
<ul>
  <li>
    Each cell has extranuclear chromosomes within mitochondria (about 10 single circular
    chromosomes)
  </li>
  <li>0.5% of total DNA</li>
  <li>These replicate independently of the nuclear genome</li>
  <li>This DNA has no introns</li>
  <li>
    Genes encode for tRNA and ribosomal RNA required for mitochondrial protein synthesis and
    proteins involved in cellular oxidative phosphorylation
  </li>
  <li>Mitochondrial DNA has a higher mutation rate than nuclear DNA</li>
  <ul>
    <li>The DNA polymerases here are highly inaccurate</li>
    <li>Mitochondrial DNA is much more susceptible to oxidative damage</li>
    <li>Alkylating agents affect mtDNA much more effectively</li>
    <li>Repair mechanisms are underdeveloped for mtDNA</li>
    <li>With no introns, mutations are likely to impact a coding sequence</li>
  </ul>
  <li>
    Sperm lose their acrosome during fertilisation (they are rich in mitochondrial DNA before this)
  </li>
  <li>Therefore mitochondrial chromosomes are inherited exclusively from the female ova</li>
  <ul>
    <li>Males cannot transmit</li>
    <li>Both males and females can be affected if their mother has the defective gene</li>
    <li>
      An affected mother passes the defect to <strong>all </strong>her children but only daughters
      will transmit
    </li>
  </ul>
  <li>
    Mitochondrial DNA is distributed between several mitochondria in a cell, therefore normal and
    abnormal DNA can coexist: so-called heteroplasmy
  </li>
  <ul>
    <li>
      The proportion of abnormal DNA needed to produce a disease phenotype creates the
      &ldquo;threshold effect&rdquo;
    </li>
    <li>Disease severity is therefore variable and some children may not be manifestly affected</li>
  </ul>
</ul>
<HotTopic>
  <p>Mitochondrial diseases</p>
  <ul>
    <li>Leber&rsquo;s hereditary optic neuropathy</li>
    <li>Kearns-Sayre syndrome</li>
    <li>MIDD (maternally inherited diabetes mellitus and deafness)</li>
    <li>MELAS</li>
    <li>Myoclonic epilepsy with ragged red fibre</li>
    <li>Zidovudine induced acquired mitochondrial myopathy</li>
  </ul>
</HotTopic>


Genetics

Mitochondrial Inheritance

Intro

FRCOphth Part 1 Study Notes

Orbit and ocular adnexae

Orbit

Extraocular Muscles

Orbital Blood Vessels

Paranasal Sinuses

Lacrimal Glands

Tear Film

Eyelids

Blinking

Anterior segment - ocular surface

Conjunctiva

Conjunctivitis

Sclera

Cornea

Corneal Structure And Development

Corneal Physiology

AC to Lens

Angle

Ciliary Body

Aqueous Humour Dynamics

Iris

Pupil

Lens

Posterior segment

Choroid

Vitreous

Retinal Macrostructure

Neurosensory Retina

Retinal Pigment Epithelium

Neuroanatomy

Venous Sinuses

Cerebral Ventricles

Cerebral Blood Supply

Supranuclear Gaze Pathways

Head And Neck Autonomic Nervous Supply

Head And Neck Glands

Osteology

Nerves

Muscles And Pharyngeal Arches

Extraocular Nerves

Sensory Nerves

Physiology

Physics Of Blood Flow

Neuronal Control Of Blood Vessels

Oxygen-Haemoglobin Dissociation Curve

Cytochrome p450

Pituitary Gland

Thyroid Hormone Production

Insulin

Glucagon

Parathyroid Hormone

Corticosteroids

Catecholamines

Cardiac Cycle

Renal Physiology

Fluid Balance

Acid-Base Balance

Muscle Physiology

Sensory Fibres

Cutaneous Receptors

Endocytosis

Glycosaminoglycans

Condensed Ocular Biochemistry

Eye Movements

Accomodation

Vision

Visual Cycle And Phototransuction

Visual Pathway

Visual Acuity

Colour Vision

Binocular Vision

Pathology

Collagen

Tissue Damage

Inflammation

Disease Entities

Wound Healing

Thrombosis / Atherosclerosis

Cell Growth

Neoplasia

Histopathology

Nystagmus

Free Radicals And Antioxidants

Immunology

Ocular Immunology

Microbiology

Viral Infections

Bacterial Infections

Fungal Infections

Protozoa

Nematodes

Antimicrobials

Chromosomes

Mitosis

Meiosis

Genes

Polypeptide Synthesis

Histones

MicroRNA

Hardy-Weinberg Equilibrium

Mutations

Chromosome Defects

Autosomal Inheritance

X-Linked Inheritance

Multifactorial Inheritance