- modern evolutionary biology is based on genetics
Chromosomes and Genetic Materials
- there are 2 types of cells in any living organism: prokaryotic and eukaryotic
- the main difference is that prokaryotic cells, such as bacteria, lack a cell
nucleus and are unicellular, while eukaryotic cells have a nucleus and can be
unicellular or multicellular.
- eukaryotic cells can form complex systems in multicellular organisms, such
- prokaryotic cells cannot form multicellular organisms
- within the nucleus of these cells are chromosomes
- chromosomes are DNA molecules that contain hereditary information
- each eukaryotic cell can duplicate itself and its chromosomes in a complex
process known as mitosis, where cells are divided into two identical
daughter cells with the same number of chromosomes as the parent cell.
- more important to inheritance, and therefore evolutionary processes, is
meiosis, in which cellular divisions result in daughter cells with half the
chromosomes of the parent cell and which also results in the formation of
haploid cells that determine an organism’s sex (i.e. sex cells or gametes)
- meiosis provides the hereditary material passed between generations in
sexually reproducing species, like humans.
- humans typically have 23 pairs of chromosomes (46 chromosomes) in a
- a diploid cell is a cell containing two sets of chromosomes, or one set
inherited from each parent.
- females have an XX set of sex chromosomes and males have an XY set of sex
- when a gamete is made, the chromosomes first find their matched partners
and exchange some genetic materials with each other in a process called
recombination, or crossing over. This happens before fertilization takes
- DNA strands are wrapped around spool-like proteins called histones, to
form a chromosome.
- DNA contains the genetic “blueprint” necessary for specifying the sequence
of amino acids that comprise proteins.
Mutation: The Ultimate Source of Genetic Variation