KEY CONCEPT Cells work together to carry out complex functions. 5.5 Multicellular Life.
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Transcript of KEY CONCEPT Cells work together to carry out complex functions. 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
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
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 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
5.5 Multicellular Life
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.– The use of adult stem cells may prevent transplant
rejection.– The use of embryonic
stem cells raisesethical issues
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.
5.5 Multicellular Life
KEY CONCEPT Gametes have half the number of chromosomes that body cells have.
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)
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
6.1 Chromosomes and Meiosis
• Haploid (n) cells have one copy of every chromosome.
Human n = 23
6.1 Chromosomes and MeiosisGametes are haploid.
n (sperm cell) + n (egg cell) =2n (fertilized egg)
Haploid + Haploid = Diploid
Gamete + Gamete = Zygote
6.1 Chromosomes and Meiosis
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 doublehelix
DNA andhistones
Chromatin SupercoiledDNA
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
5.2 Mitosis and Cytokinesis
Anatomy of a Chromosome
XTelomere
Telomere
Centromere
Chromatid Chromatid
Telomere
Telomere
Chromosome
5.2 Mitosis and Cytokinesis
QTL – Quantitative Trait Locus: address of a geneEx: 6p24.q2
P-short arm
Q-long arm
5.2 Mitosis and Cytokinesis
• 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.
6.6 Meiosis and Genetic Variation
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
• 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
6.1 Chromosomes and Meiosis