one chromosome. It can develop in many ways. For example, during mitosis a centromere can be deleted as a result a chromosome can be lost. Aneuploidy usually alters the phenotype drastically because it alters chromosome number but not the DNA sequence. Between 75 and

Chen encouraged concurrent enrollment in his graduate-level plant cytogenetics course, teaching advanced microscopy and chromosome analysis techniques. Following both experiences, we collaborated on an undergraduate research grant, winning the highest award for our directive. Over twelve weeks, I investigated a four-chromosome grass species, Zingeria biebersteiniana, containing only one linear chromosome per meiotic gamete. I spent the summer independently preparing microscopy slides for fluorescent in-situ hybridization to reveal novel DNA configurations. Although unpublished, we discovered one plant with stunted growth and apomictic asexual reproduction, indicating novel chromosome

In Angiosperms, polyploidization is a common process that leads to the evolution and speciation of species (2 to 4% of speciation cases are related to chromosome doubling (Otto and Whitton, 2000)). Polyploidy corresponds to the process in which a cell has more than two pairs of the same chromosome. This process leads to profound genetic variation and consequently, phenology, reproduction, fitness, etc also change creating an opportunity to the species improvement or even a new species/cytotype formation (___)

Polyploidy plants have been altered in such a manner that they cover a larger surface area and thus require more resources: water; space; light.

Meiosis: Meiosis is a sexual cell reproduction process whereby a single cell divides its homologous chromosomes equally to form two haploid cells with half the chromosomes of the parent cell.