Unit 5: Cell Growth and Development 5 Unit 5: Cell Growth and Development 5.1 Chromosomes and Cell Reproduction

Why do cells reproduce? Growth Development Repair

Cell Division and Reproduction Growing cells divide to form two daughter cells. Cell copies DNA prior to dividing Cell Division and Reproduction

Asexual Reproduction Production of genetically identical offspring Examples: bacteria (binary fission), some fungi, some plants, and even some animals! Asexual Reproduction

Offspring with genetic information from each parent Examples: most plants and animals Sexual Reproduction

There are advantages and disadvantages to each reproductive strategy!

Genetic information (DNA) bundled into packages Chromosomes

Prokaryotic Chromosomes No nucleus; DNA molecules found in the cytoplasm Most contain a single, circular DNA chromosome Prokaryotic Chromosomes

Eukaryotic Chromosomes Contain multiple chromosomes in a nucleus Chromatin: complex of chromosomes and protein (histones) DNA tightly coils around histones, forming bead-like structures (nucleosomes), which pack together to form chromosomes Eukaryotic Chromosomes

Chromosomes make it possible to separate DNA precisely during cell division

Homologous Chromosomes Chromosomes in female parent have corresponding chromosomes in male parent Similar but not identical Each carries the same genes in the same order, but have different alleles for each trait. Homologous Chromosomes

Diploid “Two sets”- contain both sets of homologous chromosomes In humans: 23 from mom and 23 from dad for a total of 46. Symbol 2n Somatic cells: cells that are NOT used in reproduction Diploid

Haploid “One-set”- contains only a single set of chromosomes Symbol: n Gametes: cells used in reproduction Haploid