Lesson 2 Genetics PDF

Introduction to GENETICS  LEARNING TARGETS I CAN... 1. Describe the different Mendelian Laws of Inheritance. 2. Illustrate the process to predict the genotypes and phenotypes of offspring.  PRELIMINARY ACTIVITY: CHECK ON YOUR SEATMATE!  1. Ability to roll tongue 2. Deta...

Introduction to GENETICS  LEARNING TARGETS I CAN... 1. Describe the different Mendelian Laws of Inheritance. 2. Illustrate the process to predict the genotypes and phenotypes of offspring.  PRELIMINARY ACTIVITY: CHECK ON YOUR SEATMATE!  1. Ability to roll tongue 2. Detached or attached earlobes 3. Straight hair line or widow’s peak 4. With dimples or without dimples INTRODUCTION TO GENETICS  what is genetics? the scientific study of genes and heredity, or how variations in DNA sequence cause specific characteristics or traits to be passed from parents to offspring. the branch of biology concerned with the study of the DNA of organisms, how their DNA manifests as genes, and how those genes are inherited by offspring. GENETICS The scientific study of genes and how they affect the heredity. GENES Units of heredity composed of DNA molecules that are transferred from parents to their offspring.  gene considered the basic unit of inheritance passed from parents to offspring and contain the information needed to specify physical and biological traits part of our genome that encodes the information for making those code for specific proteins, or segments of proteins human genome has roughly 20,000 protein-coding genes made up of DNA (deoxyribonucleic acid)  dna mostly located in the cell nucleus (where it is called nuclear DNA) information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). base pairs: A with T and C with G each base is also attached to a sugar molecule and a phosphate molecule.  DNA backbone is composed of alternating deoxyribose sugar and phosphate Based Erwin Chargaff, an Austrian biochemist, the percentage of adenine is always equal to thymine, and the percentage of guanine is always equal to cytosine.  DNA a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix. IMPORTANT TERMS TO REMEMBER IMPORTANT TERMS TO REMEMBER brief history of genetics Father of Genetics - Gregor Mendel The genetic experiments Mendel did with pea plants took him eight years (1856- 1863), and he published his results in 1865. During this time, Mendel grew over 10,000 pea plants, keeping track of progeny number and type. CHARACTERISTICS OF GARDEN PEAS STUDIED BY MENDEL GREGOR JOHANN MENDEL his experiment led to the formulation of the laws of inheritance, which includes: a. Law of Dominance b. Law of Segregation c. Law of Independent Assortment LAW OF DOMINANCE? LAW OF SEGREGATION? LAW OF INDEPENDENT ASSORTMENT? What does the picture indicate?  LAW OF SEGREGATION individual has a pair of alleles for each trait. the alleles in the pair separate, such that each gamete receives only one allele for the trait Each parent passes an allele at random to the offspring. It is only upon gamete formation that the alleles are segregated. LAW OF DOMINANCE? LAW OF SEGREGATION? LAW OF INDEPENDENT ASSORTMENT? What does the picture indicate? LAW OF INDEPENDENT ASSORTMENT States that alleles segregate independently during the formation of gametes. The genes do not influence one another on how they are sorted. This law can be represented by Mendel’s dihybrid experiment. LAW OF INDEPENDENT ASSORTMENT LAW OF DOMINANCE? LAW OF SEGREGATION? LAW OF INDEPENDENT ASSORTMENT? What does the picture indicate?  LAW OF DOMINANCE A trait is said to be dominant if it is expressed in spite of the presence of another allele. it states that some alleles are dominant, whereas others are recessive. An organism with a dominant allele for a certain trait. will always express that trait.  LAW OF DOMINANCE However, an organism with a recessive allele for a particular trait will express that trait only if the dominant allele is not present LET’S PUT INTO PRACTICE! MENDELIAN LAWS THROUGH PUNNETT SQUARE Punnett Square/Monohybrid Cross - a square divided into four quadrants Possible gene combinations are inside. Dominant alleles are represented by capital letters, while recessive alleles are lowercase letters. MONOHYBRID CROSS a cross between parents that may differ in one trait. each square signifies 25% chance of the genotype and phenotype of the offspring EXAMPLE the allele that codes for a yellow-colored flower (Y) is dominant over the allele that codes for a green-colored flower (y). Both parents (represented on top and on the left side of the square) contain heterozygous alleles that code for a yellow-colored flower (Yy). EXAMPLE Genotypic ratio (GR) = 1 YY : 2 Yy : 1 yy or 1 : 2 : 1 Phenotypic ratio (PR) = 3 yellow : 1 green or 3 : 1 SAMPLE PROBLEM: 1. In pea plants, the allele for tall plants (T) is dominant over the allele for short plants (t). A heterozygous tall plant is crossed with a short plant. Using Punnett Square, determine the phenotypic and genotypic ratio.  DIHYBRID CROSS Two contrasting traits between parents can also be crossed to determine their offspring's genotype and phenotype. For example, each parent has two sets of genes containing alleles for hair color and eye color. For the hair color, the allele for black hair (A) is dominant over the allele for blonde hair (a). For the eye color, the allele for brown eyes (B) is dominant over the allele for blue eyes (b).  STEPS IN DOING DIHYBRID CROSS 1. Identify the genotypes of the parents. 2. Determine the possible gamete combinations. 3. Write the possible gamete combinations of the parents on the top and on the left side of the square. 4. Pair the gametes inside the boxes. 5. Write the phenotype on each box 6. Identify the genotypic and the phenotypic ratios SAMPLE PROBLEM 1. IDENTIFY THE GENOTYPES OF THE PARENTS. Father (AABb) – homozygous black hair (AA) and heterozygous brown eyes (Bb) Mother (Aabb) – heterozygous black hair (Aa) and homozygous blue eyes PRACTICE PROBLEMS  PROBLEM 1 A case about paternity was presented in court. The details say that Brown eyes (B) dominate over blue eyes (b). A child has brown eyes (genotype Bb), the mother has brown eyes but is heterozygous (genotype Bb), but the father also has blue eyes (bb). Is the child the biological child of the couple?  PROBLEM 2 A case about paternity was presented in court. The details say that Black hair (D) is dominant over blonde hair (d). A child has blonde hair (genotype dd). The mother has black hair but is heterozygous (genotype Dd), and the father has black hair as well, but homozygous (DD). Is the child the biological child of the couple?  PROBLEM 3 In mice, the ability to run normally is a dominant trait. Mice with this trait are called running mice (R). The recessive trait causes mice to run in circles only. Mice with this trait are called waltzing mice (r). Hair color is also inherited in mice. Black hair (B) is dominant over brown hair (b). Cross a heterozygous running, heterozygous black mouse with a homozygous running, homozygous black mouse  PROBLEM 4 In rabbits, fur color and ear length are inherited traits. The allele for black fur (B) is dominant over brown fur (b), and the allele for long ears (L) is dominant over short ears (l). A rabbit that is heterozygous for fur color and homozygous dominant for ear length is crossed with another rabbit that is homozygous recessive for fur color and heterozygous for ear length. Find the probability of their offspring.  PROBLEM 5 In pea plants, seed shape and seed color are two traits that follow Mendelian inheritance. The allele for round seeds (R) is dominant over wrinkled seeds (r), and the allele for yellow seeds (Y) is dominant over green seeds (y). A pea plant that is heterozygous for both traits is crossed with another pea plant that is also heterozygous for both traits. Determine the probable characteristics of their offspring.  LET’S APPLY IT! MENDELIAN LAWS ON DIFFERENT FIELD Instructions: Find a pair you have to work with. Choose one from the list of fields where genetics can be applied. Research on information associated with the chosen field. Create an infographic about the connection of genetics to your chosen field. Individually submit output on Schoology, Mendelian Laws on Real-life / Social Context 1. Health Care 2. Agriculture and Food Security 3. Conservation of Species 4. Forensic Science and Legal Issues 5. Evolutionary and Ancestral Studies 6. Education and Awareness GOOD WORK, EVERYONE! RESOURCE PAGE