phase1
Rhona, Tom, Emily
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• Cover basic information form IMMS• Cover things likely to come up in exams• Look at areas where there is often confusion
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aims
• Cells• Homeostasis• Molecular Building Blocks• DNA and RNA• Mitosis and Meiosis • Genetic Diseases
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introduction
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Cells
• Microtubules- tubulin• Microfilaments- Actin• Intermediate filaments- desmosomes
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Cytoskeleton
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Membrane- Phosholipids:- Sphingophospholip
ids- Glycerophospholipi
ds- Cholesterol-
membrane fluidity and signalling system
- Glycolipids
• Physical boundary• Regulation of substance movement• Receptors for cell to cell signalling• Attachment to extracellular matrix
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Function of cell membrane
• Receptors• Enzymes• Transport proteins• Cell adhesion molecules
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Membrane proteins
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Movement across membrane
• Control of internal body environment • Autocrine• Paracrine• Endocrine
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Homesostasis
• 60% of body weight 40 intracellular 20 extra• Extracellular: interstitial, plasma, transcellular
(digestive)• Regulation: Vasopressin
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Water
• Osmosis: is the spontaneous net movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration
• Osmolality: The amount of solute in a solution• Oncotic pressure: Pressure exerted on water
movement by solute
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Definitions
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Molecular building blocks
• Primary: linking of amino acids• Secondary: alpha helix's, beta sheets (H
bonds) • Tertiary: Interactions between side chains• Quaternary: joining of polypeptides
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Protein structures
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DNA and RNA
Degenerate
Almost universal
Unambiguous
Non-overlapping
Features of DNA
Semi-conservative
Enzymes:•Topoisomerase•Helicase•DNA polymerase•DNA ligase
Okazaki fragments
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DNA Replication
Transcription and Translation
Nucleus
DNA (gene)
mRNA
mRNA
Protein
Ribosome
Transcription
Translation
Introns are non-coding regionsExons are coding regions
Introns and Exons
Start codon: AUGStop codons: UAG, UGA, UAA
Single nucleotide polymorphism can result in…•Mis-sense: Codes for a different aa•Non-sense: Doesn’t code for an aa. Acts as a stop codon
Codons and mistakes
Mitosis: Cell division in which two identical daughter cells are produced
Mitosis and Meiosis
Meiosis: Cell division in which the chromosome number is halved
Mitosis: Cell cycle
PMAT
Prophase(Prometaphase)Metaphase AnaphaseTelophase
Mitosis: Stages
Prophase: Chromatin condenses to chromosomes
Prometaphase: Nuclear membrane disintegrates. Chromosomes attach to microtubules
Mitosis: Stages
Metaphase: Chromosomes line-up on equatorial plate
Anaphase: Sister chromatids are separated and pass to opposite poles
Mitosis: Stages
Telophase: Nuclear membranes form, chromosomes unfold
Cytokinesis: Cell divides
Mitosis: Stages
Mitosis under the microscope
Meiosis
PMA(T) X2
Meiosis 1•Where chromosome number is halved•Crossing-over between non-sister chromatids (M1)
Meiosis 2•Sister chromatids separate•Haploid cells produced
Genetic diversity •Crossing over between non-sister chromatids •Random assortment on metaphase plate
Meiosis
Gametogenesis
Gametogenesis: Formation of haploid gametes in precursor cells (in testes/ovaries)
Differences between sexes:•Male: Meiotic division starts at puberty•Female: Meiosis 1 completed at ovulation, Meiosis 2 if fertilisation occurs
Gametogenesis
Mendel's second law (Law of independent assortment):
Alleles of one gene sort into gametes independently of the alleles of another gene
Gonadal Mosaicism
Gonadal mosaicism: mutation in primordial germ cell. All gametes from it are affected
Mother
• Phenotype = The appearance of an individual resulting from interaction of the environment and genotype
• Genotype = The genetic constitution of an individual
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Genetic Diseases
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Autosomal Dominant • Manifests in heterozygous
state • Both males and females are
effected equally • 50% chance of inheriting
disorder • e.g. Achondroplasia, Marfan
syndrome, Huntington’s disease
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Sex Linked • Males = XY Females = XX• X linked genes never pass from father to son• Males can never be carriers
X linked Dominant: •Expressed and transmitted by both sexes •Occurs twice as frequently in females as males•Difficult to distinguish from AD•e.g Hypophostphataemia rickets
X linked Recessive :•More males than females show the phenotype •Affected male would usually have no effected offspring but all the daughters would be carriers •e.g Haemophilia, Duchenne muscular dystrophy
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Sex Linked
• Process of x chromosome inactivation • One of the two X chromosomes in every cell in
a female is randomly inactivated early in embryonic development.
• Via methylation
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Lyonization
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Knudson’s 2 Hit Hypothesis
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Multifactorial Disease
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Quiz Time
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Quiz Time
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Quiz Time
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The end!Thank you for listening!
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