Cell Division

Cell Division

Continuity of life, Multicellular, Development, Growth, Repair

DNA STRUCTURE

Defines the basic genetic makeup of our body

DNA

Constitutes the cell’s genome (consist of a single DNA molecule or a number of DNA molecules)

Somatic cells (nonreproductive cells)

have two sets of chromosomes

Gametes (reproductive cells: sperm and egg)

have half as many chromosomes as somatic cells (n)

Eukaryotic chromosomes

consist of chromatin a complex of DNA and protein

G1

period of cellular growth/organelles are duplicated

S

DNA synthesis/ DNA replicated

G2

checkpoint: checks for errors in the DNA

G0

cell cycle arrest (cells just do the function)

Prophase

Chromosomes are visible, Nucleolus disappears, Centrosomes make their way to polar reasons, Nuclear starts to dissolve, Formation of spindle

Prometaphase

Nuclear membrane has dissolved, Centrosomes arrived at polar regions, Spindles attach to the kinetochore

Metaphase

Chromosomes align at the metaphase pate (equatorial region), Checkpoint 2

Anaphase

Sister chromatids are pulled apart and towards the polar regions

Telophase

Chromosomes unravel to become chromatin, Nucleoli reappear, Nuclear membrane starts to form, Spindles disappe

ar

Late Telophase

Cleavage furrow is more prominent

Cytokinesis

Clearing of the cytoplasm giving rise to 2 daughter cells

Meiosis

Reduces from diploid to haploid, Preceded by replication of chromosomes, Takes place in two sets of cell division (Meiosis I and Meiosis II), Sister chromatids are generally identical and joined at the centromere

Fertilization

Union of gametes, Fertilized egg is called zygote

Leptotene

condensation of chromosomes

Zygotene

synopsis between homologous chromosomes, Formation of synaptonemal complex, Formation of bipotent

Pachytene

crossing over

Diplotene

dissolution of synaptonemal

Diakinesis

dissolution of nuclear membrane

Prophase II

same with mitosis

Metaphase I

homologous pairs line up in the equator

Anaphase I

homologous chromosomes separate

Anaphase II

sister chromatids separate

Telophase I and Cytokinesis

same as mitosis but the DNA material is not deployed

Telophase II and Cytokinesis

Haploid daughter cells forming, Not genetically the

Mutations

• Change in DNA sequence

DNA copying mistake, Ionizing radiation, Mutagens

Chromosol Mutation

unpredictable change that occurs in chromosomes

Deletions

Breakage of a chromosome (becomes lost), Genetic disorders (male infertility)

Cystic Fibrosis

Stops production of protein in lung cells & pancreas, Thick mucus, bacterial infections in lung,

Translocation

Fragments of a chromosome joins a non-homologous chromosome, Disorders (infertility and cancer)

Duplication

extra copies of genes on a chromosome

MECP2

severe intellectual inability

Inversion

segments of (c.) breaks off, flips, and reattaches

Hemophilia

inherited bleeding disorder (blood does not clot properly)

Aneuploidy

unnatural number of chromosomes

Nondisjunction

c.p. fails to separate properly during meiosis

Monosomy

Gamete has 1 less chromosome, 45 chromosomes are the result

Turner Syndrome

missing a sex chromosome (female)

Trisomy

Gamete has 1 more chromosome, 47 chromosomes

Downs Syndrome

extra #21 chromosomes

Klinefelter Syndrome

male has extra x chromosome

Genetics

scientific study of heredity and variation

Heredity

transmission traits from one generation to the other

Variation

demonstrated by the differences in appearances from offspring to parents

Genes

units of heredity and are segments of DNA

Gametes

reproductive cells with genes

Locus

specific location of a gene

Chrimosomes

Sister chromatids are pulled apart and towards the polar regions

Karyotype

ordered display of the chromosome pairs