Genetics Lec.1 PDF

Genetics for 2ry level students  Genetics 1. Part one: Identification and organization of genetic material…Dr. Hanan Ramadan 2. Part two: Function of genetic material Prof Dr. Magda Noshy 1. Part three: Phenotyping and variation in the genetic material…Dr....

Genetics for 2ry level students  Genetics 1. Part one: Identification and organization of genetic material…Dr. Hanan Ramadan 2. Part two: Function of genetic material Prof Dr. Magda Noshy 1. Part three: Phenotyping and variation in the genetic material…Dr. Heba Bassiona  Part one Identification Organization 1-Requirements 1-Structure and organization of 2-DNA &RNAstructure prokaryotic cromosomes 3-Relating DNA structure 2-structure and organaziation to genetic requirements of eukaryotic chromosomes A- chromosomes morphology 4-Evidences in both pro- and eukaryotes B-chromosomes identification C-molecular structure of chromosomes  Lecture one 1-Requirements of genetic material 2-Nucleic acid structure 3-Relating DNA structure to genetic requirements  Introduction Genetics is a science devoted to study the underlying bases of heredity and variation Heredity “like begets like” its major focus on studying how information is stored on gene (basic heredity unit) Genetic research are focused on transmission, molecular and population genetics  \] Genetics research Molecular genetics Transmission (Mendelian ) Population genetics Studying biochemical 1-Inferring gene function and molecular 1-Factors that determine mechanisms by which the genetic composition 2-Rules establishment of populations hereditary information 3-Mapping of gene is stored into DNA and 2-How genetic changes location induced new isolated subsequently transmitted to protein groups called species PCR Sequencing Molecular geneticsm  Identification of genetic material 1- Requirements to be genetic material are: contain biologically useful information in a stable form able to reproduce and transmitte faithfully able to express itself must be capable of variation. Genetic mutation occur by two sources mutations and recombination  DNA II- structure of nucleic acid It consists of nucleotides RNA Each nucleotides consists of phosphate group + sugar + nitrogen base  Differences between DNA&RNA RNA is single strand while DNA is double strand Ribose in RNA and deoxyribose in DNA RNA contains uracil in place of thymine in DNA RNA molecules are much shorter than DNA molecules  RNA classes Functional RNAs Functional or Informational Functional RNA not ? RNAs (rRNA & tRNA Specific for eukaryotic cells microRNA (mRNA) in all organisms) and small tRNA rRNA Small nuclear and cytoplasmic RNA interfering RNA  RNA classes 1. Informational RNAs (mRNA) Messenger RNA (mRNA) is the informational RNA from which proteins are directly synthesized Intermediates in the process of decoding genes into polypeptide chains Carries the genetic information from DNA to be translated by ribosomes 2. Functional RNAs in all organisms They are never translated into polypeptide chains The two classes transfer (tRNA) and ribosomal (rRNA) RNAs are found in all organisms tRNAs transfer amino acids to the mRNA during protein synthesis rRNAs combine with different protein arrays to form ribosomes “the machines” used for protein synthesis 2. Functional RNAs specific for eukaryotes Small nuclear (snRNAs) take part in the splicing of primary transcripts (pre-mRNAs) into mRNAs in the nucleus Spliceosomes are small ribonucleoprotein particles resulting from combination of snRNAs with specific proteins Small cytoplasmic (scRNAs) direct protein traffic within the eukaryotic cell microRNAs and small interfering RNAs They are small non-coding RNA molecules central for RNA interference Via RNA silencing and post-transcriptional regulation of gene expression miRNAs pair with complementary sequences within mRNA molecules resulting in mRNA silencing by one or more of the following: 1- mRNA cleavage into two pieces 2- Shortening poly A tail resulting in destabilization of mRNA 3- Decreasing the efficient mRNA translation into proteins  Difference between miRNAs and siRNAs The RNA interference pathway of siRNAs resemble that of miRNAs But miRNAs differ from siRNAs in that: miRNAs derive from RNA regions that fold back on themselves to form short hairpins whereas siRNAs derive from longer regions of double-stranded RNA  III-Relating DNA structure to its genetic requirements 1. DNA as a coded molecule The information content of DNA resides in the sequence of its bases Different species having different genetic information Chargaff’s experiment: indicated that equal amount of purine and pyrimidines obtained by chemical hydrolysis of DNA A+G= T+C →A+G/T+C=1 This percentage remains constant for the same species  2-DNA replication DNA replication is semi conservative, each one acts as template for new strand synthesis A- prokaryotes experiment 1-Bacteria were grown in a medium containig heavy isotope of nitrogen 2-Bacteria were then allowed to grow a mediumcontainig a light isotope nitrogen Control group F1 generation DNA F2 generation DNA (one unlabeled Labeled parent DNA (unlabeled DNA) (one heavy/light hybrid molecule, one heavy/light hybrid (one heavy /light molecule) molecule) hybrid molecule) B-Eukaryotes experiment  3-DNA translation It’s the third requirement of genetic material DNA nucleotide sequences translated into amino acid sequence during protein synthesis Gene is a group of nucleotides that control the synthesis of single polypeptide chain Genes ddid not share directly into protein synthesis, explain.  4-DNA variation It occurs by mutation and recombination processes Mutation is any change in the base sequence of DNA caused change in the contained genetic information and newly synthesized protein Recombination explained by several mechanisms that involved any genetic exchange between any two homologous chromosomes during meiosis  Synapsis and crossing over Synapsis, the process of fusion that occurs between homologs chromosomes pairs verly early in prophase 1. Prophase I is itself divided into the five substages: leptotene, zygotene, pachytene, diplotene and diakinesis Crossing-over: is an exchange of DNA between non-sister chromatids contacted togther throughout pachytene as a result of localized breakage of the DNA thus produces "cross-over chromatids," each composed of distinct blocks of DNA, some blocks derived from the mother, others from the father. Chisamata is a region shaped like an X where the two homologous chromosomes are physically joined and at least one found. Synaptonemal is a protein-RNA complex helps align corresponding regions of homol. chromo. allowing recombination