Agricultural Molecular Biology 555522

63
Agricultural Molecular Biology 555522

description

Agricultural Molecular Biology 555522. Agricultural Molecular Biology Teaching Team. ดร. อรรัตน์ มงคลพรเกษตร ดร. คนึงนิตย์ เหรียญวรากรเกษตร ดร. เสริมศิริ จันทร์เปรมเกษตร ผศ. ดร. สนธิชัย จันทร์เปรมเกษตร ดร. จุรีย์รัตน์ ชำนาญพันธ์ศวท. ดร. ธีระพล ศิรินฤมิตรสัตวแพทย์. - PowerPoint PPT Presentation

Transcript of Agricultural Molecular Biology 555522

Agricultural Molecular Biology

555522

Agricultural Molecular BiologyTeaching Team

• ดร . อรร�ตน์� มงคลพร เกษตร• ดร . คน์�งน์�ตย์� เหร�ย์ญวรากร เกษตร• ดร . เสร�มศิ�ร� จั�น์ทร�เปรม เกษตร• ผศิ . ดร . สน์ธิ�ชั�ย์ จั�น์ทร�เปรม เกษตร• ดร . จั!ร�ย์�ร�ตน์� ชั"าน์าญพ�น์ธิ� ศิวท.• ดร . ธิ�ระพล ศิ�ร�น์ฤม�ตร ส�ตวแพทย์�

Agricultural Molecular BiologyCourse Structure

• Credit 3-0 : 45-hour program• Class schedules : Monday 9.00-10.30

Wednesday 9.00-10.30

CAB Lecture room 3rd floor• Evaluation :

– Exam I, II, III 75%, TBA– Presentation 10%– Paper 10%– Class participation 5%

• Grading system : Score-dependent

Agricultural Molecular BiologyCourse Textbooks

• Genes VII, 2000. By Benjamin Lewin.– 5 Reserved books, KPS library

• Molecular Biology, International Edition. 1999. By Weaver RE.

• Genomes, 1999. By TA Brown

What is molecular biology?

• A study of gene structure and function at the molecular level

• Molecular biology grew out of the disciplines of genetics and biochemistry

A brief history

• Transmission of genetics– Mendel’s law of inheritance– Chromosome theory of inheritance– Genetic recombination and mapping– Physical evidence for recombination

• Molecular genetics– Discovery of DNA– Composition of genes– Relationship between genes and proteins– Activities of genes

Transmission of genetics 1856 Gregor Mendel: inheritance of 7 traits in garden pea

Mendel’s laws of inheritance >> principle of segregation

• Genes exist in different forms called alleles.• One allele can be dominant over the other.• Mendel’s work: yellow seed > green seed

parents yellow x green

F1

yellow selfed

F2

3 yellow : 1 green

Mendel’s laws of inheritance >> principle of independent assortment

• 7 genes operated independently• Combinations of 2 different genes 9:3:3:1

Chromosome theory of inheritance

• 1900 rediscovery Mendel’s findings• First chromosome theory:

– Thomas Hunt Morgan: fruit fly (Drosophila melanogaster)

- -red eyed x white eyed

- most red eyed F1

red-eyed males x red-eyed females

1/4 white-eyed males + no white-eyed females

• Eye color is sex-linked, X chromosome– male has 1 copy, female has 2 copies

• Genes are located on chromosome : locus• Diploid organisms have 2 copies of chromosomes

– homozygous and heterozygous– genotype– phenotype : wild-type vs mutant

Genetic recombination and mapping

• Genes on separate chromosome behave independently, same chromosome behave as if they are linked

• Genes on same chromosome not perfect linked• Eye color and miniature wing on X chromosome are 65.5

% linked, with new combination ‘recombinants’• Answer is recombination process, a crossing over betwee

n homologous chromosomes during meiosis• Sturtevant: mathematical relationship between the dista

nce of genes and the recombination frequency• Barbara McClintock : physical evidence for recombinatio

n in maize chromosomes

Molecular genetics

• DNA discovery : 1869 Friedrich Miescher - nuclein– deoxyribonucleic acid (DNA)– ribonucleic acid (RNA) and protein

• Composition of genes– DNA or RNA or protein– Avery proved it was DNA– Bacteria transformation

• virulent dead cells + avirulent living cells• Relationship : genes and protein

Molecular genetics

• Relationship : genes and protein– How do genes work?– Human disease alcaptonuria -- black pigment in urine– Defective enzyme– A gene responsible for enzyme (protein) production

• Activities of genes– How do genes work?– Genes replicate faithfully– Genes direct production of RNAs and proteins– Genes accumulate mutations and allow evolution

Replication

• 1953 Watson and Crick• DNA structure is double helix• 4 bases composition : A, G, T and C

– A - T, G- C• semiconservative replication

Production of polypeptides

• Gene product is either RNA or polypeptides– gene expression

• Transcription : a single copy of DNA strand (RNA)• Translation : protein production

– mRNA carries genetic code to ribosomes– genetic code = codon consisting of 3 bases

• 61 amino acids, 3 stop signals• Accumulate mutations

– one base change -- sickle cell disease– deletions or insertions– transposon

Gene cloning

• Isolate genes and place them in new organisms• Benefits :

– raw materials for studies in molecular biology– protein product ie human insulin– Bt cotton

Genome structure and organisation>>what is genome?

• Genome is the entire DNA content of a cell, including all of the genes and all the intergenic regions

• Most genome are made of DNA• 2 types of living organisms

– prokaryotes: cells lack extensive internal compartmetns

– eukaryotes: cells contain membrane-bound compartments ie. Nucleus, mitochondria, chloroplast

• animals, plants, fungi and protozoa are eukaryotes

Why are genome projects important

Why are genome projects important?

• Genome sequences are the key to the continued development --opens the way to a comprehensive description of the molecular activities of living cells and the ways in which these activities are controlled

• Gene catalog -- isolation and untilisation of important genes

• Additional benefits -- study role of noncoding DNA• Challenge of unknown

Genomes of eukaryotes

• Eukaryotic genome is split into 3 components– nuclear genome– mitochondrial genome– chloroplast genome

• made up of 2 components: nuclear and mitochondria

Human genome

Human genome

• nuclear genome: – 3000 Mb DNA – linear genome divided into 24 (22 autosomes + 2

sex chromosome, X and Y)– shortest 55 Mb and longest 250 Mb

• mitochondrial genome:– circular DNA 16,569 bp

Human genome

• immensity of human genome– analog with normal font size --60 nt = 10 cm– genome sequence stretch for 5,000 km

Nuclear genome

• Genome size ranges <10 Mb to >100,000 Mb

• size broadly coincides with organism complexity

• larger genome --high repeats

Nuclear genome

• Split into a set of linear DNA molecules -chromosomes• chromosome number not related to organism features

Where are genes in a genome?>>Human EST map --expressed sequence tags

Families of genes

• Multigene family --groups of genes of identical or similar sequence– rRNA genes : 5S, 28S, 5.8S and 18S– globin gene families

• alpha-globin family, on chr#16• beta-globin family, on chr#11

• Supergene family– globin supergene family --alpha and beta evolve

from a single ancestral globin gene

Pseudogenes

• Genes which for one reason or another have become nonfunctional– conventional

pseudogenes --inactivation by mutation ie. Create termination codon within coding region

– processed pseudogenes -- abnormality during gene expression

Organelle genomes

• Mitochondria and chloroplasts• Extra chromosomal genes --unusual inheritance patterns• Most mitochondrial and chloroplast genomes are circular

Genetic content of organelle genomes

• Mitochondria display greater variability– number of genes : 12-92– genes for mitochondrial rRNAs, protein components

for respiratory chain• Chloroplasts are less variable

– gene number ~ 200– coding for rRNAs, tRNAs and ribosomal proteins and

proteins involved in photosynthesis

Prokaryotic genome

• Physical structure: size < 5 Mb• Genome is contained in a single circular DNA molecule

in nucleoid• Circular E. coli chromosome circumference is 1.6 mm,

while cell is 1x2 um

Supercoiling

Prokaryotic genome

• Plasmid: small piece DNA, often circular, coexist with main chromosome in a bacteria cell

• plasmids carry genes not present in main chromosome

Prokaryotic genome

• Controversy: should plasmid be part of genome?– E. coli : main chromosme 4.6 Mb+ few kb of plasmid

DNA which are not essential– Borrelia burgdorferi: 910 kb main chromosome

carrying 853 genes + 17 linear and circular plasmids of 533 kb with 430 genes, some of which are essential

Prokaryotic genome

• Genetic organisation: bacterial genomes have compact genetic organisations with little space between genes

Genetic organisation• Operons: an operon is a group of genes located

adjacent to one another in the genome• All genes in an operon are expressed as a single unit

Operon controversy

• Most cases, genes in an operon are functionally related, coding for a set of proteins involved in a single biochemical activity

• Some species, genes in an operon rarely have any biochemical relationship

Repetitive DNA

• Repetitive DNA found in all organisms, in some including humans shows substantial composition

Repetitive DNA

• There are various types of repetitive DNA– tandemly repeated

DNA– interspersed genome-

wide repeats• Tandemly repeats:

– common features of eukaryotes

– also called satellite DNA

Satellite DNA

• Satellite bands in density gradient made up of long series of tandem repeats, hundreds kb

• A genome can contain different types of satellites• Alphoid DNA: one type of satellites in centromere• Minisatellites: form clusters up to 20 kb with repeat

units up to 25 bp – telomeric DNA --important function in DNA

replication

Satellite DNA

• Microsatellites: shorter, usually < 150 bp with repeat unit 4 bp or less– although short, there are many --useful as markers

for mapping– in human, CA repeats make up 0.5% og genome or

15 Mb; A repeats 0.3%– function is mysterious, but useful to geneticists as

they are variable• number of repeats different in different members

of a species due to slippage during DNA replication --insertion or deletion

• No 2 humans have exactly the same combination of microsatellite alleles

Interspersed genome-wide repeats

• Interspersed repeats arise from transposition• Most repeats have inherent transpositional activity