IMMS Flashcards
What is the purpose of mitosis?
Makes 2 genetically identical daughter cells
Growth
Replaces dead cells
Describe prophase and metaphase
- Prophase: chromatin condenses into chromosomes, centrosomes nucleate microtubles and move to opposite poles of nucleus
- Pro metaphase: nuclear membrane breaks down, chromatids attach to microtubules
- Metaphase: chromosomes line up at equator
Describe anaphase and telophase
After metaphase:
- Anaphase: sister chromatids separate to opposite poles
- Telophase: nuclear membranes reform, chromosomes uncoil to chromatin, cytokinesis starts
Key points of meiosis
- 4 haploid daughter cells
- genetically different, for diversity
- 2 cell divisions
- only in gametes
- crossing over in prophase 1
Describe spermatozoa production
-Primordial germ cells undergo lots of mitoses to produce spermatogonia
-Meiosis begins at puberty
-Equal cytoplasm division, 4 gametes
-Millions constantly produced
-Takes 60-65 days
Describe egg production
-Primordial germ cell undergoes 30 mitoses to form oogonia
-Oogonia enter prophase of meiosis I by 8th month of intrauterine life, suspended
-Cells enter ovulation 10-50 years later
-Cytoplasm divides unequally – 1 egg and 3 polar bodies (that apoptose)
-Meiosis I is completed at ovulation
-Meiosis II only completed if fertilisation occurs
How does DNA coil into chromosomes?
-DNA winds around histones forming nucleosomes
-Nucleosomes coil into chromatin
-Chromatin coils into supercoils and chromosomes
What is euchromatin?
Actively transcribing cellular DNA
light staining
What is heterochromatin?
Transcripitionally inactive cellular DNA
Dense staining often adjacent to nuclear membrane
Highly condensed
What are the main parts of a chromosome?
P- short top arm
Q- long arm
Centromere- controls movement in division
Telomere- at tip, seals chromosome
Describe G-banding in chromosomes
Treated with trypsin
Stained with Giesma DNA-binding dye
Gives light and dark bands
What is the clinical relevance of cell division?
- Detecting chromosomal abnormalities
- Categorising tumours as B/M
-Grading M tumours
What is nondisjunction?
Failure of chromosome pairs to separate in meiosis 1 or
Failure of sister chromatids to separate in meiosis 2
What is gonadal mosaicism?
Occurs when precursor germ line cells are a mixture of two or more genetically different cell lines
One cell line is healthy, one is mutated
Increases with parent’s age
Examples of gonadal mosaicism
More common in autosomal dominant or x linked
Osteogenesis imperfecta
Duchenne muscular dystrophy
Clinical relevance of mitotic spindle (drugs)
Taxol
Vinca alkaloids
Spindle poles- ispinesib
Clinical relevance of anaphase
Colchicine like drugs
Anagram for recognising rare disease
G - group of congenital abnormalites
E- extreme presentation of common conditions
N- neurodevelopmental disease/ early onset NG
E- extreme pathology
S- surprising lab results
What are constitutional chromosomal abnormalities?
Present from birth
Occurs at gametogenesis
Affects all cells
Heritable
What are acquired chromosomal abnormalities?
Changes occur during lifetime
Restricted to malignant tissue
Not heritable
What are fusion genes?
Breakpoints occur within two genes
Hybrid gene created
Chimaeric protein
What is gene deregulation?
Juxtaposition of gene to regulating gene
Altered regulation result in increased transcription and neoplastic growth
Define genotype
Genetic constitution of an individual
Define phenotype
appearance of individual (physical, biochemical, physiological) which results from interaction of genotype and environment