Phase1 Rhona, Tom, Emily The Peer Teaching Society is not liable for false or misleading...

phase1

Rhona, Tom, Emily

The Peer Teaching Society is not liable for false or misleading information…

• Cover basic information form IMMS• Cover things likely to come up in exams• Look at areas where there is often confusion

• Cells• Homeostasis• Molecular Building Blocks• DNA and RNA• Mitosis and Meiosis • Genetic Diseases

introduction

• Microtubules- tubulin• Microfilaments- Actin• Intermediate filaments- desmosomes

Cytoskeleton

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

Function of cell membrane

• Receptors• Enzymes• Transport proteins• Cell adhesion molecules

Membrane proteins

Movement across membrane

• Control of internal body environment • Autocrine• Paracrine• Endocrine

Homesostasis

• 60% of body weight 40 intracellular 20 extra• Extracellular: interstitial, plasma, transcellular

(digestive)• Regulation: Vasopressin

• 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

Definitions

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

Protein structures

DNA and RNA

Degenerate

Almost universal

Unambiguous

Non-overlapping

Features of DNA

Semi-conservative

Enzymes:•Topoisomerase•Helicase•DNA polymerase•DNA ligase

Okazaki fragments

DNA Replication

Transcription and Translation

Nucleus

DNA (gene)

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

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

Genetic Diseases

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

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

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

Lyonization

Knudson’s 2 Hit Hypothesis

Multifactorial Disease

Quiz Time

The end!Thank you for listening!

We are happy to answer any questions by email/arrange to meet:TAtkinson2@sheffield.ac.uk

rmcmillan1@sheffield.ac.uk

Phase1 Rhona, Tom, Emily The Peer Teaching Society is not liable for false or misleading...

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