Basics of Chromatids | Haploid vs Diploid Chromosomes🦠
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▬▬▬▬▬▬▬▬▬▬ Contents of this video ▬▬▬▬▬▬▬▬▬▬
The number of chromosomes is indicated by a small letter n.
Normal body cells of diploid organisms always contain pairs of homolog chromosomes. All these cells are in principe genetically identical to the zygote (the product resulting from fertilization) from which they descend. Each pair of homolog chromosome is a heritage of one set from mother side and another from father side. However, because of meiotic "reshuffling" (= crossing-overs), a different pool of genes is present in the inherited chromosomes than in the cells of the father and the mother!
Sexual reproductive cells have only one sample of each chromosome.
An unreplicated chromosome contains one double strand -DNA molecule.
A replicated chromosome contains two identical double strand DNA molecules, the chromatids, that are joined at their centromere.
Two single sets of pairs (daughter) chromosomes are formed by separation of the pair of chromatids during cell division (from anaphase on in mitosis and anaphase II in meiosis)
Haploid is the term for a cell or an organism with only one set of chromosomes (n). If this is valid for all cells, the entire organism is regarded as being haploid. A haploïde cell remains in fact n after replication, but doubles from c to 2c. Each chromosome consists of two chromatids.
Diploid is the term for cells with a double number of chromosomes (2n), whereby one set of chromosomes is homolog to the other. (The sex chromosomes present in each human cell are an exception). A diploid cell remains 2n after replication, but doubles from 2c to 4c.
Humans usually have 22 pairs of homolog chromosomes (autosomes) and as sex chromosomes 2 x chromosomes (in female), or 1 x and 1 y chromosome (in males), thus in total 46 chromosomes per body cell (see human karyogram; 2n = 46) and 92 chromatids per cell after replication.
Diploid is a term that refers to the presence of two complete sets of chromosomes in an organism’s cells, with each parent contributing a chromosome to each pair. Humans are diploid, and most of the body’s cells contain 23 chromosomes pairs. Human gametes (egg and sperm cells), however, contain a single set of chromosomes and are said to be haploid.
Diploid. A diploid cell has two complete sets of chromosomes. Most cells in humans are diploid, comprising 23 chromosome pairs, so 46 chromosomes in total. This is 22 pairs of autosomes and a pair of sex chromosomes. One copy of each chromosome pair came from the individual's mother and the other from the individual's father. Since we have two copies of each chromosome, we also have two copies of every gene. Most mammals are diploid, like humans, but some organisms are polyploid, meaning they have more than two sets of each chromosome. For example, your standard grocery store strawberry is octoploid, with eight complete sets of seven chromosomes each, or 56 chromosomes in total, if you do the math.
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