Slide 1:Chapter 5: Heredity


Slide 2: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. Genetics


Slide 3:Inheriting Traits Heredity (huh REH duh tee) is the passing of traits from parent to offspring. Genetics


Slide 4:What is genetics? Generally, genes on chromosomes control the traits that show up in an organism. The different forms of a trait that a gene may have are called alleles (uh LEELZ). When a pair of chromosomes separates during meiosis (mi OH sus), alleles for each trait also separate into different sex cells. Genetics


Slide 5:What is genetics? Every sex cell has one allele for each trait. The study of how traits are inherited through the interactions of alleles is the science of genetics (juh NE tihks). Genetics


Slide 6:Mendel—The Father of Genetics Gregor Mendel began experimenting with garden peas in 1856. Mendel made careful use of scientific methods, which resulted in the first recorded study of how traits pass from one generation to the next. Genetics


Slide 7:Mendel——The Father of Genetics He was also the first to use the mathematics of probability to explain heredity. Genetics Mendel was the first to trace one trait through several generations.


Slide 8: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 (HI brudz) because they received different genetic information, or different alleles, for a trait from each parent. Genetics


Slide 9:Genetics in a Garden An organism that always produces the same traits generation after generation is called a purebred. Genetics


Slide 10:Genetics in a Garden Tall plants that always produce seeds that produce tall plants are purebred for the trait of tall height. Genetics


Slide 11:Dominant and Recessive Factors In his experiments, Mendel used pollen from the flowers of purebred tall plants to pollinate by hand the flowers of purebred short plants. This process is called cross-pollination. Genetics


Slide 12:Dominant and Recessive Factors He found that tall plants crossed with short plants produced seed that produced all tall plants. Genetics


Slide 13:Dominant and Recessive Factors Mendel called the tall form the dominant (DAH muh nunt) factor because it dominated, or covered up, the short form. Genetics He called the form that seemed to disappear the recessive (rih SE sihv) factor.


Slide 14:Using Probability to Make Predictions Probability is a branch of mathematics that helps you predict the chance that something will happen. Genetics


Slide 15:Using Probability to Make Predictions Mendel also dealt with probabilities. Genetics One of the things that made his predictions accurate was that he worked with large numbers of plants. He studied almost 30,000 pea plants over a period of eight years. By doing so, Mendel increased his chances of seeing a repeatable pattern.


Slide 16:Punnett Squares How could you predict what the offspring would look like without making the cross? Genetics A handy tool used to predict results in Mendelian genetics is the Punnett (PUH nut) square.


Slide 17:Punnett Squares In a Punnett square, letters represent dominant and recessive alleles. Genetics


Slide 18:Punnett Squares Genetics An uppercase letter stands for a dominant allele. A lowercase letter stands for a recessive allele.


Slide 19:Punnett Squares They show the genotype (JEE nuh tipe), or genetic makeup, of an organism. Genetics The way an organism looks and behaves as a result of its genotype is its phenotype (FEE nuh tipe).


Slide 20:Alleles Determine Traits Most cells in your body have two alleles for every trait. Genetics These alleles are located on chromosomes within the nucleus of cells. Example: Trait – Height T allele would be for Tall t allele would be for short


Slide 21:Alleles Determine Traits An organism with two alleles that are the same is called homozygous (hoh muh ZI gus). Example: TT Genetics An organism that has two different alleles for a trait is called heterozygous (he tuh roh ZI gus). Example: Tt


Slide 22:Making a Punnett Square Genetics


Slide 23:Law of Dominance Law of Segregation Law of Independent Assortment Mendel’s Laws of Genetics


Slide 24:An allele’s effect is Dominant or Recessive More common traits tend to be dominant and less common are recessive. Example: Trait – Height T – Tall and t – short TT would be: Tall Tt still would be: Tall (The big T is dominant) tt would be: Short Law of Dominance


Slide 26:Each parent gives one and only one allele, or part of a gene pair, to an egg or sperm. When fertilization occurs, the offspring’s gene pair is determined by which allele each sex cell carried. Law of Segregation


Slide 28:The pair of alleles for each trait is passed on to offspring independently of one another. This means that the offspring can have combinations of genes that neither parent has. So, the offspring can look differently than both parents. Example: The inheritance of seed color has no effect on the inheritance of seed pod color. Law of Independent Assortment


Slide 31:Sex Determination 1. Chromosomes that determine the sex of an organism are XX in girls and XY in males. Genetics Since Mendel 2. Females produce eggs with X chromosomes only. Males produce sperm with X and Y chromosomes.


Slide 32:Genetics Since Mendel


Slide 33:Sex-Linked Disorders 1. An allele inherited on a sex chromosome is called a sex-linked gene. Genetics Since Mendel 2. Color blindness is a sex-linked disorder in which people cannot distinguish between certain colors, particularly red and green.


Slide 34:Sex-Linked Disorders This trait is a recessive allele on the X chromosome. Genetics Since Mendel Because males have only one X chromosome, a male with this allele on his X chromosome is color-blind. A color-blind female occurs only when both of her X chromosomes have the allele for this trait.


Slide 35:Pedigrees Trace Traits A pedigree is a visual tool for following a trait through generations of a family. Genetics Since Mendel Males are represented by squares and females by circles.


Slide 36:Pedigrees Trace Traits A completely filled circle or square shows that the trait is seen in that person. Genetics Since Mendel Half-colored circles or squares indicate carriers. People represented by empty circles or squares do not have the trait and are not carriers.


Genetics Problems :Genetics Problems Trait: Hair Color Brown – B Cross: Dad- Homozygous Dominant black – b x Mom – Heterozygous Dad ____________ x _____________Mom Genotypes: Phenotypes:


Genetics Problems :Genetics Problems 2. Trait: Eye Color Blue – g Cross: Dad- Heterozygous Green – G x Mom – Heterozygous Dad ____________ x _____________Mom Genotypes: Phenotypes:


Genetics Problems :Genetics Problems 3. Trait: Freckles No Freckles – F Cross: Dad- Heterozygous Freckles – f x Mom – Homozygous Recessive Dad ____________ x _____________Mom Genotypes: Phenotypes: