Mendelian Genetics - Genetics of Heredity PDF

MENDELIAN GENETICS GENETICS PATRICK NUNEZ GENETICS A branch of biology that deals with the study of heredity. HEREDITY - IS A BIOLOGICAL PROCESS WHERE PARENTS PASSED CERTAIN GENES ONTO THEIR OFFSPRING. FERTILIZATION The union of sperm cell and egg cell to from zygote....

MENDELIAN GENETICS GENETICS PATRICK NUNEZ GENETICS A branch of biology that deals with the study of heredity. HEREDITY - IS A BIOLOGICAL PROCESS WHERE PARENTS PASSED CERTAIN GENES ONTO THEIR OFFSPRING. FERTILIZATION The union of sperm cell and egg cell to from zygote. 23 Chromosomes + 23 Chromosomes ZYGOTE 46 Chromosomes between TRAITS and CHARACTERISTIC S?  TRAIT is a general attribute of an individual while CHARACTERISTIC is a distinctive quality of a certain organism. TRAIT: COLOR OF HAIR CHARACTERISTICS: BLACK or BROWN TRAITS CAN BE DOMINANT or RECESSIVE  DOMINANT -These genes that masks the other genes. RECESSIVE These are genes that are masked or hidden by the dominant gene. TRAITS and CHARACTERISTICS are dictated by GENES. Let’s observe the traits in this room! Determine which is dominant and recessive  GENE - is a fundamental unit of heredity in living organisms. - Genes consist of DNA and are responsible for coding the instructions for building and maintaining cells and passing genetic information from one generation to the next. ALLELE - is a variant form of a gene that arises by mutation and is found at a specific place on a chromosome. - Alleles contribute to the genetic diversity within a population by introducing variations in traits.  DNA - A MATERIAL IN OUR CELLS’ NUCLEUS WHICH CHROMOSOMES - A THREAD-LIKE STRUCTURE WHICH HOLDS OUR GENETIC CODE FOR OUR BODY’S COMPOSED OF COILED DNA. INSTRUCTIONAL MANUAL. GENES - CONSIST OF DNA AND ARE RESPONSIBLE FOR ALLELES - CONTRIBUTE TO THE GENETIC DIVERSITY CODING THE INSTRUCTIONS FOR BUILDING AND WITHIN A POPULATION BY INTRODUCING VARIATIONS MAINTAINING CELLS AND PASSING GENETIC IN TRAITS. INFORMATION FROM ONE GENERATION TO THE NEXT. GENES CAN BE HOMOZYGOUS or HETEROZYGOUS  HOMOZYGOUS DOMINANT - BOTH DOMINANT ALLELE = DD) HOMOZYGOUS RECESSIVE - (BOTH RECESSIVE ALLELE = DD) HETEROZYGOUS - DIFFERENT ALLELES (DD) MENDELIA N GENETICS MENDELIAN INHERITANCE / MENDELISM GREGOR JOHANN MENDEL - he excelled in physics and mathematics, completing his studies in 1843. - As his father’s only son, Mendel was expected to take over the small family farm, but he preferred a different solution to his predicament, choosing to enter the Altbrünn monastery as a novitiate of the Augustinian order, where he was given the name Gregor. - As a priest, Mendel found his parish duty to visit the sick and dying so distressing that he again became ill. - However, in 1850 Mendel failed an exam— introduced through new legislation for teacher certification—and was sent to the University of Vienna for two years to benefit from a new program of scientific instruction. - Mendel chose to conduct his studies with the edible pea (Pisum sativum) because of the numerous distinct varieties, the ease of culture and control of pollination, and the high proportion of successful seed germinations. From 1854 to 1856 he tested 34 varieties for constancy of their traits. 7 DISTINCT TRAITS OF PEA PLANT (Pisum sativum) Gregor Mendel’s Pea Plant Experiment - In order to trace the transmission of characters, he chose seven traits that were expressed in a distinctive manner, such as plant height (short or tall) and seed color (green or yellow). - He crossed varieties that differed in one trait—for instance, tall crossed with short. - The first generation of hybrids (F1) displayed the character of one variety but not that of the other. In Mendel’s terms, one character was dominant and the other recessive. Gregor Mendel’s Pea Plant Experiment - In the numerous progeny that he raised from these hybrids (the second generation, F2), however, the recessive character reappeared, and the proportion of offspring bearing the dominant to offspring bearing the recessive was very close to a 3 to 1 ratio. - Study of the descendants (F3) of the dominant group showed that one-third of them were true-breeding and two-thirds were of hybrid constitution. - The 3:1 ratio could hence be rewritten as 1:2:1, meaning that 50 percent of the F2 generation were true-breeding and 50 percent were still hybrid. WHAT DID HE FOUND OUT? GENETICS continuation LAWS OF MENDELIAN INHERITANCE PATRICK NUÑEZ Law of Segregation of Genes - states that every individual organism contains two alleles for each trait, and that these alleles segregate (separate) during meiosis such that each gamete contains only one of the alleles. - An offspring thus receives a pair of alleles for a trait by inheriting homologous chromosomes from the parent organisms: one allele for each trait from each parent. Law of Dominance The presence of an allele does not mean that the trait will be expressed in the individual that possesses it. If the two alleles of an inherited pair differ (the heterozygous condition), then one determines the organism’s appearance and is called the dominant allele; the other has no noticeable effect on the organism’s appearance and is called the recessive allele. Thus, the dominant allele will hide the phenotypic effects of the recessive allele. Law of Independent Assortment States that alleles for separate traits are passed independently of one another. That is, the biological selection of an allele for one trait has nothing to do with the selection of an allele for any other trait. Mendel found support for this law in his dihybrid cross experiments. In his monohybrid crosses, an idealized 3:1 ratio between dominant and recessive phenotypes resulted. In dihybrid crosses, however, he found a 9:3:3:1 ratios. MONOHYBRID A TYPE OF PUNNETT SQUARE WHICH CROSSES 1 TRAIT ONLY. DIHYBRID A TYPE OF PUNNETT SQUARE WHICH CROSSES 2 TRAITS AT THE SAME TIME. DIHYBRID A TYPE OF PUNNETT SQUARE WHICH CROSSES 2 TRAITS AT THE SAME TIME. TRIHYBRID A TYPE OF PUNNETT SQUARE WHICH CROSSES 3 TRAITS AT THE SAME TIME.