Structure and Function of Gene (part I) By Estri Laras Arumingtyas Fatchiyah Irfan Mustafa Gregor Mendel One of the pioneers in genetics One of the pioneers in genetics Used scientific approach to understand genetic features: Used scientific approach to understand genetic features: Character: is a heritable feature like flower colorCharacter: is a heritable feature like flower color Trait: Each variant for a characterTrait: Each variant for a character Gregor Mendel in 1857 started to experiment with: Gregor Mendel in 1857 started to experiment with: Pea PlantsPea Plants Traits: Character: CharacterDominant traitsRecessive traits 1857 Experiment To explain his results, Mendel formulated a hypothesis that included the following: 1. In the organism there is a pair of factors that controls the appearance of a given characteristic. (We call them genes.) 2. The organism inherits these factors from its parents, one from each. 5. If an organism has two unlike factors (we call them alleles) for a characteristic, one may be expressed to the total exclusion of the other (dominant vs recessive). 4. When the gametes are formed, the factors separate and are distributed as units to each gamete. This statement is often called Mendel's rule of segregation. 3. Each is transmitted from generation to generation as a discrete, unchanging unit. (The wrinkled seeds in the F2 generation were no less wrinkled than those in the P generation although they had passed through the round-seeded F1 generation.) Mendels principle of Segregation Pairs of alleles segregate (separate) during gamete formation; the fusion of gametes at fertilization creates allele pairs again Pairs of alleles segregate (separate) during gamete formation; the fusion of gametes at fertilization creates allele pairs again Ex: Tt organism Each gamete gets either T or t, but not bothEach gamete gets either T or t, but not both Mendel did not stop here He went on to cross pea varieties that differed in six other qualitative traits. In every case, the results supported his hypothesis. He went on to cross pea varieties that differed in six other qualitative traits. In every case, the results supported his hypothesis. He crossed peas that differed in two traits. He found that the inheritance of one trait was independent of that of the other and so framed his second rule: the rule of independent assortment. He crossed peas that differed in two traits. He found that the inheritance of one trait was independent of that of the other and so framed his second rule: the rule of independent assortment. Mendels principle of Independent Assortment By then doing an F1 cross (RrYy x RrYy) Mendel showed that the allele for yellow (Y) didnt always end up in the same gamete with the allele for round (R) By then doing an F1 cross (RrYy x RrYy) Mendel showed that the allele for yellow (Y) didnt always end up in the same gamete with the allele for round (R) Genes for different traits can segregate independently during the formation of gametes Genes for different traits can segregate independently during the formation of gametes Animal Inheritance Human Inheritance Mendels Model Alternative versions of genes account for variation in inherited characters Alternative versions of genes account for variation in inherited characters Alleles are alternative versionsAlleles are alternative versions Chromosome Gene LocusChromosome Gene Locus For each character, an individual inherits 2 alleles (P1 and P2): For each character, an individual inherits 2 alleles (P1 and P2): Two alleles being different have dominant or recessive alleles Two alleles being different have dominant or recessive alleles Dominant allele is expressed Dominant allele is expressed Structure and Function of Gene (part II) By Estri Laras Arumingtyas Fatchiyah Irfan Mustafa What is Inheritance? Passing on genetic information from parents to offspring Passing on genetic information from parents to offspring Humans have 23 pairs of chromosomes (46 total) Humans have 23 pairs of chromosomes (46 total) 1 of each pair is from one parent and the other is from the other parent1 of each pair is from one parent and the other is from the other parent Chromosomes Chromosomes, threadlike structures, first observed by Nageli in Chromosomes, threadlike structures, first observed by Nageli in Long strands of DNA that carry the genetic information on building and sustaining a living human being. Long strands of DNA that carry the genetic information on building and sustaining a living human being. Each chromosome contains many genes Each chromosome contains many genes What is a Gene? A segment of a chromosome that containing the code for a single protein (enzyme) A segment of a chromosome that containing the code for a single protein (enzyme) - The enzyme causes a chemical reaction that allows a trait to be expressed. ie. Production of a pigment Something that stated by Mendel as factor Something that stated by Mendel as factor Round vs Wrinkled Dominant allele round codes for enzyme that converts sugar starch Dominant allele round codes for enzyme that converts sugar starch Recessive allele have defective enzyme Recessive allele have defective enzyme Sugar accumulatesSugar accumulates Water diffuses in the seedWater diffuses in the seed Seeds swellSeeds swell Mature seed when dried becomes wrinkledMature seed when dried becomes wrinkled One dominant allele produces enough enzymeOne dominant allele produces enough enzyme Both homozygous dominants and heterozygotes produce enough enzymeBoth homozygous dominants and heterozygotes produce enough enzyme Alleles Alleles are alternate forms of a gene Alleles are alternate forms of a gene Homozygous individuals have two identical alleles for a traitHomozygous individuals have two identical alleles for a trait ex.: AA or aa organism Heterozygous individuals have two different alleles for a traitHeterozygous individuals have two different alleles for a trait ex.: Aa organism ex.: Aa organism Chromosomes are threadlike structures composed of DNA molecules Nucleus (center of cell) contains chromosomes and genes A gene, a segment of DNA (spiraled double chain) containing the hereditary code The body contains trillions of cells Cell, chromosome and gene (DNA) chromatin The Structure of Chromosome Nucleotides --> DNA --> Gene --> Chromosome Nucleotides --> DNA --> Gene --> Chromosome Human DNA is ~ 2 meters long. The nucleus of DNA is about 6 M in diameter. Human DNA is ~ 2 meters long. The nucleus of DNA is about 6 M in diameter. So, how the very long DNA is packed into a very small nucleus? fatchiyah, JB UB Chromosome Structure Type of chromosome structure Metacentric Chrom. 1 Acrocentric Chrom. 14 Submetacentric Chrom. 9 1.The short arm is designated as p and the long arm as q. 2.The centromere is the location of spindle attachment and is an integral part of the chromosome. 3.It is essential for the normal movement and segregation of chromosomes during cell division. The ideogram is basically a "chromosome map" showing the relationship between the short and long arms, centromere (cen). The specific banding patterns are also illustrated. Each band is numbered to aid in describing rearrangements. What molecule transmitting genetic inheritance from parents to offspring ? DNA DNA (Deoxyribose Nucleic Acid) THE STRUCTURE OF DNA nucleoside base sugar DNA: terminology nucleotides (nucleoside mono-, di-, and triphosphates) sugar phosphate(s) base sugar 1. DNA is double stranded 2. DNA strands are antiparallel 3. G-C pairs have 3 hydrogen bonds 4. A-T pairs have 2 hydrogen bonds 5. One strand is the complement of the other 6. Major and minor grooves present different surfaces 7.Almost all cellular DNA is B-DNA 8.B-DNA has ~10.5 bp/turn of the helix DNA: structure Gene expression in eucaryotes and procaryotes Molecular Definition of Gene The entire nucleic acid sequence that is necessary for the synthesis of a functional protein and RNA The entire nucleic acid sequence that is necessary for the synthesis of a functional protein and RNA Coding region (exon and intron) + Regulatory sequences (e.g. promoter= the site where RNA polymerase binds prior to the initiation of transcription ) Coding region (exon and intron) + Regulatory sequences (e.g. promoter= the site where RNA polymerase binds prior to the initiation of transcription ) Basic Gene Structures Eukaryotic genes Eukaryotic genes Exons,introns,Exons,introns, translation starts and stops, splice (donor/acceptor) junctionstranslation starts and stops, splice (donor/acceptor) junctions Basic Gene Structure Prokaryotic genes Prokaryotic genes coding regions, non-coding regionscoding regions, non-coding regions translation starts and stopstranslation starts and stops gene promoter startstop Prokaryotic genes are easier to identify than eukaryotic genes because of the simplicity of their gene structure and the density of genes in the genome