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Duplications arise from an event termed unequal crossing-over that occurs during meiosis between misaligned homologous chromosomes. The chance of it happening is a function of the degree of sharing of repetitive elements between two chromosomes. The products of this recombination are a duplication at the site of the exchange and a reciprocal ...
This image shows haploid (single), diploid (double), triploid (triple), and tetraploid (quadruple) sets of chromosomes. Triploid and tetraploid chromosomes are examples of polyploidy. Polyploidy is a condition in which the cells of an organism have more than two paired sets of chromosomes.
We also know that the replication-timing program changes during development, along with changes in the expression of genes. For many decades now, it has been known that replication timing is correlated with the structure of chromosomes. For example, female mammals have two X chromosomes. One of these is genetically active, while the other is ...
Non-homologous end joining can also join two different chromosomes together that had broken ends. The reason non-reciprocal translocations are dangerous is the possibility of producing a dicentric chromosome – a chromosome with two centromeres. When dicentric chromosomes form, a series of events can occur called a breakage-fusion-bridge cycle ...
As the cell divides, the telomeres on the ends of chromosomes shorten. The Hayflick limit is the limit on cell replication imposed by the shortening of telomeres with each division. This end stage is known as cellular senescence. The Hayflick limit has been found to correlate with the length of the telomeric region at the end of chromosomes.
The thick lines are chromosomes, and the thin blue lines are fibers pulling on the chromosomes and pushing the ends of the cell apart. The cell cycle in eukaryotes: I = Interphase, M = Mitosis, G 0 = Gap 0, G 1 = Gap 1, G 2 = Gap 2, S = Synthesis, G 3 = Gap 3. Cell division is the process by which a parent cell divides into two daughter cells. [1]
Because bacteria have circular chromosomes, termination of replication occurs when the two replication forks meet each other on the opposite end of the parental chromosome. E. coli regulates this process through the use of termination sequences that, when bound by the Tus protein , enable only one direction of replication fork to pass through.
Linear chromosomes are also in some ways disadvantageous or problematic, one of the biggest potential issues being the end replication problem. This is a phenomenon which occurs due to the directionality of DNA replication enzymes, resulting in the gradual loss of genetic material at the ends of linear chromosomes after each subsequent cycle of ...