1/ The term ploidy is used in genetics do represent how many copies of each chromosome each species has. If you have only 1 copy of each like our germline cells, that is haploid. Often shown as (N). 
2/ If you have 2 copies of each chromosome like our somatic cells its called diploid (2N). Some species have more chromosomes called ploidy. The strawberry is octoploid with 8 sets of each chromosome.
3/ This becomes important as we study genetics in human disease. There can be abnormal amounts of chromosomes in some diseases. Chromosomal abnormalities account for 60% of all spontaneous abortions.
4/ The term monosomy refers to having only 1 of a specific chromosome. The only known monosomy disease to yield a viable fetus is single X chromosome or Turner syndrome.
5/ There are several genetic disorders that lead from trisomy like trisomy 13, trisomy 18 or trisomy 21 which is Down Syndrome. This starts to get important in cancer genetics where genetic instability can lead to chromosomal abnormalities.
6/ The next important component of Chromosomes is the location of their centromere. This is a key feature to each chromosome. The centromere is critical to the chromosome. Its an anchor point during DNA replication for the sister chromatids. Its also is used in mitosis.
7/ There are 4 types of centromeres and they are named by their location in the chromosome. If the centromere is right in the center, its called metacentric. If its slightly off center, it is called sub metacentric.
8/ If the centromere is closer to the end of the chromosome, then its acrocentric. If its at the very end of the centromere, then its telocentric. There are no natural telocentric human chromosomes.
9/ The last part of the chromosome is the Telomere. This is the cap on the ends of each chromosome. It plays a key role in cell division. The telomere is there to protect the ends of the DNA strands.
10/ Each time a cell copies its DNA for mitosis, the telomere gets a little shorter. This is called the hayflick limit and averages 40 to 60 times a cell can go through mitosis before it hits this limit.
11/ Once any cell hits this limit it goes into senescence which it will no longer divide which plays a role in many age related disorders. Stem cells have and enzyme that is called telomerase. This extends the telomere each time the cell divides making stem cells immortal.
12/ One of the hallmarks of cancer is when a cancer cell mutates to turn on telomerase and become immortal like stem cells.
• • •
Missing some Tweet in this thread? You can try to
force a refresh
