1. KEY CONCEPT Cells work together to carry out complex functions. 5.5 Multicellular Life

2. Multicellular organisms depend on interactions among different cell types. Tissues are groups of cells that perform a similar function. Organs are groups of tissues that perform a specific or related function. Organ systems are groups of organs that carry out similar functions. CELLTISSUEORGAN 5.5 Multicellular Life

3. Specialized cells perform specific functions. Cells develop into their mature forms through the process of cell differentiation. Cells differ because different combinations of genes are expressed. A cell’s location in an embryo helps determine how it will differentiate. Outer: skin cells Middle: bone cells Inner: intestines 5.5 Multicellular Life

4. Stem cells are unique body cells. have the ability to –divide and renew themselves –remain undifferentiated –develop into a variety of specialized cell types 5.5 Multicellular Life

5. Stem cells - three types. –Totipotent - grow into any other cell type –Pluripotent - grow into any cell type but a totipotent cell –Multipotent - grow into cells of a closely related cell family 5.5 Multicellular Life

6. First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules. Stem cells come from adults and embryos. –Adult stem cells can be hard to isolate and grow. –adult stem cells may prevent transplant rejection. –embryonic stem cells raises ethical issues 5.5 Multicellular Life

7. The use of stem cells offers many currently realized and potential benefits. –used to treat leukemia and lymphoma. –may cure disease or replace damaged organs. –may revolutionize the drug development process. 5.5 Multicellular Life

8. Body cells - somatic cells. Sex cells = Germ cells develop into gametes. –located in the ovaries and testes. –egg and sperm. body cells sex cells (sperm) sex cells (egg) 6.1 Chromosomes and Meiosis

9. Haploid (n) cells have one copy of every chromosome. Human n = 23 6.1 Chromosomes and Meiosis Gametes are haploid.

10. Somatic cells are diploid Diploid (2n) - cells have two copies of every chromosome. Human 2n = 46 Fertilization between egg and sperm occurs in sexual reproduction. 6.1 Chromosomes and Meiosis

11. n (sperm cell)+n (egg cell) =2n (fertilized egg) Haploid+Haploid=Diploid Gamete+Gamete=Zygote 6.1 Chromosomes and Meiosis

12. Chromosome – rod-shaped structures made of DNA & protein Histones – (protein) help maintain the shape of the chromosome and aid in the tight packing of DNA DNA double helix DNA and histones Chromatin Supercoiled DNA 5.2 Mitosis and Cytokinesis

13. One half of a duplicated chromosome is a chromatid. Sister chromatids are held together at the centromere. Telomere – (4) the tips of the chromatids keep the chromosome from unwinding 5.2 Mitosis and Cytokinesis

14. Anatomy of a Chromosome X Telomere Centromere Chromatid Telomere Chromosome 5.2 Mitosis and Cytokinesis

15. QTL – Quantitative Trait Locus: address of a gene Ex: 6p24.q2 P-short arm Q-long arm 5.2 Mitosis and Cytokinesis

16. Sex chromosomes – determine the sex of an organism Sex chromosomes, X and Y, determine gender in mammals. May also carry genes for other characteristics 2 sex chromosomes Normal Females XX Normal males XY Autosomes – all of the other chromosomes 44 autosomes Two sets of each autosome Receive one copy of an autosome from each parent 6.1 Chromosomes and Meiosis

17. Homologous - pairs of autosomes – have the same size and shape and carry genes for the same traits Karyotype – photomicrograph of chromosomes in a dividing cell 6.1 Chromosomes and Meiosis

19. Chromosomes contain many genes. –The farther apart two genes are located on a chromosome, the more likely they are not to be inherited together –Genes located close together on a chromosome tend to be inherited together - genetic linkage. allows the distance between two genes to be calculated. 6.6 Meiosis and Genetic Variation