Chapter 4: “The nucleus controls the functions of...
Transcript of Chapter 4: “The nucleus controls the functions of...
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Chapter 4: “The nucleus controls the functions of life.”
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the organelle that is responsible for heredity and for controlling the functions of the cell.the control centre of the cell
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The nucleus contains the master set of instructions that determines what each cell will become, how it will function, when it will grow and divide and when it will die.
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Trait: a particular feature that can vary in size or form from individual to individual within a species.Inherited from biological parents.
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Heredity: the process through which patterns of traits are passed on from an individual to its offspring.
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Carries the instructions in the nucleus.A long, double-stranded moleculeForms a helix structure (a twisted ladder).
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The DNA Molecule
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The sides of the DNA ladder are made of sugar and phosphate.The steps are made up of four nitrogen bases.
1. adenine (A)2. guanine (G)3. cytosine (C)4. thymine (T)
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The bases in a DNA molecule always join in a specific way:
A always joins with T
G always joins with C
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When a cell is ready to divide, each strand of loosely coiled DNA folds up further into a compact, X-shaped structure called a chromosome.
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Chromosomes within the nucleus are found in pairs.
Most humans have 23 pairs of chromosomes including one pair that determines gender.
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found on chromosomes.small segments of DNA located at specific places on a chromosome.store information needed to produce proteins used by body cells.
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Genes can vary in length from hundreds to thousands of bases.The arrangement of bases will determine the protein produced.Each chromosome contains thousands of
genes.
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Proteins determine what body cells will become and how they will function.
Specialize cells will form tissues; tissues will form organs.
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Specialized proteins called enzymes speed up the hundreds of chemical reactions that occur within each cell.
Ex. Digestive enzymes
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Some proteins act as chemical messengers called hormones.
Ex. Growth hormone
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A gene mutation is a change in the specific order of the bases that make up a particular gene.
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A base may be:
Added
Deleted
Substituted for another
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1. Positive Mutation
Benefits an individual
Ex. Resistance to disease
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2. Negative Mutation
Harms the individual
Reduce the probability that the individual will produce offspring or survive in their environment.
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Ex. Sickle cell anemia
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Ex. Cystic Fibrosis
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3. Neutral Mutation
Does not affect the individual
Ex. Coat Color
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Substances or factors that can cause mutations in DNA.
Ex. Cigarette smoke,
X-rays, pollutants
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Nature Ex. Solar radiation
Radioactive gasesHuman Activity
Ex. ChemicalsNuclear Radiation