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

2. 5.5 Multicellular Life
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.
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 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

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

5. 5.5 Multicellular Life Stem cells are classified into 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

6. 5.5 Multicellular Life Stem cells come from adults and embryos.
Adult stem cells can be hard to isolate and grow.
The use of adult stem cells may prevent transplant rejection.
The use of 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 currently realized and potential benefits.
Stem cells are used to treat leukemia and lymphoma.
Stem cells may cure disease or replace damaged organs.
Stem cells may revolutionize the drug development process.

8. 6.1 Chromosomes and Meiosis
KEY CONCEPT Gametes have half the number of chromosomes that body cells have.

9. You have body cells and gametes.
6.1 Chromosomes and Meiosis
You have body cells and gametes.
Body cells are also called somatic cells.
Sex cells = Germ cells develop into gametes.
Germ cells are located in the ovaries and testes.
Gametes are sex cells: egg and sperm.
body cells
sex cells (sperm)
sex cells (egg)

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

11. 6.1 Chromosomes and Meiosis
Gametes are haploid.
Haploid (n) cells have one copy of every chromosome.
Human n = 23

12. 6.1 Chromosomes and Meiosis
n (sperm cell) + n (egg cell) =2n (fertilized egg)
Haploid + Haploid = Diploid
Gamete + Gamete = Zygote

13. 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

14. 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
To keep the chromosome from unwinding

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

16. 5.2 Mitosis and Cytokinesis
P-short arm
Q-long arm
QTL – Quantitative Trait Locus: address of a gene
Ex: 6p24.q2

17. Chromosomes contain many genes.
6.6 Meiosis and Genetic Variation
Chromosomes contain many genes.
The farther apart two genes are located on a chromosome, the more likely they are to be separated by crossing over.
Genes located close together on a chromosome tend to be inherited together, which is called genetic linkage.
Genetic linkage allows the distance between two genes to be calculated.

18. Sex chromosomes – determine the sex of an organism
6.1 Chromosomes and Meiosis
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

19. 6.1 Chromosomes and Meiosis
Your body cells have 23 pairs of chromosomes.
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