chromosomal basis of inheritance cell division – mitosis and meiosis
TRANSCRIPT
Chromosomal basis of inheritance
cell division – mitosis and meiosis
double helix
nucleosomes
chromosome (metaphase)
‘supercoil’
DNA is normally dispersed in cell; condensed prior to cell division
Location of DNA in cells:
Chromosomes
structure: two chromatids connected at the centromere
• each species has a characteristic set of chromosomes• individual chromosomes vary in size and shape• number and size is unrelated to complexity of organism
karyotype
Chromosomes
Mitosis – cell replication
interphase prophase metaphase anaphase telophase
Mitosis – cell replication
interphase: DNA replication occurs to produce double-chromatid chromosomes
prophase: DNA condenses
metaphase: chromosomes align in center of cell
anaphase: chromatids separate, move toward opposite poles
telophase: nuclear membranes reform; cell splits into two (cytokinesis)
Meiosis – cell division with chromosome # reduction
reductional division
equationaldivision
interphase prophase I metaphase I anaphase I
metaphase II anaphase II
telophase II
crossing-over
Meiosis – cell division with chromosome # reduction
Segregation of chromosomes
Meiosis I
Meiosis II
Oogenesis vs. spermatogenesis
sperm – many, with small cellular investment mitochondria rarely transferred to zygote
ova – few, with large cellular investment many mitochondria inherited
Oogenesis vs. spermatogenesis
sperm – many, with small cellular investment mitochondria rarely transferred to zygote
ova – few, with large cellular investment many mitochondria inherited
(remember mitochondrial DNA?)
polar bodies (3)
• each species has a characteristic set of chromosomesN = number of unique chromosomes (haploid number)2N = number of chromosomes in somatic cells of diploid species
• number and size of chromosomes is unrelated to complexity of organism (e.g., nematode N varies from 1 to 48)
Chromosomes