What is the difference in number of chromosomes in a body cell vs a reproductive cell? Make sure your answer covers all species not just humans.
Answers
Human somatic cells have 46 chromosomes, including 22 homologous pairs and one pair of nonhomologous sex chromosomes. This is the 2n, or diploid, condition. Human gametes have 23 chromosomes, one each of 23 unique chromosomes. This is the n, or haploid, condition.
Explanation:
Chromosomes are thread-like structures located inside the nucleus of animal and plant cells.
Introduction
When a cell divides, one of its main jobs is to make sure that each of the two new cells gets a full, perfect copy of genetic material. Mistakes during copying, or unequal division of the genetic material between cells, can lead to cells that are unhealthy or dysfunctional (and may lead to diseases such as cancer).
But what exactly is this genetic material, and how does it behave over the course of a cell division?
DNA and genomes
DNA (deoxyribonucleic acid) is the genetic material of living organisms. In humans, DNA is found in almost all the cells of the body and provides the instructions they need to grow, function, and respond to their environment.
When a cell in the body divides, it will pass on a copy of its DNA to each of its daughter cells. DNA is also passed on at the level of organisms, with the DNA in sperm and egg cells combining to form a new organism that has genetic material from both its parents.
Physically speaking, DNA is a long string of paired chemical units (nucleotides) that come in four different types, abbreviated A, T, C, and G, and it carries information organized into units called genes. Genes typically provide instructions for making proteins, which give cells and organisms their functional characteristics.
Image of a eukaryotic cell, showing the nuclear DNA (in the nucleus), the mitochondrial DNA (in the mitochondrial matrix), and the chloroplast DNA (in the stroma of the chloroplast).
Image of a eukaryotic cell, showing the nuclear DNA (in the nucleus), the mitochondrial DNA (in the mitochondrial matrix), and the chloroplast DNA (in the stroma of the chloroplast).
In eukaryotes such as plants and animals, the majority of DNA is found in the nucleus and is called nuclear DNA. Mitochondria, organelles that harvest energy for the cell, contain their own mitochondrial DNA, and chloroplasts, organelles that carry out photosynthesis in plant cells, also have chloroplast DNA. The amounts of DNA found in mitochondria and chloroplasts are much smaller than the amount found in the nucleus. In bacteria, most of the DNA is found in a central region of the cell called the nucleoid, which functions similarly to a nucleus but is not surrounded by a membrane.
A cell’s set of DNA is called its genome. Since all of the cells in an organism (with a few exceptions) contain the same DNA, you can also say that an organism has its own genome, and since the members of a species typically have similar genomes, you can also describe the genome of a species. In general, when people refer to the human genome, or any other eukaryotic genome, they mean the set of DNA found in the nucleus. Mitochondria and chloroplasts are considered to have their own separate genomes.