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