Chromosomes and Cell Reproduction

About 2 trillion new cells are produced in an adult human body every day. About 25 million new cells per second! Formed when older cells divide

Cell Division/Reproduction In successful cell division, the DNA in the original cells is copied and then distributed to where each new cell has a complete copy of DNA. Cell division is also known as cell reproduction

Main Cell Types: Prokaryotic: simple, single-celled organisms, no nucleus, no membrane-bound organelles Ex: Bacteria Eukaryotic: complex, single-celled or multicellular organisms, have a nucleus and membrane-bound organelles (like mitochondria, chloroplasts, etc.) Ex: Plants, animals, fungi

Types of Cells in the Body Gametes are reproductive cells (sperm and egg cells) Gametes are haploid, or only contain one set of chromosomes. The symbol n to represent one set of chromosomes. Ex: In a human gamete, n=23 Somatic cells are body cells (anything other than gametes) Somatic cells are diploid, or contain 2 sets of chromosomes. The symbol 2n represents two sets of chromosomes. Ex: In a human somatic cell, 2n=46

Cell Division/Reproduction Not all cell types use the same type of cell reproduction. Prokaryotic cells use binary fission, which is a form of asexual reproduction that produces identical offspring. In asexual reproduction, a single parent passes exact copies of all its DNA to its offspring. Eukaryotic cells use more complex methods of reproduction.

Eukaryotic Cell Reproduction DNA contains units called genes, which contain the codes that determine how a person’s body develops and functions. Chromosomes—the DNA and proteins associated with the DNA Chromosomes become visible when the cell is preparing to divide.

Eukaryotic Cell Reproduction Chromatids are two exact copies of DNA that make up the chromosomes. The chromatids are connected at a point called the centromere. Every human body cell has 46 total chromosomes (2 sets of 23). One set of chromosomes comes from the mother, and one comes from the father. Each of the 23 pairs of chromosomes consists of two homologous chromosomes. Homologous chromosomes are chromosomes that are similar in size, shape, and genetic content.

See pg. 6 in your packet

Types of Chromosomes Autosomes are chromosomes located in the somatic cells of an organism that DO NOT determine the gender of the organism. 22 of the 23 pairs of chromosomes in a human somatic cell are autosomes.

Types of Chromosomes Sex chromosomes are one pair of chromosomes that contain the genetic material that will determine the gender of the organism. Often referred to as the X and Y chromosomes. Females have two X chromosomes (XX) Males have one X and one Y chromosome (XY)

Chromosomes In humans, each of an individual’s 46 chromosomes has thousands of genes. The presence of these genes and chromosomes is essential for normal development and function.

Chromosomes A karyotype is a picture/photo of the chromosomes in a dividing cell that shows the chromosomes arranged by size

Karyotypes Karyotypes can be used to show an abnormality in chromosome number or structure. If a person has more than two copies of a chromosome, it is a condition called trisomy. A person with an extra copy of the 21st chromosome has a condition called trisomy 21, which is more commonly known as Down syndrome.