Reproduction & Development

Spindle

________ fibres attach to centromeres only on exposed sides.

original number of chromosomes

When an ovum is fertilized by a sperm, the ________ (46= 2n) is restored, forming a zygote.

G2

________ (second cell growth stage): rebuilds energy reserves and prepares for mitosis.

Humans

________ have 23 pairs of chromosomes (46 chromosomes total)

Growth Differentiation

________: Mitosis enables organisms to grow from a single- celled zygote into a mature organism that might contain hundreds of trillions of specialized cells.

DNA strands

________ shorten and thicken, causing chromatin to condense into visible chromosomes.

Homologous pairs

________ move to centre → centromeres on either side of equator.

Chromosomes

________ do not uncoil to form chromatin.

DNA Molecule

________: two sugar- phosphate backbones with nitrogen base "rungs.

Chromatids

________ move to opposite poles of cell (same number of single- copy chromosomes should be at each pole)

Gametes

________ (sperm or eggs) are haploid cells.

somatic cells

All ________ contain homologous pairs of chromosomes.

Centrioles

________ separate and move to opposite poles of cell.

life cycle

The ________ of all sexually reproducing organisms alternates between haploid and diploid cells.

Histones

________: DNA molecule wraps around ________, forming a bead- like structure.

Maintenance

________: new cells produced to replace worn out /dead cells.

formation of ova

The ________ and sperm follow the process of meiosis, specializations dependent on their function.

Repair

________: They can regenerate damaged tissues (finger cut → new skin)

Interphase

________: growth stage consists of G1, S & G2.

Chromatin

________ Strands: The bead- like structure is packed tightly, producing ________ strands.

Genetic differences

________ rarely occur, but are the result of a mutation.

Sperm

________ are designed for movement (little cytoplasm), lots of cell division, produce 4 small sperm.

Chromatin Fibres

________: Stands from loops which are attached to a supporting protein scaffold.

Meiosis II

________ is completed if /when the oocyte is fertilized.

Spindle

________ fibres attach to the centromeres.

Chromosomes

________: Protein scaffold folds further to condense the genetic material into ________ (duplicate during replication)

Chromatids

________ move to opposite poles.

Spindle

________ fibres attach to centromeres.

Growth/Differentiation

Mitosis enables organisms to grow from a single-celled zygote into a mature organism that might contain hundreds of trillions of specialized cells

Maintenance

new cells produced to replace worn out/dead cells

Repair

They can regenerate damaged tissues (finger cut → new skin)

DNA Molecule

two sugar-phosphate backbones with nitrogen base "rungs"

Histones

DNA molecule wraps around histones, forming a bead-like structure

Chromatin Strands

The bead-like structure is packed tightly, producing chromatin strands

Chromatin Fibres

Stands from loops which are attached to a supporting protein scaffold

Chromosomes

Protein scaffold folds further to condense the genetic material into chromosomes (duplicate during replication)

Interphase

growth stage consists of G1, S & G2

G1 (first cell growth stage)

organelle replication

S (synthesis phase)

DNA is replicated

G2 (second cell growth stage)

rebuilds energy reserves and prepares for mitosis

Cell Division (Mitosis)

division of genetic material & nucleus

Meiosis I

separates homologous chromosomes (first division)

Meiosis II

separates sister chromatids (second division)

Note

Meiosis II is very similar to Mitosis

Eggs are designed to nourish the zygote

only one ovum is produced per oocyte → the other 3 polar bodies sacrifice their cytoplasm to produce one large egg