Introduction to Genetics PDF

CHAPTER I: INTRODUCTION TO GENETICS GENETICS ❖ Branch of biology that deals with genes, heredity, and variations of organisms. HEREDITY ❖ AKA Inheritance ❖ Passing on of traits from parents to their offspring; either through asexual or sexual production ❖ Th...

CHAPTER I: INTRODUCTION TO GENETICS GENETICS ❖ Branch of biology that deals with genes, heredity, and variations of organisms. HEREDITY ❖ AKA Inheritance ❖ Passing on of traits from parents to their offspring; either through asexual or sexual production ❖ The offspring cells or organisms acquire the genetic information of their parents VARIATION ❖ Differences in genetic traits (both genotypic and phenotypic terms) among individuals of the same species GENETIC/GENOTYPIC VARIATION ❖ Differences between organisms caused by GENES alternate forms of DNA ❖ Basic unit of heredity ❖ Differences in the DNA make-up of each ❖ Consists of a sequence of nucleotides in organism DNA or RNA that encodes the synthesis of PHENOTYPIC VARIATION a gene product, either RNA or protein ❖ Differences that we see outside of the ❖ A segment of a DNA organisms ❖ Physical traits that we see on each GENE EXPRESSION AND PROTEIN organism SYNTHESIS ❖ Genetic variation in combination with environmental variation causes the total phenotypic variation seen in a population THE GENETIC MATERIAL All these variations and heredity happens because of the genetic material that makes up an organism LEVELS OF STRUCTURAL ORGANIZATION Organism  Organs PARTS OF THE DNA (Double helix)  Tissues  Cell  Chemicals (Molecular level) ❖ Sugar-Phosphate Backbone  ❖ Nitrogenous Bases (Guanine, Cytosine, ❖ Enzyme is now ready to make a strand of Thymine, Adenine) mRNA with a complementary sequence of ❖ Base Pairs (G with C, C with G, T with A, A bases with T) bound by a Hydrogen bond (H- STEP 2: ELONGATION bond) ❖ Addition of nucleotides to the mRNA STEPS IN GENE EXPRESSION strand ❖ Transcription ❖ RNA polymerase reads the unwound DNA ❖ Translation strand and builds the mRNA molecule TRANSCRIPTION using complementary base pairs ❖ In a brief time during this process, when the newly formed RNA is bound to the unwound DNA, an adenine (A) in the DNA binds to an uracil (U) in the RNA STEP 3: TERMINATION ❖ Occurs when RNA polymerase crosses a stop (termination) sequence in the gene ❖ The mRNA strand is complete and it detaches from DNA ❖ DNA winds back to its double helix form TRANSLATION (PROTEIN SYNTHESIS) ❖ Takes place in the nucleus ❖ Uses DNA as a template to make an RNA (mRNA) molecule ❖ By product: mRNA (messenger RNA) ❖ Process needs to be correct; if the complementary base added does not match, the process needs to start again ❖ If it does not start again, it could lead to cancer STEP 1: INITIATION ❖ Occurs when the enzyme RNA polymerase ❖ Same process with transcription binds to a region of a gene called the ❖ By product: Polypeptide chain promoter (located before the gene that STEP 1: INITIATION needs to be transcribed) ❖ mRNA exits the nucleus, enters the ❖ This signals the DNA to unwind so the cytoplasm, and binds to a ribosome enzyme can "read” the bases in one of the ❖ The ribosome reads the mRNA in sets of 3 DNA strands nucleotides/bases called Codons from 5’ to 3’ STEP 2: ELONGATION ❖ Blood type – the glycoproteins present on ❖ tRNA comes in with Anticodon the surface of RBC’s determines blood type (complementary bases of codons) located ❖ Lactose Intolerant – lack of gene to code on one end of the structure for the protein lactase (digests lactose) ❖ On the other end, tRNA carries amino SUMMARY acids (AA) ❖ These AA’s will be attached to each other to form a polypeptide chain STEP 3: TERMINATION ❖ Occurs when a stop codon enters the “acceptor” (A) site of the ribosome CODON TABLE ❖ Gene expression is a multi-step process starting from DNA transcription to RNA followed by translation into a protein which then folds and is modified to become functionally active PROTEIN FOLDING AND POST- HISTORY OF GENETICS TRANSLATIONAL MODIFICATIONS INHERITANCE ❖ People have known about inheritance for a long time (through detailed observation on their environment) Children resemble their parents Domestication of animals and plants, selective breeding for good ❖ The polypeptide chain would be modified characteristics suggests prehistoric by the golgi complex to become a people recognized concept of heredity functional protein through a process of Sumerian horse breeding records Proteolysis, Glycosylation, and Egyptian date palm breeding Phosphorylation DISPROVING OLD IDEAS ❖ These functional proteins will be Despite knowing about inheritance in general, a expressed by our body as our “traits” number of incorrect ideas had to be generated and EXAMPLE OF GENE EXPRESSION overcome before modern genetics could arise: ❖ Eye and Skin color – Melanin 1. Living organisms can be generated from ❖ Hair color and type – Keratin non-living material ❖ Muscle mass and strength – Actin & ❖ FACT: All life comes from other life. Myosin Living organisms are not  spontaneously generated from non- living material. 2. Monstrous hybrids exist and can be made ❖ FACT: They don’t. Species concept: offspring arise only when two members of the same species mate. 3. Preformation: In each sperm (or egg) is a tiny (miniature), fully-formed human that merely grows in size ❖ FACT: Organisms develop by 2. CYTOGENETICS expressing information carried in their ❖ Both the study of the structure of hereditary material. chromosome material and the study of 4. Ancient Greek idea: female is merely a diseases caused by structural and vessel during procreation; alleged New numerical abnormalities of chromosomes Guinea belief: sex is not related to ❖ Karyotype – the complete set of reproduction chromosomes in a species or in an ❖ FACT: Male and female parents individual organism contribute equally to the offspring via – Attention is paid to their length, the the gametes (sperm or egg cells) that position of the centromeres, banding each reproduce. Also, fertilization pattern, any differences between the occurs to the fetus that would become sex chromosomes, and any other the offspring of the parents. physical characteristics – Helps to see the abnormalities of the BRANCHES OF GENETICS chromosomes of an individual 1. TRANSMISSION GENETICS ❖ Includes the study of mode of gene transmission from generation to generation ❖ The kind of studies that Gregor Mendel performed are included in this discipline ❖ Example of Genetic abnormality: – Klinefelter Syndrome; Klinefelter’s; KS; XXY: boys and men are born with ❖ Example: Pedigree Analysis of Hemophilia in the British Royal Family ❖ Importance: to trace up the illness and be able to undergo medical interventions so the future generations won’t inherit it  an extra X chromosome (error in the 23rd pair) – Down Syndrome; Trisomy 21: a person has an extra copy of chromosome 21 3. MOLECULAR GENETICS ❖ The study of the molecular structure of DNA, its cellular activities (including its replication), and its influence in determining the overall makeup of an organism ❖ Includes applications of Recombinant DNA (rDNA) technology (genetically modified organisms; GMO)