Chapter 8 Cell Reproduction Section 1 Chromosomes

Chromosome Structure Chromosome- rod-shaped structure made of DNA and proteins If DNA were stretched out, it would be 6 feet long!! How does it fit into the nucleus of a cell?

Histone proteins DNA is tightly coiled around histone proteins *These proteins help maintain the shape of chromosomes The red structures are histone proteins

DNA molecules are coiled on many levels to form chromosomes

Chromatid-each identical half of a chromosome

Centromere-a structure that holds two chromatids together

chromatin -less tightly coiled DNA; DNA exists as chromatin when it is not coiled into chromosomes

Prokaryotic DNA… …is a circle and consists of one chromosome

Every species has a unique number of chromosomes… How many do we have? 46 chromosomes Or 23 pairs of chromosomes

Does the number of chromosomes indicate the complexity of an organism? Adder’s tongue fern 1,262 Carrot 18 Cat 32 Chimpanzee 48 Dog 78 Earthworm 36 Fruit fly 8 Organism Number of Chromosomes Garden pea 20 Gorilla 48 Horse 64 Human 46 Lettuce 18 Orangutan Does the number of chromosomes indicate the complexity of an organism?

Types of chromosomes XX XY We have 1 pair or 2 chromosomes They are X and Y XX XY 1. Sex Chromosomes-chromosomes that determine the sex of an individual

2. Autosomes-They control everything about us except for our sex Ex. Eye color We have 22 pairs or 44 autosomes

The Structure of a Chromosome Two Chromosomes similar in size and shape that make up a pair are called Homologous chromosomes

Here is a picture of someone’s chromosomes… Do you see the autosomes? Do you see the sex chromosomes?

A picture of a person’s chromosomes… Which one is male and which one is female? is called a karyotype

What info. is given by a karyotype? Missing parts of chromosomes Extra chromosomes Sex of offspring Down Syndrome-caused by 3 chromosomes #21

Diploid and Haploid Cells Diploid- a full set of chromosomes from both parents (2n) Haploid- one set of chromosomes (1n) Egg and sperm cells are haploid; all other cells are diploid

Cell Division 25 million cells are produced by an adult human body every day Growth and development are achieved by cell division

The division of prokaryotic cells Binary fission- the division of a prokaryotic cell into two offspring cells

Mitosis Results in two identical cells from a parent cell Occurs for development, cell repair, or asexual reproduction

Meiosis- the production of egg and sperm cells Allows chromosome number to be reduced to half. In us, 23 chromosomes are contained in our sex cells Meiosis produces gametes which are sex cells

The Cell Cycle-repeating set of events in the life of a cell Includes interphase, mitosis and cytokinesis

The Cell Cycle Interphase- a cell spends most its time in interphase G1- offspring cells grow to mature size S- DNA is copied (synthesized) G2- cell prepares to divide

Continued… Mitosis Prophase Metaphase Anaphase Telophase

prophase telophase metaphase interphase anaphase 1 2 3 4 5 What type of cell is shown; plant or animal? How do you know? interphase anaphase

Cytokinesis- the division of the cytoplasm and organelles; begins with a cleavage furrow in animal cells and a cell plate in cell walls