Transcript Unit 5 - Perry Local Schools

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
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
5.5 Multicellular Life
Stem cells
• 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
1. Totipotent - grow into any other cell type including another
stem cell
2. Pluripotent - grow into any cell type but a totipotent cell
3. 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.
Stem Cell Tracheal Transplant
Saves Girl's Life
• http://www.youtube.com/watch?v=WopEQ
1gHZIQ
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
5.2 Mitosis and Cytokinesis
Anatomy of a Chromosome
Telomere
Telomere
Centromere
Telomere
Telomere
Chromatid
Chromatid
Chromosome
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
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)
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
n
Haploid
Gamete
+
+
+
+
Egg cell
n
Haploid
Gamete
=
=
=
=
Fertilized Egg
2n
Diploid
Zygote