5.5 Multicellular Life Cells work together to carry out complex functions

5.5 Multicellular Life Multicellular organisms depend on interactions among different cell types. Tissues - groups of cells that perform a similar function. Organs - groups of tissues that perform a specific or similar function. Organ systems - groups of organs that carry out similar functions. Cells  Tissues  Organs  Organ Systems CELL TISSUE ORGAN

Specialized cells perform specific functions. 5.5 Multicellular Life Specialized cells perform specific functions. Cells develop into their mature forms through the process of 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

Stem cells 5.5 Multicellular Life have the ability to divide and renew themselves and remain undifferentiated OR develop into a variety of specialized cell types

5.5 Multicellular Life 3 types of stem cells Totipotent - grow into any other cell type including another stem cell Pluripotent - grow into any cell type but a totipotent cell Multipotent - grow into cells of a closely related cell family

5.5 Multicellular Life 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 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.

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

Chromosome – rod-shaped structures made of DNA & protein 5.2 Mitosis and Cytokinesis 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 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

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

Sex chromosomes – determine the sex of an organism 6.1 Chromosomes and Meiosis Sex chromosomes – determine the sex of an organism X and Y 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 Receive one copy of an autosome from each parent

6.1 Chromosomes and Meiosis Homologous - pairs of autosomes One from each parent have the same size and shape and carry genes for the same traits Karyotype – photomicrograph of chromosomes in a dividing cell Determine sex of individual Determine any chromosomal abnormalities

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

Chromosomes contain many genes. 6.6 Meiosis and Genetic Variation Chromosomes contain many genes. Genes located close together on a chromosome tend to be inherited together - genetic linkage. allows the distance between two genes to be calculated.

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

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

6.1 Chromosomes and Meiosis Sperm cell + Egg cell = Fertilized Egg n + n = 2n Haploid + Haploid = Diploid Gamete + Gamete = Zygote