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

2. 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

3. 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

4. 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. 5.5 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

6. 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.

7. 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.

8. 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

9. 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

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

11. 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

12. 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

14. 5.2 Mitosis and Cytokinesis
P-short arm
QTL – Quantitative Trait Locus: address of a gene
Ex: 6p24.q2
Q-long arm

15. 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.

16. 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)

17. 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.

18. 6.1 Chromosomes and Meiosis
Gametes are haploid.
Haploid (n) cells have one copy of every chromosome.
Human n = 23

19. 6.1 Chromosomes and Meiosis
Sperm cell + Egg cell = Fertilized Egg
n n = 2n
Haploid + Haploid = Diploid
Gamete + Gamete = Zygote