Genetics PDF

GENETICS Lesson 1  Branch of biology concerned with the study of GENETICS Genes. its VARIATION and HEREDITY. Basic unit of Heredity. GENE sequence of nucleotides in DNA and RNA. Diversity, differences between individuals or VARIATION population....

GENETICS Lesson 1  Branch of biology concerned with the study of GENETICS Genes. its VARIATION and HEREDITY. Basic unit of Heredity. GENE sequence of nucleotides in DNA and RNA. Diversity, differences between individuals or VARIATION population. Genetic heritage passed down by our biological HEREDITY parents.  UNDERSTANDING DNA Chromosomes Gene DNA ( DEOXYRIBONUCLEIC ACID) IS A MOLECULE COMPOSED OF TWO POLYNUCLEOTIDE CHAINS THAT COIL AROUND EACH OTHER TO FORM A DOUBLE HELIX CARRYING GENETIC INSTRUCTIONS FOR THE DEVELOPMENT, FUNCTIONING, GROWTH AND REPRODUCTION OF ALL KNOWN ORGANISMS AND MANY VIRUSES. DNA ( DEOXYRIBONUCLEIC ACID) TYPES OF BASES ADENINE THYMINE CYTOSINE GUANINE SEQUENCE OF THE BASES ARE ACTUALLY THE CODES FOR TRAITS.  CHROMOSOMES CHROMOSOMES ARE THREAD-LIKE STRUCTURES LOCATED INSIDE THE NUCLEUS OF ANIMAL AND PLANT CELLS. EACH CHROMOSOME IS MADE OF PROTEIN AND A SINGLE MOLECULE OF DEOXYRIBONUCLEIC ACID (DNA). CHROMOSOMES  GENE A GENE IS A BASIC UNIT OF HEREDITY AND A SEQUENCE OF NUCLEOTIDES IN DNA OR RNA. TRAITS ARE USUALLY FOUND HERE FATHER OF GENETICS Gregor Johann Mendel was a monk and teacher with interests in astronomy and plant breeding. He was born in 1822, and at 21, he joined a monastery in Brünn (now in the Czech Republic). The monastery had a botanical garden and library and was a centre for science, religion and culture. In 1856, Mendel began a series of experiments at the monastery to find out how traits are passed from generation to generation. At the time, it was thought that parents’ traits were blended together in their progeny. Mendel is known as the father of genetics because of his ground-breaking work on inheritance in pea plants 150 years ago. GREGOR MENDEL  IMPORTANT TERMS & THINGS TO REMEMBER Allele - An allele is one of a pair of genes that appear at a particular location on a particular chromosome and control the same characteristic, such as blood type or color blindness. usually these are the copies of chromosomes from the biological parents. Allele or Traits are usually represented by letters. Capital letters indicates Dominant trait and Small letters indicates recessive traits. Dominant Trait - Trait that first appears or is visibly expressed in an organism Recessive Trait - Trait that is masked and does not show itself in the organism. Genotype-Combination of alleles an organism inherit from parent (Genetic code) Phenotype - The Physical Apperance of traits in an organism. Traits of pea plants Mendel followed the inheritance of 7 traits in pea plants, and each trait had 2 forms. He identified pure- breeding pea plants that consistently showed 1 form of a trait after generations of self-pollination. Mendel described each of the trait variants as dominant or recessive traits, like purple flower colour, appeared in the F1 hybrids, whereas recessive traits, like white flower colour, did not. Mendel did thousands of cross-breeding experiments. His key finding was that there were 3 times as many dominant as recessive traits in F2 pea plants (3:1 ratio). Punnett Square - Method used to determine the probabilities of Offspring.  Mendel's Law of Heredity 1) The Law of Segregation: Each inherited trait is defined by a gene pair. Parental genes are randomly separated to the sex cells so that sex cells contain only one gene of the pair. Offspring therefore inherit one genetic allele from each parent when sex cells unite in fertilization. 2) The Law of Independent Assortment: Genes for different traits are sorted separately from one another so that the inheritance of one trait is not dependent on the inheritance of another. 3) The Law of Dominance: an organism with alternate forms of a gene will express the form that is dominant. The Law of Independent Assortment: Genes for different traits are sorted separately from one another so that the inheritance of one trait is not dependent on the inheritance of another.  The Law of Dominance: an organism with alternate forms of a gene will express the form that is dominant. Complete Dominance - occurs when one allele or “version” of a gene completely masks another. The trait that is expressed is described as being “dominant” over the trait that is not expressed.  Incomplete Dominance - It refers to a circumstance in which the two copies of a gene for a particular trait, or alleles, combine so that neither dominates the other. This creates a new phenotype or set of observable characteristics caused by the interaction of genetics and environment. In short, incomplete dominance is when neither gene is fully dominant, and the result is a brand new trait. Codominance- is a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele usually will be expressed, while the effect of the other allele, called recessive, is masked. In codominance, however, neither allele is recessive and the phenotypes of both alleles are expressed.