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5.5 Multicellular Life KEY CONCEPT Cells work together to carry out complex functions.
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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
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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
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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
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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
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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.
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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.
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6.1 Chromosomes and Meiosis
KEY CONCEPT Gametes have half the number of chromosomes that body cells have.
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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)
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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
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6.1 Chromosomes and Meiosis
Gametes are haploid. Haploid (n) cells have one copy of every chromosome. Human n = 23
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6.1 Chromosomes and Meiosis
n (sperm cell) + n (egg cell) =2n (fertilized egg) Haploid + Haploid = Diploid Gamete + Gamete = Zygote
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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
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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
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Anatomy of a Chromosome
5.2 Mitosis and Cytokinesis Anatomy of a Chromosome X Telomere Telomere Centromere Telomere Telomere Chromatid Chromatid Chromosome
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5.2 Mitosis and Cytokinesis
P-short arm Q-long arm QTL – Quantitative Trait Locus: address of a gene Ex: 6p24.q2
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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.
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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
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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
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