LECTURE 12/11

cell grows in preparation for cell division, chromosomes are duplicated with genetic material copied precisely

chromosome copies are separated from each other and moved to opposite sides of the cell

the cell divides into two daughter cells, genetically identical to each other and the parent cell.

a complex of dna and protein that condenses during cell division

(nonreproductive cells) have two sets of chromosomes

reproductive cells (sperm and eggs) have half as many chromosomes as somatic cells

• dna is replicated and chromosomes condense • each duplicated chromosome has two sister chromatids • centromere (‘waist’) of the duplicated chromosome where two chromatids are most closely attached • two sister chromatids of each duplicated chromosome separate and move into two nuclei • Once separate, the chromatids are called chromosomes

G1- metabolic activity and growth G2- metabolic activity, growth, and preparation for cell division S- metabolic activity, growth and dna synthesis

prophase- metaphase- anaphase- telophase-

in. early prophase I, each chromosome pairs with its homolog and crossing over occurs. X-shaped regions called chiasmata are sites
of crossovers nonsister chromatids are broken at precisely matching points A zipper-like structure called the synaptonemal complex holds the homologs together tightly During synapsis, DNA breaks are repaired, joining DNA from one nonsister chromatid to the corresponding segment of another

In metaphase I, pairs of homologs line up at the metaphase plate, with one chromosome facing each pole Microtubules from one pole are attached to the kinetochore of one chromosome of each pair Microtubules from the other pole are attached to the kinetochore of the other chromosome

in anaphase I, pairs of homologous chromosomes separate One chromosome of each pair moves toward opposite poles, guided by the spindle apparatus Sister chromatids remain attached at the centromere and move as one unit toward the pole

In the beginning of telophase I, each half of the
cell has a haploid set of duplicated chromosomes Each chromosome still consists of two sister chromatids

made of microtubules that control chromosome movement during mitosis. in animal cells assembly of spindle microtubules begin at the centrosome

prokaryotes. chromosome replicates and the the daughter chromosomes actively move apart. plasma membrane pinches inward dividing the cell into two

units of heredity, made up of dna segments

a single individual passes all its genes to its offspring w/o gamete fusion

an individual/group of genetically identical individuals from the same parent

2 parents give rise to offspring that have unique combinations of genes from the inherited parents

2 chromosomes in a pair. One from each parent.

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union of gametes (sperm and egg)

fertilized egg, one set of chromosomes from each parent

homologous chromosomes are separated. haploid cells with duplicated chromosomes.