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15 Αυγ 2020 · Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA). Passed from parents to offspring, DNA contains the specific instructions that make each type of living creature unique. The term chromosome comes from the Greek ...
- Chromosome Abnormalities Fact Sheet
One cell with 46 chromosomes divides and becomes two cells...
- Infographic X Chromosome
Most human cells contain 23 pairs of chromosomes. One half...
- Y Chromosome
Some individuals have a single sex chromosome (X or 0X), or...
- Chromosome Abnormalities Fact Sheet
Each eukaryotic chromosome consists of a long linear DNA molecule associated with proteins, forming a compact complex of proteins and DNA called chromatin. Chromatin contains the vast majority of the DNA in an organism, but a small amount inherited maternally can be found in the mitochondria.
Chromosomes are found in the nucleus of every cell of our body and are made up of DNA, tightly coiled around proteins. We have 23 pairs of chromosomes altogether, and they can only be easily observed during cell division.
A very long chain of DNA can form a chromosome. In these chromosomes are areas called genes that code for specific proteins. All the different chromosomes of an organism make up that organism's genome. In other words: DNA makes up genes, genes make up chromosomes, and chromosomes make up a genome.
Each chromosome in one set is matched by a chromosome of the same type in the other set, so there are actually 23 pairs of chromosomes per cell. Each pair consists of chromosomes of the same size and shape, and they also contain the same genes. The chromosomes in a pair are known as homologous chromosomes.
Although the numbers and sizes of chromosomes vary considerably between different species (Table 4.2), their basic structure is the same in all eukaryotes. The DNA of eukaryotic cells is tightly bound to small basic proteins (histones) that package the DNA in an orderly way in the cell nucleus.
About 95% of the DNA in polytene chromosomes is in bands, and 5% is in interbands. The chromatin in each band appears dark, either because it is much more condensed than the chromatin in the interbands, or because it contains a higher proportion of proteins, or both (Figure 4-40).
