Chromosomes, cell division, meiosis and chromsoome abnormalities Flashcards
Telomere
Protect ends and prevent erosion
Centromere
Join sister chromosomes which are held together with cohesins until anaphase
Site of kinetochore and non coding satellite DNA
Repeats 5’ - TTAGGG-3’ (10-15kb)
Kinetochore
Protein complex on centromere where microtubule attaches
How to get over shortening chromosomes
Enzyme telomerase adds DNA using RNA as lose bases after every mitosis
S phase
replication
G1
Cell growth
G2
Cell divide
Interphase
G1, S , G2
M phase
Prophase, metaphase, anaphase , telophase and cytokinesis
Prophase
Spindle from centriole and nuclear membrane breakdown
Metaphase
Chromosomes replicated and align on M plate where spindle attaches
Anaphase
Sister chromosomes separate and move to opposite poles
Telophase
Reform nuclear membrane
Cytokinesis
Cytoplasm separates
Nucleosome
Negative DNA and positive histone protein => solenoid
Why package DNA?
DNA neutralised and takes up less space
Inaccessible until required
Metacentric
Similar p and q length
Submetacentric
Slightly offset
Acrocentric
Q much larger than p and no coding DNA
FISH
Look for specific area of interest in karyotype
Label with fluorescent dye
What can FISH be used for
Centromeric - chromosome number
Telomeric, unique sequence or whole chromosome differences
Meiosis
Diploid => haploid
Recombination occurs => genetic diversity
Oogenesis
Egg formation 10-50 years
20-30 mitoses and 1 egg with 3 polar bodies
Spermatogenesis
60-65 days so more chance of mutation
4 spermatids and 100-200 million per ejaculate
Do mitochondria come from only mum or dad?
Mum
What is a barr body?
X inactivation occurs in females and the barr body is the inactive x chromosome
