chromosomes are found in the cell nucleus of a plant cell.
chromosomes are found in the cell nucleus of a plant cell.
where are chromosomes found in a plant cell?
cell nucleus
bullet::::- "agrobacterium"-mediated transformation is the easiest and most simple plant transformation. plant tissue (often leaves) are cut into small pieces, e.g. 10x10mm, and soaked for 10 minutes in a fluid containing suspended "agrobacterium". the bacteria will attach to many of the plant cells exposed by the cut. the plant cells secrete wound-related phenolic compounds which in turn act to upregulate the virulence operon of the agrobacterium. the virulence operon includes many genes that encode for proteins that are part of a type iv secretion system that exports from the bacterium proteins and dna (delineated by specific recognition motifs called border sequences and excised as a single strand from the virulence plasmid) into the plant cell through a structure called a pilus. the transferred dna (called t-dna) is piloted to the plant cell nucleus by nuclear localization signals present in the agrobacterium protein vird2, which is covalently attached to the end of the t-dna at the right border (rb). exactly how the t-dna is integrated into the host plant genomic dna is an active area of plant biology research. assuming that a selection marker (such as an antibiotic resistance gene) was included in the t-dna, the transformed plant tissue can be cultured on selective media to produce shoots. the shoots are then transferred to a different medium to promote root formation. once roots begin to grow from the transgenic shoot, the plants can be transferred to soil to complete a normal life cycle (make seeds). the seeds from this first plant (called the t1, for first transgenic generation) can be planted on a selective (containing an antibiotic), or if an herbicide resistance gene was used, could alternatively be planted in soil, then later treated with herbicide to kill wildtype segregants. some plants species, such as "arabidopsis thaliana" can be transformed by dipping the flowers or whole plant, into a suspension of "agrobacterium tumefaciens", typically strain c58 (c=cherry, 58=1958, the year in which this particular strain of "a. tumefaciens" was isolated from a cherry tree in an orchard at cornell university in ithaca, new york). though many plants remain recalcitrant to transformation by this method, research is ongoing that continues to add to the list the species that have been successfully modified in this manner.
transformation (genetics)
humans are diploid organisms, carrying two complete sets of chromosomes in their somatic cells: one set of 23 chromosomes from their father and one set of 23 chromosomes from their mother. the two sets combined provide a full complement of 46 chromosomes. this total number of individual chromosomes (counting all complete sets) is called the chromosome number. the number of chromosomes found in a single complete set of chromosomes is called the monoploid number ("x"). the haploid number ("n") refers to the total number of chromosomes found in a gamete (a sperm or egg cell produced by meiosis in preparation for sexual reproduction). under normal conditions, the haploid number is exactly half the total number of chromosomes present in the organism's somatic cells. for diploid organisms, the monoploid number and haploid number are equal; in humans, both are equal to 23. when a human germ cell undergoes meiosis, the diploid 46-chromosome complement is split in half to form haploid gametes. after fusion of a male and a female gamete (each containing 1 set of 23 chromosomes) during fertilization, the resulting zygote again has the full complement of 46 chromosomes: 2 sets of 23 chromosomes.
ploidy