Basic Genetics Lecture PDF

BASIC GENETICS DR. LÁSZLÓ KASZÁS  GENE USEFUL TERMS STRUCTURALLY AND FUNCTIONALLY DISTINCT SECTIONS (BASE SEQUENCES) IN THE DNA CHAIN THAT ARE RESPONSIBLE FOR SPECIFIC TRAITS AND ENCODE RNA AND PROTEINS ALLELE A VARIATION...

BASIC GENETICS DR. LÁSZLÓ KASZÁS  GENE USEFUL TERMS STRUCTURALLY AND FUNCTIONALLY DISTINCT SECTIONS (BASE SEQUENCES) IN THE DNA CHAIN THAT ARE RESPONSIBLE FOR SPECIFIC TRAITS AND ENCODE RNA AND PROTEINS ALLELE A VARIATION OF A GENE LOCATED ON A PARTICULAR SECTION OF THE CHROMOSOME HOMOZYGOTE TWO ALLELES OF A GENE ARE IDENTICAL, AA OR aa HETEROZYGOTE TWO ALLELES OF A GENE ARE DIFFERENT Aa DOMINANT ALLELE EXPRESSED EVEN IF ONE ALLELE IS PRESENT RECESSIVE ALLELE CAN ONLY EXPRESS IN PAIRS GENOTYPE THE GENETIC STRUCTURE THAT GIVES RISE TO A TRAIT, THE MATERIAL BASIS FOR THE INHERITANCE OF A TRAIT PHENOTYPE THE SET OF OBSERVABLE TRAITS THAT MAKE UP THE TRAIT, THE FORM IN WHICH IT IS EXPRESSED WHERE CAN BE DNA FOUND IN PLANT CELLS? Every cell in plant contains the same genetic information Cellular organelles containing hereditary material: nucleus chloroplast mitochondria Gene transfer between organelles is typical ORGANISATION OF CELLULAR DNA DNA is a nucleic acid that The two strands of DNA are stores genetic information. antiparallel - one strand determines the other. Discovered by Friedrich Meischer in 1869. The opposite bases are connected by H-bonds. 3 main components: Basis (adenine, cytosine, guanine, thymine) Pentose (2-dezoxi-β-d-riboz) Phosphorus acid  ORGANISATION OF CELLEULAR DNA HISTONE PROTEINS – BASIC PROTEINS INVOLVED IN DNA UNWINDING 5 TYPES: H2A, H2B, H3, H4 – HISTONE CORE – NUCLEOSOME H1 – NUCLEOSOME BINDING PROTEIN 60 bp DNA SECTION BETWEEN TWO NUCLEOSOME WHY FOLDING IS IMPORTANT: NOT TO GET TANGLED IN THE DNA STRAND DO NOT BREAK DO NOT CLUMP The DNA length of a human cell is ~2m. ORGANISATION OF CELLULAR DNA – CHROMOSOME CENTROMERE REGIONS PLAY A ROLE IN CHROMOSOME PAIRING AND CHROMOSOME DISPLACEMENT DURING CELL DIVISION. BINDING SITE OF MICROTUBULES. COHENSIN: PROTEINS THAT LINK HOMOLOGOUS CHROMOSOMES TELOMERE REGION TANDEM REPEATS AT THE ENDS OF CHROMOSOMES IT HAS AN IMPORTANT ROLE IN STABILISING CHROMOSOME ENDS, COMPLETING REPLICATION PREVENTING THE LOSS OF SEQUENCE ENDS ORGANISATION OF CELLULAR DNA – STRUCTURE OF A GENE PROMOTER REGION: pre-transcriptional regulatory stage Rna-polymerase recognition space Influence velociti or duration of the trascription CODING REGION: the part of the gene that is transcribed into mRNA and then into protein during transcription EXON: which encode the protein subunits produced by the gene INTRON: which does not encode any part of the protein produced by the gene TERMINATION SEQUENCE: non-translating regulatory region in direction 3' of the translational, the stop marker ORGANELLAR DNA ORGANIZATION - PLASTID GENOME (ptDNA) NUMBER OF CHLOROPLASTS IN PLANT CELL 10-100, ~5-10 µm PLASTID GENOME - cpDNA THE PLASTID GENOME CONTAINS APPROXIMATELY 120–130 GENES TOTAL, INCLUDING AROUND 80 PROTEIN-CODING GENES, AND A VARIETY OF rRNA AND tRNA GENES SINGLE-SIZED CIRCULAR FORM OF DNA, BUT CAN BE LINEAR OR BRANCHED THE GENOME SIZE IS ABOUT 0.1 - 0.001% OF THE CELL'S NUCLEAR GENOME BUT CAN BE AS MUCH AS 5-10% OF THE TOTAL DNA CONTENT OF THE CELL. DIFFERENT TYPES OF PLASTIDS HAVE THE SAME GENETIC COMPOSITION PLASTID GENOME – cpDNA CIRCULAR DNA TYPICALLY CONTAINS AN INVERTED REPETITIVE REGION OF IRA AND IRB, WHOSE GENES ARE CONTAINED IN TWO COPIES OF THE PLASTID DUE TO REPETITION. THE IRA AND IRB SECTIONS ARE SEPARATED BY SEGMENTS CONTAINING THE GENES THAT OCCUR IN A COPY. THESE SECTIONS ARE NOT OF EQUAL LENGTH - SSC AND LSC REGIONS NON-CODING REGIONS ARE RARE GENES ARE FOUND IN HIGH DENSITY ON BOTH STRANDS (100-200) CODED GENES CAN BE DIVIDED INTO TWO GROUPS: rRNA FOR TRANSLATION, TRANSCRIPTION, tRNA, RIBOSOMAL PROTEIN, RNA POLYMERASE SOME OF THE GENES RESPONSIBLE FOR PHOTOSYNTHESIS, PHOTOSYNTHETIC APPARATUS AND CO2 FIXATION ORGANISATION OF MITOCHONDRIAL GENOME CELLULAR ORGANELLES FOR ENERGY PRODUCTION AND STORAGE (ATP SYNTHESIS) BACTERIAL SHAPE (SPHERE OR CYLINDER) DOUBLE MEMBRANE SYSTEM  MITOCHONDRIAL GENOME (mtDNS) GREATER DIVERSITY THAN THE PLASTID GENOME 100-3000 kbp in length. 2400 kbp CIRCULAR, DOUBLE-STRANDED DNA, BUT THE SIZE OF 850 kbp THE RINGS IS VARIABLE! 330 kbp CODED GENES CAN BE DIVIDED INTO TWO GROUPS: „HOUSEKEEPING” – GENES OF rRNA-EK, tRNA AND PROTEINS SOME GENES REQUIRED FOR MITOCHONDRIAL FUNCTION, ATP SYNTHASE, NADPH-DEHYDROGENASE, ETC. CELL CYCLE (IN PALNTS ~29 HOUR) PROCESS THAT OCCURS IN EUKARYOTIC CELLS BETWEEN TWO DIVISIONS IT CONSISTS OF INTERPHASE, MITOSIS AND CELL DIVISION STAGES: G1 – FIRST GROWING STAGE G0 – CELLS ARE PLACED IN AN UNCHANGED STATE, WAITING FOR A SIGNAL TO ENTER THE CELL CYCLE S – DNA DUPLICATION G2 – SECOND GROWING STAGE, PRIPERING THE DIVISON M – MITOSIS AND CYTOKINESIS, THE CELL SPLITS INTO TWO DAUGHTER CELLS REGULATOR: CYCLIN AND CYCLIN-DEPENDENT KINASE (CDK) PROTEINS  CELL CYCLE – S PHASE = DNA REPLICATION DNA replication is a semiconservative process - both strands are templet! REPLICATION CONSISTS OF 3 PHASES: INITIATION FORMATION OF A REPLICATION ORIGIN (HELIKSE) REPLICATION FORK ELONGATION DNA SYNTHESIS CAN ONLY OCCUR IN THE 5'-3' DIRECTION TERMINATION TELOMERE SECTIONS  CELL CYCLE – M PHASE=DIVISION MITOSIS: CHARACTERISTIC OF FERTILISED EGGS AND SOMATIC CELLS. IT CONSISTS OF THE DUPLICATION OF CHROMATIN IN THE NUCLEI, WHICH ARE SEPARATED TO FORM TWO DAUGHTER CELL NUCLEI WITH THE SAME NUMBER OF CHROMOSOMES AS BEFORE THE DIVISION. PROPHASE: THE CHROMATIN POPULATION CONDENSES INTO HIGHLY ORGANISED CHROMOSOMES. PAIRING OF HOMOLOGOUS CHROMOSOMES FORMATION OF NUCLEOSOMES, FORMATION OF CENTROSOMES METAPHASE: CELL MEMBRANE DISOLVES MICROTUBULES HAVE LOCATED AND ATTACHED TO THE KINETOCHORES CHROMOSOMES ARE IN THE EQUATORIAL LINE ANAPHASE: THE SISTER CHROMATIDS SEPARATE, THE TRAILING FILAMENTS SHORTEN TOWARDS THE CORRESPONDING CENTROSOME TELOPHASE: DESPIRALISATION OF CHROMOSOMES, RE-FORMATION OF THE NUCLEUS, RE-ASSEMBLY OF THE NUCLEAR ENVELOPE, AND FINISH THE CYTOKINESIS  CELL DIVISION - CYTOKINESIS PHYSICAL DIVISION OF THE CELL. THE CYTOPLASM BEGINS TO BE CONSTRICTED IN THE ANAPHASE BUT IS ONLY EVIDENT IN THE TELOPHASE. IN THE MIDDLE, THE CELL GRADUALLY BECOMES CONVOLUTED ALONG THE MITOTIC SPINDLE AXIS, FORMING A CONTRACTILE RING SYSTEM IN THE EQUATORIAL PLANE, WHICH BEGINS TO FORM A TIGHT JUNCTION BETWEEN THE TWO PROGENY CELLS. AFTER A SHORT PERIOD OF TIME, THIS CONTACT IS BROKEN AND THE CYTOPLASM OF THE TWO PROGENY CELLS SEPARATES COMPLETELY, AFTER WHICH THE MICROTUBULES CHARACTERISTIC OF THE INTERPHASE CELL ARE RE- ESTABLISHED IN BOTH CELLS AND THE ORGANELLES ARE DIVIDED. CELL DIVISION – MEIOSIS 2 MAIN STAGES: 1. STAGE: PAIRING OF HOMOLOGOUS CHROMOSOMES CROSSING OVER HOMOLOGOUS CHROMOSOMES ARE PULLED TOWARDS THE TWO POLES OF THE CELL, BUT THE THEY ARE NOT YET SEGREGATING PARTIAL START OF CYTOKINESIS 2. STAGE: ESSENTIALLY A MITOTIC DIVISION  MEISIS – CROSSING OVER DURING THE PRESEQUENCE OF THE MAIN STAGE I, THE INDIVIDUAL STAGES OF THE TWO MEMBERS OF THE HOMOLOGOUS CHROMOSOME PAIRS CAN BE EXCHANGED. THIS PROCESS IS CALLED ALLELE SUBSTITUTION, WHICH RESULTS IN THE TRANSFER OF GENE SEQUENCES LOCATED ON THE SAME SEGMENT OF HOMOLOGOUS CHROMOSOMES BETWEEN THE TWO CHROMOSOMES. DURING ALLELIC SUBSTITUTION, THE ARMS OF HOMOLOGOUS CHROMOSOMES CROSSING OVER AND THE CORRESPONDING SEGMENTS OF HOMOLOGOUS CHROMOSOMES ARE EXCHANGED. THE RESULT IS GENETIC VARIATION. THE RANDOM SEGREGATION OF CHROMOSOMES OF PATERNAL AND MATERNAL ORIGIN, ALLELIC REPLACEMENT, AND THE RANDOM PARTICIPATION OF INDIVIDUAL GAMETES IN FERTILISATION ARE COLLECTIVELY KNOWN AS RECOMBINATION. THANK YOU!