Genetics and Heredity PDF

# Genetics and Heredity ## Inheriting Traits * Eye color, nose shape, and many other physical features are some of the traits that are inherited from parents. * An organism is a collection of traits, all inherited from its parents. ## Vocabulary * **Heredity** - passing of traits from parent to...

# Genetics and Heredity ## Inheriting Traits * Eye color, nose shape, and many other physical features are some of the traits that are inherited from parents. * An organism is a collection of traits, all inherited from its parents. ## Vocabulary * **Heredity** - passing of traits from parent to offspring * **Genetics** - the study of traits passed from parents to offspring * **Trait** - genetically determined variant of a characteristic * **Trait vs. Characteristic** - if a characteristic is "eye color," **blue eyes** would be a possible trait. * **Alleles** - different forms of a trait ## Genetics * Every sex cell has one allele for each trait. * **Genetics** is the study of how traits are inherited through the interactions of alleles. ## Father of Genetics * **Gregor Mendel** began experimenting with garden peas in 1856. * He carefully observed the pea plants, resulting in the first recorded study of how traits pass from one generation to the next. * He used the math of probability to explain heredity. * He was the first to trace one trait through several generations. ## Genetics in a Garden * Each time Mendel studied a trait, he crossed two plants with different expressions of the trait and found that the new plants all looked like one of the two parents. * He called these new plants **hybrids** because they received different genetic information or different alleles for a trait from each parent. | Traits | Shape of Seeds | Color of Seeds | Color of Pods | Shape of Pods | Plant Height | Position of Flowers | Flower Color | |---|---|---|---|---|---|---|---| | Dominant Trait | Round | Yellow | Green | Full | Tall | At leaf junctions | Purple | | Recessive Trait | Wrinkled | Green | Yellow | Flat, Constricted | Short | At tips of branches | White | * **Purebred** - an organism that always produces the same traits generation after generation. * Ex. Tall plants that always produce seeds that produce tall plants are purebred for the trait of tall height. * **Self-pollination** - when pollen from a plant is transferred to a flower on the same plant. * **Cross pollination** - when pollen from a plant is transferred to a flower on a different plant. * In his experiments, Mendel used pollen from the flowers of purebred tall plants to pollinate by hand the flowers of purebred short plants. ## Dominant vs. Recessive * Mendel found that tall plants crossed with short plants produced all tall plants. * **DOMINANT vs. RECESSIVE** * **Dominant** - Mendel called the tall form dominant because it dominated, or covered up, the short form. * **Recessive** - he called the form that seemed to disappear the recessive factor. ## Probability - Make a Prediction * Mendel used probability (a branch of math that helps you predict the chance that something will happen). * His predictions were accurate because he worked with a large number of plants (almost 30,000 pea plants in 8 years) thereby increasing his chances of seeing a repeatable pattern. ## Punnett Squares * A tool used to predict results in genetics is the **Punnett square**. It helps you predict what offspring would look like. * In a Punnett square, letters represent dominant and recessive alleles. * An uppercase letter stands for a dominant allele. * A lowercase letter stands for a recessive allele. * Punnett squares show the **genotype** or the genetic makeup of an organism inherited from its parents. * It also shows the **phenotype**, which is the appearance of an organism (ex. Tall or short). ## Homozygous vs. Heterozygous * Most cells in your body have two alleles for every trait. The alleles are located on chromosomes within the nucleus. * **Ex. Trait - Height** * **T allele would be for Tall** * **t allele would be for short** * An organism with two alleles that are the same is called **homozygous**. Ex. TT * An organism that has two different alleles for a trait is called **heterozygous**. Example Tt. ## Making a Punnett Square | | B | B | |---|:---:|:---:| | b | Bb | Bb | | b | Bb | Bb | ## Dominance * An allele's effect is Dominant or recessive. * More common traits tend to be dominant and less common are recessive. * Ex. T – Tall, t – short * TT would be Tall * Tt would still be Tall (because big T is dominant) * tt would be short ## Diagram of pea plant pollination cross * **Pollen** (Male) - B, b * **Pistil** (Female) - B, b <start_of_image> ดอกไม้ B b B BB Bb b Bb bb ดอกไม้