lect10f1 cell nucleus 2011

8/3/2019 Lect10F1 Cell Nucleus 2011

http://slidepdf.com/reader/full/lect10f1-cell-nucleus-2011 1/9

11/21/20

Lecture 10:Lecture 10:CELL NUCLEUSCELL NUCLEUS

Controls cell activitiesContains the

hereditary material ofthe cell

Gene ProteinCellular functionOrganismal function

LECTURE FLOWLECTURE FLOW

1.1. INTRODUCTIONINTRODUCTION

2.2. STRUCTURE AND FUNCTION OFSTRUCTURE AND FUNCTION OFNUCLEUSNUCLEUS Nuclear MembraneNuclear Membrane NucleolusNucleolus ChromosomesChromosomes

3.3. THE GENETIC MATERIALTHE GENETIC MATERIAL DNADNA GenesGenes ChromosomesChromosomes

4.4. GENETIC CASESGENETIC CASES

1. INTRODUCTION1. INTRODUCTION

1.1. TheThe CELLCELL is the smallest unit of livingis the smallest unit of livingmattermatter

2.2. Cells are the basic and fundamental unitCells are the basic and fundamental unitof structure, physiology, and organizationof structure, physiology, and organizationof all living organisms.of all living organisms.

3.3. LifeLife dependsdepends on theon the abilityability of of cellscells totostorestore,, retrieveretrieve, and, and translatetranslate thethegeneticgenetic instructionsinstructions ((the hereditarythe hereditaryinformationinformation)) required to make andrequired to make andmaintain a living organism.maintain a living organism.

4.4. TheThe hereditaryhereditary informationinformation is passed onis passed onfrom a cell to its daughterfrom a cell to its daughter cellscells at cellat celldivision, and from one generation of andivision, and from one generation of anorganism to the next through the organism'sorganism to the next through the organism'sreproductivereproductive cellscells..

5.5. TheseThese instructionsinstructions are stored within everyare stored within everyliving cell as itsliving cell as its genesgenes, the, the informationinformation--containing elementscontaining elements that determine thethat determine thecharacteristics of a species as a whole and of characteristics of a species as a whole and of the individuals within it.the individuals within it.

6.6. Genes can be divided into two differentGenes can be divided into two different

classes of genes,classes of genes, regulatory genesregulatory genes andandeffectoreffector genesgenes..



11/21/20

7.7. EffectorEffector genes encode proteins that carrygenes encode proteins that carryout some task in the cell that modify theout some task in the cell that modify thestructure or metabolism of the cellstructure or metabolism of the cellleading to a developmental change.leading to a developmental change.

ManyMany effectoreffector genes encode enzymes that aregenes encode enzymes that arerequired for a particular biochemical pathway.required for a particular biochemical pathway.

8.8. Regulatory genes encode proteins thatRegulatory genes encode proteins thatfunction to regulate the expression of function to regulate the expression of other genes (other genes (FosketFosket, 1994), 1994)

2. STRUCTURE AND FUNCTION OF NUCLEUS2. STRUCTURE AND FUNCTION OF NUCLEUS

1.1. The nucleus is a highly specialized organelle thatThe nucleus is a highly specialized organelle thatserves as theserves as the

information andinformation andadministrativeadministrativecenter of thecenter of thecell.cell.

Yellowtang.org

1.1. Nucleus is a sphericalNucleus is a spherical--shaped organelle present inshaped organelle present inevery eukaryotic cell which accounts to about 10every eukaryotic cell which accounts to about 10percent of the cell's volume, and is the mostpercent of the cell's volume, and is the mostprominent one in comparison to other cell organelles.prominent one in comparison to other cell organelles.

2.2. Nucleus is separated from the rest of the cell or theNucleus is separated from the rest of the cell or thecytoplasm by a nuclear membrane.cytoplasm by a nuclear membrane.

3.3. The nucleus functions to store the cell's hereditaryThe nucleus functions to store the cell's hereditarymaterial (DNA), to coordinate the cell's activitiesmaterial (DNA), to coordinate the cell's activitieswhich include intermediary metabolism, growth,which include intermediary metabolism, growth,protein synthesis, and reproduction (cell division)protein synthesis, and reproduction (cell division)

In general, a eukaryotic cell has only one nucleus.In general, a eukaryotic cell has only one nucleus.Some eukaryotic cells are enucleate cells (withoutSome eukaryotic cells are enucleate cells (withoutnucleus) such asnucleus) such as red blood cellsred blood cells (RBCs), and some(RBCs), and someothers are multinucleate (consists of two or moreothers are multinucleate (consists of two or more

nuclei) such as slime moldsnuclei) such as slime molds

NUCLEUS STRUCTURENUCLEUS STRUCTURE A cell nucleus consistsA cell nucleus consists

of of 1.1. nuclear membranenuclear membrane

(nuclear envelope)(nuclear envelope)

2.2. NucleolusNucleolus

3.3. Nuclear poresNuclear pores

4.4. ChromatinChromatin

5.5. ChromosomesChromosomes

6.6. NucleoplasmNucleoplasm

NucleoplasmNucleoplasm, also, alsoknown asknown as karyoplasmkaryoplasm,,

is the matrix presentis the matrix presentinside the nucleus.inside the nucleus.

http://micro.magnet.fsu.edu/cells/plants/nucleus.html



11/21/20

1.1. Nuclear MembraneNuclear Membrane The nuclear membrane is a doubleThe nuclear membrane is a double--layered structurelayered structure

that encloses the contents of the nucleusthat encloses the contents of the nucleus

The outer layer of the membrane is connected to theThe outer layer of the membrane is connected to theendoplasmic reticulumendoplasmic reticulum

A fluidA fluid--filled space (filled space (perinuclearperinuclear space) is presentspace) is presentbetween the two layers of a nuclear membranebetween the two layers of a nuclear membrane

The nucleus communicates with the remaining of the cellThe nucleus communicates with the remaining of the cell(cytoplasm) through several openings called(cytoplasm) through several openings called nuclearnuclear

porespores..

Such nuclear pores are the sites for exchange of largeSuch nuclear pores are the sites for exchange of largemolecules (proteins and RNA) between the nucleus andmolecules (proteins and RNA) between the nucleus andcytoplasm.cytoplasm.

2.2. NucleolusNucleolus

The nucleolus (plural nucleoli) is a dense, sphericalThe nucleolus (plural nucleoli) is a dense, spherical--shaped structure present inside the nucleusshaped structure present inside the nucleus

Some of the eukaryotic organisms have nucleus thatSome of the eukaryotic organisms have nucleus thatcontains up to four nucleolicontains up to four nucleoli

The nucleolus plays an indirect role in protein synthesisThe nucleolus plays an indirect role in protein synthesisbyby producingproducing ribosomesribosomes..

TheseThese ribosomesribosomes are cell organelles made up of RNA andare cell organelles made up of RNA and

proteins; they are transported to the cytoplasm, whichproteins; they are transported to the cytoplasm, whichare then attached to the endoplasmic reticulum.are then attached to the endoplasmic reticulum.

RibosomesRibosomes are the proteinare the protein--producing organelles of aproducing organelles of acell. Nucleolus disappears when a cell undergoes divisioncell. Nucleolus disappears when a cell undergoes divisionand is reformed after the completion of celland is reformed after the completion of cell--division.division.

2.2. ChromosomesChromosomes

Chromosomes are present in the form of strings of Chromosomes are present in the form of strings of DNADNAandand histoneshistones (protein molecules) called(protein molecules) called chromatinchromatin..

The chromatin is further classified intoThe chromatin is further classified into heterochromatinheterochromatinandand euchromatineuchromatin based on the functions.based on the functions.

HeterochromatinHeterochromatin is a highly condensed,is a highly condensed, transcriptionallytranscriptionallyinactive form, mostly present in adjacent to the nuclearinactive form, mostly present in adjacent to the nuclear

membrane.membrane.

EuchromatinEuchromatin is a delicate, less condensed organizationis a delicate, less condensed organizationof chromatin, which is found abundantly in a transcribingof chromatin, which is found abundantly in a transcribingcell.cell.

NUCLEUS FUNCTIONSNUCLEUS FUNCTIONS

Nucleus controls the hereditary characteristics of anNucleus controls the hereditary characteristics of anorganism and is also responsible for the proteinorganism and is also responsible for the proteinsynthesis, cell division, growth, and differentiation.synthesis, cell division, growth, and differentiation.1.1. Storage of hereditary material, theStorage of hereditary material, the genesgenes in the form of in the form of

long and thin DNA (deoxyribonucleic acid) strands,long and thin DNA (deoxyribonucleic acid) strands,referred to asreferred to as chromatinschromatins..

2.2. Storage of proteins and RNA (ribonucleic acid) in theStorage of proteins and RNA (ribonucleic acid) in thenucleolus.nucleolus.

3.3. Nucleus is a site forNucleus is a site for transcriptiontranscription in which messenger RNAin which messenger RNA(mRNA) are produced for the protein synthesis.(mRNA) are produced for the protein synthesis.

4.4. Exchange of hereditary molecules (DNA and RNA) betweenExchange of hereditary molecules (DNA and RNA) between

the nucleus and rest of the cell.the nucleus and rest of the cell.5.5. During the cell division, chromatins are arranged intoDuring the cell division, chromatins are arranged into

chromosomes in the nucleus.chromosomes in the nucleus.



11/21/20

6.6. Production of Production of ribosomesribosomes (protein factories) in the(protein factories) in thenucleolus.nucleolus.

7.7. Selective transportation of regulatory factors and energySelective transportation of regulatory factors and energymolecules through nuclear pores.molecules through nuclear pores.

8.8. As the nucleus regulates the integrity of genes and geneAs the nucleus regulates the integrity of genes and geneexpression, it is also referred to asexpression, it is also referred to as the control center of athe control center of acellcell

3. THE GENETIC MATERIAL3. THE GENETIC MATERIAL

The nucleus is the cell organelle thatThe nucleus is the cell organelle thathouses the genetic material (DNA) inhouses the genetic material (DNA) ineukaryotic organism such as plantseukaryotic organism such as plants

The nucleus is the control center of aThe nucleus is the control center of aeukaryotic cell, responsible for theeukaryotic cell, responsible for thecoordination of genescoordination of genes andand gene expressiongene expressionthat regulate allthat regulate all cellcell activityactivity..

DNA (deoxyribonucleic acid) is the geneticDNA (deoxyribonucleic acid) is the geneticmaterial stored in the cell nucleusmaterial stored in the cell nucleus

What is the genetic material in the cell nucleus?

DNA is an alphaDNA is an alphadouble helix of twodouble helix of twopolynucleotidepolynucleotidestrands.strands.

http://ghr.nlm.nih.gov/handbook/basics/dna



11/21/20

DNADNA

-- DirectsDirects RNARNAsynthesissynthesis

-- DirectsDirects proteinproteinsynthesis throughsynthesis throughRNARNA

DNA is made up of DNA is made up of four basesfour bases (abbreviated(abbreviated A, T,A, T,C,C, andand GG) that are repeated over and over in) that are repeated over and over inpairs.pairs.

The sugar groupThe sugar group forms the backbone of DNA.forms the backbone of DNA.

The phosphate groupsThe phosphate groups are responsible for linkingare responsible for linkingone nucleotide to another.one nucleotide to another.

The nitrogenousThe nitrogenousbasesbases of nucleotidesof nucleotidesface each other andface each other andform Hydrogenform Hydrogenbonds with theirbonds with theircomplimentarycomplimentarybases.bases.

Double strandedDouble strandedDNA formed byDNA formed bycomplementarycomplementaryBase PairingBase Pairing

G≡CG≡C

A=TA=T

A G≡C bondA G≡C bond

is thermallyis thermallymore stablemore stable

than an A=Tthan an A=Tbond.bond.

EachEachpolynucleotidepolynucleotideconsists ofconsists ofmonomers calledmonomers callednucleotidesnucleotidesconnected to eachconnected to eachother by aother by aphosphodiesterphosphodiesterlinkageslinkages

Nucleic acids exist as polymers calledNucleic acids exist as polymers called polynucleotidespolynucleotides



11/21/20

Genes are the tiny, basic unitsof inheritance found in DNA(short regions of the DNA) thathold the information needed tobuild and maintain the body.-- Genes have fixed locations: eachGenes have fixed locations: each

gene is in a particular place on agene is in a particular place on aparticular chromosomeparticular chromosome

- Genes determine color, size, and make-up for every livingspecies.

- Each equine species receives half of their genes from theirsire (father) and half from their dam (mother).

- Physically, genes are linked together like a strand of pearls toform a chromosome.

What are Genes? The genetic code is the sequence of bases onThe genetic code is the sequence of bases on oneoneof the strandsof the strands..

A geneA gene isis a specifica specificsequence of basessequence of baseswhich has thewhich has theinformation for ainformation for aparticular protein.particular protein.

Genes, a long strand of DNA (RNA in someGenes, a long strand of DNA (RNA in someviruses), contains aviruses), contains a promoterpromoter whichwhichcontrols the activity of a gene, and acontrols the activity of a gene, and acoding sequencecoding sequence which determines whatwhich determines whatthe gene produces.the gene produces.

In most eukaryotic genes,In most eukaryotic genes, coding regionscoding regions((exonsexons) are interrupted by) are interrupted by noncodingnoncodingregionsregions ((intronsintrons))

During transcription, the entire gene isDuring transcription, the entire gene iscopied into a precopied into a pre--mRNA, which includesmRNA, which includes

exonsexons andand intronsintrons..

• During the process of RNA splicing, intronsare removed and exons joined to form acontiguous coding sequence. This "mature"mRNA is ready for translation



11/21/20

Organism 2n Notes

Adders-tongue (Ophioglossum reticulatum )

1200 or1260

This fern has the highest knownchromosome number.

Human (Homo sapiens ) 46 44 autosomaland 2 sex

Maize (Zea mays ) 20

Mango (Mangiferaindica ) 40

Mosquito (Aedesaegypti ) 6

The 2n=6 chromosome number isconserved in the entire familyCulicidae, except in Chagasiabathana which has 2n=8.

Rice (Oryza sativa ) 24

Soybean (GlyneMax L.) 40

Jack jumper ant (Myrmecia pilosula )

2

2 for females, males are haploidand thus have 1; smallest numberpossible. Other ant species have

more chromosomes.[18]

Number of ChromosomesNumber of ChromosomesHUMAN CHROMOSOMESHUMAN CHROMOSOMES

We have 46chromosomes, or 23pairs.

44 of them are calledautosomes (No. 1-22).

No.No. 2323 areare sexsexchromosomeschromosomes

Chromosome 1 is thelongest, 22 is theshortest.

• The sex chromosomes: the X chromosome and the Ychromosome.

• Males have and X and a Y;→XY

• Females have 2 X’s ;→ XX.

GENETIC CASESGENETIC CASES



11/21/20

Sex DeterminationSex Determination

• An egg contributes an X

chromosome

• A sperm contributeseither an X or a Y

chromosome

• A gene on the Ychromosome (SRY)determines sex

Sex Determination Sex Determination

About 4 weeks after fertilizationAbout 4 weeks after fertilization

– – an embryo that contains thean embryo that contains the SR YSR Y genegenedevelops testes,develops testes, the primary male sexthe primary male sexorganorgan

– – The testes secrete the hormoneThe testes secrete the hormonetestosteronetestosterone that signals the other cellsthat signals the other cellsof the embryo to develop in the maleof the embryo to develop in the malepattern.pattern.

– – If the embryo does not have theIf the embryo does not have the SR YSR Y gene,gene,it develops ovaries instead, which secreteit develops ovaries instead, which secreteestrogenestrogen and causes development in theand causes development in thefemale pattern.female pattern.

lect10f1 cell nucleus 2011

Documents