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Genetics and Diversity II Pedigrees and Adaptations 1 S1-1-14 Explain the inheritance of sex-linked traits in humans and use a pedigree. S1-1-08 Investigate adaptations of plant and animal species which enhance reproductive success. Vocabulary & People Sex-linked Natural Selection Pedigree Adaptation Sex chromosome X carries genes that code for traits other than gender. Traits determined by genes on the X chromosome are called sex-linked traits. Hemophilia, colour-blindness, and baldness are three common examples x y x x • Inherits trait from mother • Inherited from either parent (give the X) • Phenotype always shows gene (no other allele to mask it) • Needs two alleles to show • Will pass to ALL daughters Sex-linked traits are more common in males recessive trait • One recessive allele: will not show the trait - but is a “carrier” Y Father = X XY Mother is a carrier Mother = XX ¼ color-blind male – 25% XX YX XX YX ½ disorder free – 50% ¼ female carrier – 25% Pedigree: diagram representing the phenotype history of a family. Genotypes can be determined by analyzing the trends of the pedigree Symbols: Male – square Female – circle Dominant trait – blank Recessive trait – filled A widow's peak hairline (W) is dominant over a straight hairline (w): What are the genotypes for each person in this family? Ww W? Ww ww ww Ww ww ww Ww Ww ww W? Natural selection is the gradual process of traits becoming more common in a population because the traits may improve reproductive success of organisms in an environment. (It is a key mechanism of evolution) Luck and timing has something to do with it too… Anything that gives you an advantage will help you pass that positive trait on to offspring disadvantage : no offspring “Only The Strong Survive” Adaptation: a naturally selected trait that enhances reproductive success. • Can be physical or behavioural How would big tail feathers make him more successful? How would they make him less successful? Examples of Adaptations Behavioural • caring for young • mating calls • dances • fighting Physical • colours / camouflage • size / shape • pheromones • multiple offspring Those best able to modify their behavior or those with positive mutations that improve their survival and reproductive success pass on these traits to future offspring Think of adaptations that have evolved to help an organism (including humans) survive its environment and reproduce. CAN YOU ANSWER THESE QUESTIONS? S1-1-14: What is a pedigree and how is it used to track inheritance of a trait? S1-1-08: What are some ways plants and animals improve their chance to reproduce? Vocabulary & People Sex-linked Natural Selection Pedigree Adaptation