Rawy Shaaban

BIOL*1090 Final

The Nucleus1

Functions of the nucleus:

Storage, replication, and repair of genetic material

Expression of genetic material (transcription and splicing).

Ribosome biosynthesis

Structure of the nucleus

Nuclear envelope

Nuclear membrane

Nuclear pores

Nuclear lamina

Contents: chromatin, nucleoplasm, matrix, nucleolus

The Nuclear Envelope:

Consists of 2 parallel phospholipid bi-layers

The outer membrane binds ribosomes and is continuous with the rough ER.

The inner membrane bears integral proteins, which connect to the nuclear lamina.

The nuclear envelope separates transcription & translation. It acts as a selective barrier that limits movement of molecules. Its supported by the nuclear lamina, which is a thin meshwork of filamentous proteins bound to the inner membrane of the nuclear envelope by integral proteins. Its the attachment site for chromatin and support structure for NE.

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Nuclear pores:

Gateways between cytoplasm and nucleoplasm

3000 to 4000 pores per nucleus

Formed when inner and outer membrane fuse.

Contain a complex protein structure - the Nuclear Pore Complex.

The Nuclear Pore Complex:

Composed of nucleoporins

Has octagonal symmetry

Fits into the pore

Projects into cytoplasm and nucleoplasm

Functions of NPC:

Passive diusion of mole-cules smaller than 50 kDa (fast)

Regulated movement of larger molecules (slow)

Regulated movement of proteins into the nucleus requires a nuclear localization signal, a short stretch of positively charged amino acids within the protein.

Cellular function is acutely dependent upon nuclear import and export - Nucleocytoplasmic tracking of nucleotides, structural proteins, and DNA pack-aging proteins.

Factors needed for nuclear import are; a nuclear localization signal (NLS) in the cargo protein, karyo-pherins, energy, and Ran-Small G proteins that act as chemical messengers and triggers (when at-tached to 3 phosphate groups, they are turned on

and when attached to 2 phosphate groups they are turned o).

Nuclear exports are mostly protein and RNA mole-cules containing NES, exportins bound to the NES, and Ran-GTP - hydrolysis of which releases the cargo.

The nucleolus comprises of clusters of ribosomal DNA (rDNA) gathered together as one to several nu-cleoli that produce ribosomes.

Functions of the Nucleolus:

Ribosome biogensis

Synthesis of rRNA

Processing of rRNA

Assembly of subunits (rRNA + proteins)

Small 40S (18 RNA + 33 proteins) and large 60S subunits exported to the cytoplasm

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The Cytoskeleton2

The cytoskeleton is a dynamic network of pro-tein filaments that forms the cellular scaold-ing as well as transport system for organelles and vesicles. Its primary functions are:

Structural support

Intracellular support

contractility and motility

Spatial organization within the cell

There are three major elements: Microtu-bules, micro-filaments, and intermediate filaments.

Microtubules

Largest cytoskeletal element comprising of polymers of a-tubulin and B-tubulin proteins. Hetero-dimers are aligned in the same direc-tion which results in structural polarity - which is important for growth/shrinkage and direction of movement of material. MTs have a fast-growing + end and slow-growing - end.

The motor proteins use ATP to generate force and movement.

Dynein (- end directed).

Kinesin (+ end directed).

Microtubules undergo dynamic assembly and disassembly - this leads to rapid turnover of most MTs within the cell - dynamic instabil-ity. Shrinkage can occur very rapidly at the plus end, this is termed catastrophe.

Formation of MTs is regulated and controlled by MAPs (microtubule-associated proteins). Microtubule-organizing centers (MTOC) are the central sites of MT assembly.

Intermediate Filaments

Exclusive to multicellular animals, they pro-vide structural support and mechanical strength. Relative to MTs, they are stable fi-brous proteins of which there are 5 classes.

a-helical domains wrap around each other forming a rope-like dimer. Monomers are aligned in parallel and dimers are polar mole-cules with dierent N and C termini. Dimers associate anti-parallel; Once assembled, the filaments are not polar.

Microfilaments

Smallest cytoskeleton element comprising of polyers of the protein actin. Several well-characterized functions are maintenance of cell shape, cell movement, cytokinesis, and muscle contraction.

G-actin monomers have a polar structure as the monomors are incorporated in the same orientation. F-actin filaments are polar with a + end and - end.

F-actin assembly is a result of G-actin po-lymerizing reversibly due to nucleation (slow) or elongation (fast).

Polymerization and structure organization of F-actin filaments are regulated by actin-bonding proteins.

Myosin is an F-actin associated motor pro-tein. It must move towards the + end and is divided into conventional and unconven-tional myosins. Unconventional myosins generate force and contribute to motility in non-muscle cells.

All motor proteins are involved in vesicular transport.

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The Extracellular Space extends outwards from the surface of the plasma membrane and contains a variety of secreted materials (from the cell) that influence cellular behaviour.

It mediates cell-cell and cell-extracellular matrix (ECM) interactions

Provides mechanical protection

Serves as a barrier

Binds regulatory factors

Cells of bacteria, plants, and fungi are surrounded by a cell wall, which is considered an ECM.

Plant cell walls:

Composed of cellulose, hemicellulose, pectin, and proteins

Provides structural support to the cell and to the organism as a whole (skeleton)

Protects the cell from mechanical damage and pathogens

Contain biochemical information for the cell

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~ End of Pre-midterm material ~

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DNA3

DNA is a polymer. Each subunit is a nucleotide comprised of:

a phosphate group

a five carbon sugar

one of four cyclic nitrogenous bases

The purine and pyrimidine nucleotides in polynucleotide chains are connected by phosphodiester bonds.

DNA is double-stranded and the strands are antiparallel.

The strands are held together by hydrogen bonds between bases on opposing strands and by hydropho-bic interactions between adjacent stacked bases.

Each DNA strand has chemical polarity. The 5 end has a free phosphate group and the 3 end has a free hydroxyl group.

Opposing strands are said to be complementary.

Base pairing is specific and is mediated by hydrogen bonds

The most common form of DNA is called B-DNA

There are two grooves of dierent width: the major groove and minor groove

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The four nucleotides of DNA are:

Rawy Shaabanpurines

Rawy Shaabanpyrimidines

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Rawy ShaabanThe structural difference between purines and pyrimidines is that purines are made up of two rings while pyrimidines only have one ring .

Rawy Shaabana.k.a there is a phosphate group in between adjacent bases

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DNA in living cells is supercoiled.

This makes DNA very highly compact

Similar amounts of supercoiling exist in the DNA of bacterial and eukaryotic chromo-somes

The DNA found in mitochondria and chloroplasts exists in circular chromosomes that resemble those of prokaryotes

Both prokaryotes and plastids have circular genomes

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Rawy ShaabanThis picture is pretty much a tutorial on how to supercoil DNA.

The point of supercoiling DNA is to make it more compact.

Since we have to fit 3 billion genes in one tiny little cell, supercoiling DNA to make it more compact makes sense.

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Rawy ShaabanConvergent evolution -> they both evolved to be able to highly compact their DNA?

Knew BIOL1070 was useful after all!!!!1

First level of condensation - packaging DNA as a negative super coil into nucleosomes. This produces an 11 nm fibre.

The linker region is susceptible to digestion by an endonuclease.

DNA is wrapped around a nucleosome core of 8 histone proteins, and anchored by a 9th.

Second level of condensation - an additional folding or supercoiling of the 11 nm fibre to produce a 30 nm fibre. This is driven by nucleosomal interactions (histone H1 involved). To describe these structures, we have two models; solenoid and zig-zag.

The conformation of the 30 nm fibre depends on the methods used to visualize it.

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The 30 nm fibre is the basic structural unit of the metaphase chromosome (DNA in its most condensed form

Rawy ShaabanKNOW THIS SHIT

YOUR LIFE DEPENDS ON IT

all 3 levels

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Rawy ShaabanCondensation is the act of condensing something into something smaller

Rawy ShaabanThese balls are the nucleosomes core.

They are 146 nucleotide pairs wrapped around 8 histones

more on histones later

Rawy ShaabanThe non-ball part is called the linker region.

It is a bunch of DNA that varies in length from 8 to 114 nucleotide pairs.

Its job is to connect the balls together

Rawy Shaabanendo means insidenucle means nucleusase means enzymeTherefore, an endonuclease is an enzyme inside the nucleus.

Good job Rawy!

Rawy ShaabanThis 8 histone protein core is called an octamer, they just chill while wrapped in DNA.

The ninth guy (shown in green) comes in to seal the deal, completing the nucleosome.

Rawy ShaabanRemember that there are not two separate ways DNA is packaged at the 2nd level. Its just that we have two methods of being able to visualize it, which results in us seeing it in 2 different ways; solenoid and zigzag

Third level of condensation - attachment of the 30 nm fibre at many positions to a non histone protein scaold.

This completes the condensation and packaging of DNA into full chromosomes.

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Rawy Shaabanthird level:

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Rawy Shaabansecond levle:

Rawy Shaabanfirst level

Rawy Shaabanregular uncondensed DNA

Chromosomes4

Chromosome ends are protected by telomeres.

Telomeres resist degradation by DNases, prevent fusion of chromosomal ends, and facilitate replication of the ends of the linear DNA

Centromeres provide the point of attachment of chromosomes to microtubules in the mitotic spindle.

Yeasts centromeres are 110-120 base pairs long. There are three essential regions;

Region I and III are conserved sequences that bind proteins involved in spindle attach-ment. Region II is ~90 bp and over 90% of those are A or T bases.

Centromeres in multicellular eukaryotes are much larger and more complex.

i.e. 5000 to 15000 copies of the 171 bp alpha satellite sequence. Centromeres are also binding sites for a protein called CENP, which is related to histone H3.

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Rawy ShaabanThese guys chill on the ends of chromosome to protect them from being eaten by enzymes and to prevent them for merging together with other chromosome ends

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Rawy Shaabanmitotic spindle = all the spindle fibres that are used in mitosis.

before they start pulling on the chromosomes in metaphase, they need to attach to something. That something is centromeres

Functions of DNA:

The genotypic function - replication

The phenotypic function - gene expression

The evolutionary function - mutation

The transformation principle (Grith, 1928)

Mice injected with R bacteria --> remain alive

Mice injected with S bacteria --> died

Mice injected with dead S bacteria --> remain alive

Mice injected with R + dead S --> somehow died

The genetic material is DNA - part 1 (Avery, Macleod, McCarty, 1944)

R cells + S cell DNA + Protease --> S cell colonies (transformation)

R cells + S cell DNA + RNase --> S cell colonies (transformation)

R cells + S cell DNA + DNase --> No transformation

The genetic material is DNA - part 2 (Hershey & Chase, 1952)

Part 1:

Labeled proteins of page --> infect bacteria --> phage produced inside were unlabeled

Part 2:

Labeled DNA of phage --> infect bacteria --> phage produced inside were labeled.

Some viruses use RNA as their genetic material (Fraenkel-Conrat, 1957)

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Rawy Shaabanwhen we inject R cells in mice -> the mice stay alive (good)

when we inject S sells in mice -> the mice die (bad)

when we inject dead S cells -> the mice stay alive (good)

BUT SOMEHOW, when we put R cells with dead S cells together (which are both good), they end up killing the mice. How can this be?

Well, the dead S cells still have DNA inside them. What happened was the R cells picked up the S cell DNA from the dead S cells, and that transformed them into living S cells - which are bad so they kill the mice.

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Rawy ShaabanWhen we put in enzymes that digest proteins (proteases), the R cells still end up transforming into S cells

Rawy ShaabanWhen we put in enzymes that digest RNA (RNases), the R cells still end up transforming into S cells

Rawy ShaabanWhen we put in enzymes that digest DNA (DNases), The R cells no longer transform into S cells!!!

This means that, when you take DNA out of the picture, R cells cannot transform - which proves that DNA is in fact the genetic material

Rawy ShaabanPhages are viruses that kill bacteria.

They do this by injecting their DNA into bacteria, and hijack the cellular machinery to make little virus babies which pop out and burst the bacteria.

In part 1 of this experiment, they labelled the proteins in the phage. Then they looked at the virus babies, and found none of that labelled protein was there.

Rawy ShaabanIn part 2, this time, they labelled the DNA instead of the protein. When they examined the babies, they found that same labelled DNA, which means that the babies must have inherited it.

This further proves that DNA is the genetic material.

Mitosis5

Rawy ShaabanBeen doing mitosis since grade 9.. I got this shit

Cellular organelles and cytoplasmic contents get divided more or less equally between daughter cells. The endoplasmic reticulum and golgi complex are fragmented at the time of division and are reformed in the daughter cells. Mitochondria and chloroplasts are ran-domly divided between daughter cells. However, Nuclear chromosomes must be dupli-cated exactly and distributed equally to daughter cells.

Cell division goes through a set of stages called the cell cycle.

G1 phase (Gap 1) - growth, metabolism

S phase (Synthesis) - DNA replication (chromosome duplication)

G2 phase (Gap 2) - prepare for mitosis

M phase (mitosis) - divide + cytokinesis

Cells that are not actively cycling may exit the cell cycle from G1 and enter a state called G0. These cells are said to be quiescent.

There is no invariant clock that regulated the cell cycle timing in eukaryotic cells.

The centrosome cycle, in which centrioles are duplicated, progresses along with the cell cycle.

In animal cells, the centrosomes also function as microtubule organizing centers (MTOCs

Finally, when mitosis begins, each chromosome has already been duplicated.

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Rawy ShaabanBasically, chromosomes are the only thing that must be duplicated perfectly - dont fuck this up no matter what

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Rawy Shaabanjust chilling

Rawy ShaabanDuplicating chromosomes for mitosis

Rawy Shaabanjust chilling again

Rawy ShaabanThe centrosome cycle

Duplicated chromosomes at metaphase condense under the influence of condensin.

Model for the role of condensin and cohesion in the formation of mitotic chromosomes;

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Rawy ShaabanThis is an overview of mitosis. In a nut shell;

1. cell duplicates its chromosomes2. cell splits up in 2, producing identical diploid daughter cells

Rawy ShaabanRemember thesenumbersgood multiplechoice question

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1. Interphase

Duplicate chromosomes called sister chromatids joined at the centromere by cohesion.

The centrosome is duplicated.

2. Prophase

Initiation of spindle formation

Condensation of duplicated chromosomes

Fragmentation of ER and Golgi

Nucleolus disappears

Nuclear membrane breaks down

Spindle MTs invade nuclear space

2.5 Pro-metaphase

Chromosomal microtubules attach to kinetochores, which are on the outer surface of centromeres. Chromosomes move towards the equator of the spindle.

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Rawy ShaabanI said earlier that the spindle fibres attach to centromeres I LIED!!

It turns out that there are little protein complexes chilling on centromeres called kinetochores. This is where the spindle fibres actually attach teehee - prof Bendall (paraphrased btw)

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3. Metaphase

Duplicated chromosomes are aligned midway between spindle poles. This equatorial plane is called the metaphase plate.

4. Anaphase

Centromeres split and chromatids separate.

Chromosomes move towards opposite spindle poles, which are moving apart.

5. Telophase

Chromosomes cluster at opposite spindle poles.

Chromosomes become dispersed and decondense.

Nuclear envelope assembles around chromosomes

Golgi and ER reform.

Daughter cells form by cytokinesis

In plants, a membranous cell plate forms the scaold for a new, cellulose-containing cell wall.

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Rawy ShaabanNothing really to say on this page.. just know this shit

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Meiosis6

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Rawy ShaabanHomologues

Rawy ShaabanHeterologues

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Rawy ShaabanHomologues - same chromosome from different parents

Heterologues - different chromosomes

Rawy Shaabanthis guy is a protein structure that forms between two pairs of sister chromatids during meiosis to help with pairing

Rawy ShaabanCrossing over is when 2 chromosome (same chromosomes but from different parents) take pieces from each other. This results in two recombinant chromatids.

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Rawy ShaabanLeptonema

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Rawy ShaabanGood picture of this in page 14 of lecture notes, but its a pretty straight forward concept.

Rawy ShaabanAfter the first meiosis 1 division, the products arent actually sperms yet.

Spermatocytes still also have 23 sister chromatids. Actual sperms have 23 single chromatids

Oogenesis in mammals I

Oogenesis in mammals II

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Rawy ShaabanOogenesis only leads to the production of one final ovum, or egg cell, (in contrast to the four sperm that are generated from every spermatogonium).

Of the four daughter cells that are produced when the primary oocyte divides meiotically, three come out much smaller than the fourth. These smaller cells, called polar bodies, eventually disintegrate, leaving only the larger ovum as the final product of oogenesis.

In flowering plants, the sporophyte is the conspicuous part of the life cycle.

The gametophyte is much reduced and consists of just a few haploid cells in the anther and ovary of the flower.

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Rawy ShaabanBasically, plants are asexual so they have the equivalent of both sperm and egg cells inside them.

the sporophyte undergoes meiosis to form the gameteophyte, which produces sex cells (ova and pollen) by mitosis. The gametes combine to form a new sporophyte.

Mendelian Genetics7

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Rawy Shaabanwhen the parents reproduced, they produced the first generation which were all tall. When that generation reproduced, they produced 75% tall and 25% dwarf.

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Rawy ShaabanThis diagram shows how Mendels experiment in the previous page actually produced 75% tall and 25% dwarf in the second general, by using a punnett square

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Mendels Principle of Dominance: In a heterozygote, one allele may conceal the presence of another.

Mendels Principle of Segregation: Neither allele is typically changed by coexisting with the other in a heterozygote

Two dierent alleles segregate from each other during the formation of gametes

A dihybrid cross - are two traits inherited independently?

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Mendels Principle of Independent Assortment

The alleles of dierent genes assort/segregate independently of each other.

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Mendelian Predictions8

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Predicting the outcomes of a monohybrid cross with a Punnett square

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The chromosomal basis for Mendels principle of segregation

The chromosomal basis for Mendels principle of independent assortment

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Rawy ShaabanThis is why we can look at each allele separately

Predicting the outcomes of a dihybrid cross with a Punnett square

So, for 23 dierent genes, all on a dierent human chromosome, 2^23 = 8,388,608 dier-ent haploid gamete genotypes.

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The further apart two genes are on a chromosome, the more likely that they will assort in-dependently

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Rawy ShaabanGeneral rule:

or means addand or all means multiply

for example;

probabilty of being homozygous dominant OR heterozygous -> you add them

probability of being ALL three -> you multiply

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Rawy Shaabangood example

Since a heterozygote may have the same phenotype as the homozygous dominant, a test cross may be performed to determine the individuals genotype.

In a test cross, the individual of unknown genotype must be crossed with a homozygous recessive individual.

i.e. a test cross involving an individual of the genotype DD Gg Ww would involve crossing this individual to one with the genotype dd gg ww

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Pedigrees9

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Rawy ShaabanThis makes sense - dominant traits must appear at least once in each generation, otherwise they arent dominant

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Rawy Shaabanlook at the punnett square -> 1 of the 4 boxes is cc, hence the 1/4

Rawy Shaabanthe other 3 all have the dominant allele, hence the 3/4

Rawy ShaabanU stands for unaffectedA stands for affected

these are all the possible possibilities:

Rawy Shaabaninstead of doing this complicated shit, why not just use the equation on the next page -> much faster

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Rawy ShaabanWe know that R is not aa because it doesnt have albinism.This leaves three options: AA, Aa, and Aa (see punnett square)Out of those 3 options, the chances of R having a recessive a is 2/3

If R turns out to be a carrier, that means that it can either transmit A or a, making the chances that it will transmit a 50-50, or 1/2

Since S has albinism, that means it has aa - so there is 100% chance that it will transmit a because that is all she has

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Transcription & Translation

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Rawy ShaabanLots of pictures in this when.. *deep breath* here we go

An overview of Gene expression:

A gene is a transcribed region of DNA. Genes encode one of five known types of RNA;

RNA uses the pyrimidine uracil instead of thymine

The RNA pentose sugar is ribose, not a deoxyri-bose

The transfer of information from DNA to protein is a two step process in all organisms

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Rawy Shaabanribose has 1 more oxygen than deoxyribose

General features of RNA synthesis from a DNA template:

During transcription, the DNA double helix is locally unwound:

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Rawy ShaabanTemplate strand is the one that is copied

A typical promoter in E.coli:

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Rawy Shaabana promoter is a region of DNA that initiates transcription of a particular gene

A transcription terminator sequence in E.coli:

In prokaryotes, genes are closely spaced and several can be encoded on a single RNA molecule

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Rawy ShaabanThis is a specific sequence of bases that marks the end of a gene

Rawy Shaabanproducing multiple proteins from just one gene

Eukaryotes have additional levels of complexity; the primary transcript is processed and exported to the cytoplasm for translation:

The promoter of a eukaryotic protein coding gene

Unlike prokaryotic RNA polymerases, eukaryotic pols cannot initiate transcription on their own. A Transcription Factor is required to bind to the promoter to help assemble the transcription machinery.

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Rawy Shaabanthis guy is a protein that binds to specific DNA sequences, thereby controlling transcription

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Rawy ShaabanConsidered to be the core promoter sequence, the TATA box is the binding site of of transcription factors

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Rawy Shaabanto stop transcription:

1. enzyme cuts the strand of RNA.2. a 5 cap is added3. a tail of ~200 A bases is added at the end of the strand (3 end)4. introns are cut (spliced) out. - more on these coming up

Introns (intervening sequences) are non-coding sequences located between coding sequences. Introns are removed from the pre-mRNA and are not present in mature mRNA. Introns are variable in size and may be very large.

Exons (both coding and non-coding sequences) are composed of the sequences that re-main in the mature mRNA after splicing.

mRNA is an intermediate between DNA and protein.

In prokaryotes, an RNA sequence positions the ribosome to begin translation at the beginning of a coding sequence or open reading frame.

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Rawy ShaabanThe underlined nucleotides are most important, influencing the efficiency of translation by at least 10 fold if changed

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There are no spaces between codons; codons are adjacent

The genetic code is non-overlapping; each nucleotide is part of a codon

The genetic code is degenerate; most amino acids are specified by related codons

The genetic code is ordered; amino acids with similar properties are specified by related codons

The genetic code is ~universal; with minor exceptions, each triplet/codon has the same meaning in all organisms

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Rawy ShaabanAbout the genetic code;

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Mutations11

Mutations can arise spontaneously, as a result of an error during DNA synthesis . This can be due to the incorporation of rare isoforms of the four bases that have altered base pairing properties, or due to the inherent fallibility of replication proteins.

The nitrogenous bases of DNA exist in two isoforms (tautomers). These rare isoforms have altered base pairing properties. Incorporation of a rare isoform during DNA replication can lead to a change in DNA sequence.

Mutations of DNA in the germ line (i.e. during the mitotic divisions of spermatogonia or oo-gonia) will be inherited. Hot spots for spontaneous mutations during DNA replication in-clude; simple repeats, symmetrical repeats, and palindromes.

Mutations can also be induced by exposure to chemical mutagens. Chemical mutagens can be divided into two groups;

Those that are mutagenic only to replication DNA (base analogues, acridine dyes), and those that are mutagenic to both replication and non-replicating DNA (akylating agents).

Mutations can also be induced by exposure to radiation. Adsorption of UV energy by py-rimidines results in their dimerization.

Gene mutations can aect the encoded proteins. The eects of a single base mutations vary enormously.

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Rawy Shaabandifference between symmetrical repeat and palindrome is that symmetrical repeats are just inverted repeats of each other.

on the other hand, palindromes become exactly identifcal if you reverse one of them. Kind of like if you spell racecar backwards, you get racecar.

^ Excellent analogy, good job Rawy!!

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A single base change in the beta globin gene causes sickle cell anemia:

Acridines intercalate between adjacent base pairs and distort the double helix.

When these molecules replicate, additions and deletions of one to a few base pairs occur.

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Rawy Shaabanchance one little T to one little A and you get sickle cell anemia

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Rawy ShaabanThis shifts the entire code by +1 or -1, which potentially changes every single amino coming after the mutation

Expanding genes - At least 15 human inherited disorders result from expanding triplet/trinucleotide repeats. Usually

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Rawy Shaabanmost are common sense but review them any way

Rawy Shaabanwhen different amino acids are coded, the proteins shape ends up being different - which could make it dysfunctional. This protein becomes useless

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Allele Variation & Gene Function

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Incomplete Dominance: heterozygotes (with one copy of the dominant allele) have half the functional gene dosage.

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Rawy Shaabani.e. both alleles are capital letters

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Rawy ShaabanThis is an example of a gene doing more than one thing.

The Ay gene doesnt kill the Yellow mice who have an A+, but kills the embryo which has another Ay

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Rawy ShaabanAll offspring end up being wildtype.The defect in s is complimented by the wildtype allele from cinnabar and vice versa.

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Rawy ShaabanIn a nut shell, complementation occurs when two strains of an organism with different homozygous recessive mutations that produce the same phenotype end up producing offspring with the wild-type phenotype

From Genotype to Phenotype

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Rawy Shaabani.e. temperature, soil, pH

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Rawy Shaabani.e. rest of genome

Rawy ShaabanConditional alleles just means that how the alleles behave depends on what their environment is like

Rawy ShaabanLike the Walking Dead everyone is infected but they only become zombies under certain conditions (i.e. when theyre dead).

Beautiful example.. nice one Rawy!!

Rawy Shaabanthese conditions trigger the anemia

Rawy Shaabanphenylalanine hydroxylase loses its function so we get a build up of phenylpyruvic acid which is toxic :(

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Rawy Shaabanthis is a gene that affects multiple traits.. most genes are actually pleiotropic

Rawy ShaabanLook at the circled part of this pedigree

Incomplete penetrance is when children are infected but the parents arent - even though the disease is supposed to be dominant.

This is due to some other combination of genes that influence the disease gene and make it different

This is an example of how the internal environment affects gene expression

Rawy ShaabanThis is when the same allele shows a variation in phenotypes. In this case, the variable effect is the range of eye size, from very small (pretty much not there) to huge.

This is also due to the internal genetic environment, but it could be external too

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Rawy Shaabanwalnut is the ugliest

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Rawy ShaabanDont confuse this with dominant alleles overriding recessive alleles

Epistasis is when ONE ENTIRE GENE completely overrides ANOTHER ENTIRE GENE

Rawy ShaabanAs long as theres one dominant C or one dominant P, its purple.

If there are 2 pps or 2 ccs, it becomes white. These recessive alleles team up and override the dominant one

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Gene Regulation14

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Rawy Shaaban~Fin

Rawy ShaabanReferences:

1. Dr. A. Bendall BIOL*1090 Lecture Notes 2. P. Snustad and M. Simmons Principles of Genetics Textbook

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