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Download 7) NATURAL SELECTION: the process by which forms of life having
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7) NATURAL SELECTION: the process by which forms of life having traits that better fit a specific environmental pressure, such as predators, changes in climate, or competition for food or mates, will tend to survive and reproduce in greater numbers than others of their kind, thus ensuring the continuance of those favorable traits in succeeding generations. 8) CHROMOSOME: Threadlike strands of DNA and protein located in the cell’s nucleus; they carry the gene codes 9) GENE: The basic unit of heredity carried by the chromosomes; composed of two paired alleles; it codes for features or traits of organism. FEATURE: structure, characteristic, or behaviorinofanan TRAIT: AAspecific way a feature is expressed organism, such as eye color, fur pattern, or timing of individual organism. migration. TRAIT: A specific way a feature is expressed in an individual organism. Trait: some zebras know how to ride a motorcycle to escape predators Table of Contents (the TOC) Unit 2, Population Diversity Date 10/ 10/27 Description Pg # Features and Traits 1 Genetics 2 Inside the nucleus is the inheritance messenger, DNA. (Deoxyribonucleic acid). DNA molecules are “huge” containing millions of atoms. In order to fit inside the nucleus, they are coiled and coiled again into structures called CHROMOSOMES - the ______________ structures that carry the message of inheritance. This drawing shows the nucleus of a cell from our animal, the larkey. Notice that there are eight chromosomes, looking a little bit like bent hot dogs of different lengths. If you look closely, you will see that these two chromosomes are the same, these two are the same, and so on. Chromosomes always come in pairs. So our larkey actually has four pairs of chromosomes rather than eight different ones. Now look at the dark areas. Both chromosomes in a pair have dark areas exactly the same location. The dark areas are called alleles. Note: Alleles are not really dark. The dark color is used to represent the location of the alleles on the chromosomes The two alleles on the paired chromosomes work together. Together they constitute a gene. Summary • Nuclei contain chromosomes. • Chromosomes come in almost identical pairs. • Chromosomes have specific active locations called alleles. • The two alleles in identical locations on paired chromosomes constitute a gene A gene (two alleles working together) controls a trait. This gene could be the one that determines the larkey’s eye color, or perhaps the pattern of its fur. Let’s say it determines eye color. The larkey has four features of interest to us. Each feature is controlled by one gene. Each of the four genes is on a different chromosome (although they could have all been on the same chromosome). The gene location for appendages (legs) is these two alleles on this pair of chromosomes. The alleles are labeled with the letter A for appendages. Find the gene locations for eye color (letter E), fur pattern (letter F), and tail shape (T). Notice that some of the alleles are labeled with uppercase letter and some are lowercase letters. Both upper and lowercase letter Es are alleles for eye color. Alleles don’t all have equal influence in determining traits. Moreinfluential alleles are dominant alleles, and they are represented by an uppercase letter. Less-influential alleles are called recessive alleles, and they are represented by a lowercase letter. The alleles are the code that determines the traits of the larkeys. The chart at the bottom is the genetic code for one of the 32 larkeys we viewed previously. The alleles for legs is aa, eye color = Ee, fur pattern = FF, and tail shape = tt; The alleles for legs is aa, eye color = Ee, fur pattern = FF, and tail shape = tt; The combination of alleles in an organism's chromosomes is the organism’s genotype. The genotype lists the paired alleles that are particular to that organism. Let’s look at the genotype of our larkey to see what is dominant and what is recessive. • Two recessive alleles for leg length (aa) • One dominant and one recessive allele for eye color (Ee) • Two dominant alleles for fur pattern (FF) • Two recessive alleles for tail shape (tt). Let’s look at the genotype of our larkey to see what is dominant and what is recessive. • Two recessive alleles for leg length (aa) • One dominant and one recessive allele for eye color (Ee) • Two dominant alleles for fur pattern (FF) • Two recessive alleles for tail shape (tt). The parents of a Larkey both have red eyes. Is it possible for them to produce an offspring with grey eyes? In your notebook use a Punnet Square to prove or disprove this grey eye question. (The alleles for eyes are E or e.) The parents of a Larkey both have red eyes. Is it possible for them to produce an offspring with grey eyes? In your notebook use a Punnet Square to prove or disprove this grey eye question. (The alleles for eyes are E or e.) Female Ee E Male Ee e E E E E e E e e e e WORD BANK (top) chromosomes (2x) dominant, DNA, genes, genotype, nucleus, paired alleles, phenotype, recessive; WORD BANK (bottom) allele, chromosome, gene, nucleus. Top (in order) nucleus, DNA, chromosomes, Chromosomes, genes, paired alleles, genotype, phenotype, dominant, recessive. Bottom (in order) chromosome, gene, nucleus, allele Survival of the fittest Peppered Moth example, an adult giraffe grows a longer neck because it has difficulty reaching the leaves in its ecosystem