Gene expression. Have you ever wondered how a frog grows? http://www.teara.govt.nz/en/frogs

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  • Gene expression

  • Have you ever wondered how a frog grows?

  • Native male frogs sit on the eggs and the young froglets hatch almost fully formed.

  • Why are their parts where they are?

  • The answers lie in their cells.

  • In particular the answer can be found in their genetic material.A right handed helix

  • Lets revisit how we know that DNA is important.Streptococcus pneumoniaeS: smooth(virulent)R: rough(avirulent)

  • DNA is the genetic material - Griffith 1928

  • Avery, MacLeod & McCarty 1944Chemically characterised the transforming extract from virulent cells observed by GriffithRemoved the protein from transforming extract and it still transformedRemoved RNAextract still transformedRemoved DNAprevented transformationTherefore transforming substance was DNABiochemically characterised the transforming extract, all its properties were consistent with DNA:High Mw (centrifugation)High charge (electrophoresis)Characteristic UV absorbanceChemical analysis, ratio of nitrogen to phosphorus

  • Hershey-Chase 1952Left, T2 virus protein radioactively labelled 35SRadioactivity outside

    Right: T2 virus DNA radioactively labelled 32PRadioactivity inside

    THEREFORE genetic material infecting E.coli was DNA and not protein

    Genes are made from DNA (except some RNA viruses)

  • Genes are encoded within DNA

  • What is a gene?Classical molecular gene: A stretch of DNA sequence that codes for a particular protein that has a particular function.(10,11) This can be an interrupted sequence within a chromosome.

  • *The gene concept has changed over time

  • *Evolutionary gene: any portion of chromosomal material that potentially lasts for enough generations to serve as a unit of natural selection.(39) As such a gene is an inherited unit which is somewhere between a nucleotide and a chromosome.

    Systemic Concept:The gene is a combination of (one or more) nucleic acid (DNA or RNA) sequences, defined by the system (the whole cell, interacting with the environment, or the environment alone, in sub-cellular or pre-cellular systems), that gives origin to a product (RNA or polypeptide).(57)Other definitions of a gene

  • The central dogma(Genotype)(Phenotype)

  • http://vcell.ndsu.nodak.edu/animations/transcription/advanced.htmTranscription is the first step in the process.

  • How many genes does it take to make a person?20,000-25,00026,00019,00013,0006,0004,000

  • *DSCAM: one gene 38,016 mRNAsAn immunoglobulin (Ig) superfamily memberan axon guidance receptorDrosophila melanogaster Dscam gene contains 115 exons spanning ~60,000 bp20 exons are constitutively spliced (open boxes) and 95 exons are alternatively spliced (shaded boxes).Alternatively spliced exons are orgnized into 4 clusters (exons 4,6, 9, 17) that contain 12, 48, 33 and 2 alternative exons each.Exons in each cluster are spliced in a mutually exclusive manner.

    Celotto & Graveley 2001 Genetics 159:599-608

  • *Immunoglobulin genes recombine within the DNA.

  • So what if nuclei are the wrong shape?85 mm16 mm

  • More or less matters!EdwardsPatauKlinefelters(XXY)Turners(X)

  • *Albert Einstein (1955)

  • *30-35% of cells are aneuploid~4% aneusomy for chr 21Affects survival, proliferation potential, and protein imbalances

  • *Falchi et al. (2014) Nat Genetics 46:492-498 Copy number affects your weight

  • How big is a vertebrate cell?http://medicalpicturesinfo.com/human-cell/

  • *Progeria (Hutchinson-Gilford progeria) Children with this disease typically have a stroke or heart attack caused by severe atherosclerosis at an average age of 13 years.

  • Nuclei in Progeria are the wrong shape.

  • Shape directly affects the genes that are turned on.31 of the altered genes affect vasculature and atherosclerosis 22 of the altered genes affect skeletal, limb and cartilage

  • Defects in transcription can cause problems. Who amongst us is lactose intolerant?

  • LCT gene 17 exons Chr 2q21Lactase is encoded by a single gene

  • Swallow; Annu Rev Genet 2003:37197-219The frequency of lactase persistence varies dramatically in different populations.

  • Swallow; Annu Rev Genet 2003:37197-219Pastoralists and milk drinkers tend to have higher frequencies of lactase persistence than nonpastoralists

  • Translation is important too.

  • tRNA: the adapter

  • What is the genetic code?Redundant codons are all synonyms for the same protein building block.Degenerate codons differ in their third positions; e.g. both GAA and GAG code for the amino acid glutamic acid.

  • SerCandidaNons.MicrococcusNons.MicrococcusNons.MycoplasmaTrpMycoplasmaSpiroplasmaCysEuplotesGln: Ciliates & AcetabulariaThe genetic code is not always the same

    First position (5 end)

    Second Position

    Third position (3 end)

    U

    C

    A

    G

    U

    UUU Phe

    UCU Ser

    UAU Tyr

    UGU Cys

    U

    UUC Phe

    UCC Ser

    UAC Tyr

    UGC Cys

    C

    UUA Leu

    UCA Ser

    UAA Stop

    UGA Stop

    A

    UUG Leu

    UCG Ser

    UAG Stop

    UGG Trp

    G

    C

    CUU Leu

    CCU Pro

    CAU His

    CGU Arg

    U

    CUC Leu

    CCC Pro

    CAC His

    CGC Arg

    C

    CUA Leu

    CCA Pro

    CAA Gln

    CGA Arg

    A

    CUG Leu

    CCG Pro

    CAG Gln

    CGG Arg

    G

    A

    AUU Ile

    ACU Thr

    AAU Asn

    AGU Ser

    U

    AUC Ile

    ACC Thr

    AAC Asn

    AGC Ser

    C

    AUA Ile

    ACA Thr

    AAA Lys

    AGA Arg

    A

    AUG Met

    ACG Thr

    AAG Lys

    AGG Arg

    G

    G

    GUU Val

    GCU Ala

    GAU Asp

    GGU Gly

    U

    GUC Val

    GCC Ala

    GAC Asp

    GGC Gly

    C

    GUA Val

    GCA Ala

    GAA Glu

    GGA Gly

    A

    GUG Val

    GCG Ala

    GAG Glu

    GGG Gly

    G

  • Some people cant use Glucose.Typically they have mutations in GLUT1*These mutations occur because the codons are changed.

  • GLUT1 mutations are often in helix 4*

  • Mitochondria in a mouse myoblast cell*Image taken by James Markworth (Liggins Institute)Mitochondria are red

    Actin filaments are green

    Nucleus is blue

  • *Differences in the human nuclear and mitochondrial genetic codesMetTrpStop

    First position (5 end)

    Second Position

    Third position (3 end)

    U

    C

    A

    G

    U

    UUU Phe

    UCU Ser

    UAU Tyr

    UGU Cys

    U

    UUC Phe

    UCC Ser

    UAC Tyr

    UGC Cys

    C

    UUA Leu

    UCA Ser

    UAA Stop

    UGA Stop

    A

    UUG Leu

    UCG Ser

    UAG Stop

    UGG Trp

    G

    C

    CUU Leu

    CCU Pro

    CAU His

    CGU Arg

    U

    CUC Leu

    CCC Pro

    CAC His

    CGC Arg

    C

    CUA Leu

    CCA Pro

    CAA Gln

    CGA Arg

    A

    CUG Leu

    CCG Pro

    CAG Gln

    CGG Arg

    G

    A

    AUU Ile

    ACU Thr

    AAU Asn

    AGU Ser

    U

    AUC Ile

    ACC Thr

    AAC Asn

    AGC Ser

    C

    AUA Ile

    ACA Thr

    AAA Lys

    AGA Arg

    A

    AUG Met

    ACG Thr

    AAG Lys

    AGG Arg

    G

    G

    GUU Val

    GCU Ala

    GAU Asp

    GGU Gly

    U

    GUC Val

    GCC Ala

    GAC Asp

    GGC Gly

    C

    GUA Val

    GCA Ala

    GAA Glu

    GGA Gly

    A

    GUG Val

    GCG Ala

    GAG Glu

    GGG Gly

    G

  • *Protein structure is important as well.

  • *Prions and Alzheimers disease are examples of pathological protein misfolding

  • *

  • Whats different between these bears?

  • Polar bears and Brown BearsDivereged ~479-343 kya

  • Polar bears are adapted to high fat dietsModified from Liu et al. Population genomics reveal recent speciation and rapid evolutionary adaptation in Polar bears. Cell (2014): 157, 785-794 and Ombostad, I. (2012) Relationships between persistent organic pollutants (POPs) and plasma clinical-chemical parameters in polar bears (Ursus maritimus) from Svalbard, Norway. Student thesis (Trondheim, Norway: Norwegian University of Science and Technology).

  • The environment is affecting the genes that Polar bears have.

  • Polar bears have seven missense substitutions in the LYST gene

  • Chediak-Higashi syndrome Autosomal recessiveMutation of lysosomal trafficking regulator (LYST)

  • What do Chimo and a Polar bear have in common?

  • Lyst affects melanosome maturation

    The organelle that is involved in synthesis, storage and transport of melanin

  • White fur is common in the arctic:

    beluga whales, polar bears, arctic hare, arctic fox but not all due to Lyst mutations.

    Confers a selective advantage?

  • www.katoa.ac.nz Hands on experience for you and your students! justin.osullivan@auckland.ac.nz.

    Maud Island frog. Maud Island frog. It is found only on Maud Island (over 10,000 frogs) and Motuara Island, in the Marlborough Sounds.FeaturesNew Zealands frogs belong to an ancient and primitive family, and do not exist anywhere else. They have evolved in unique ways. Their eyes are round, not slit, and they catch insects with their mouth, not a tongue. They have an extra vertebra, but no eardrums and they dont croak.HabitatOnly Hochstetters frogs live near water. The other species keep damp in moist, shady places in the forest or amongst rocks. During the day they hide under logs, stones and bushes