Chapter 11 Germ cells, fertilization and sex The development of germ cells Gametes: eggs and sperm Determination of the sexual phenotype Sex chromosomes

Divide less often Meiosis Primordial germ cell -special cytoplasm Germ plasm-polar granules, pole plasm Irradiated with UV light (RNA and proteins) Induce specification Specified Migration into the gonads Germ cell formation Fig. 11-1, transplanted pole plasm

Figure 16.5 Localization of germ cell-less gene products in the posterior of the Drosophila egg and embryo

Oskar—organization and assembly of the pole plasm mRNA-posterior pole—3’ untranslated region Germ plasm specification Fig. 11-4, oskar alone is sufficient to initiate the specification of germ cells

large germ cells are surrounded by smaller somatic cells, then the anterior somatic cells separate into 16 clusters about 10 disc-shaped cells (form the terminal filaments) Formation of germarium Large eggs: arrest--double the diploid number of genes Insect—amplification of genes, yolk protein—liver, fat bodies Nurse cells

Figure 16.4 Formation of 16 interconnected cystocytes in Drosophila

Figure 16.4 Formation of 16 interconnected cystocytes in Drosophila (Part 1)

Figure 16.4 Formation of 16 interconnected cystocytes in Drosophila (Part 2)

Asymmetrical distribution of P granules in germline cells Fig PGL-1—mRNA metabolism PIE-1: repress transcription

Figure 16.2 Inhibition of transcription in germ cell precursors of Caenorhabditis elegans

Germ-cell formation in the mouse Fig. 11-3, PGCs (Fragilis--TM), stella and Oct-4

Figure 16.8 Expression of Oct4 mRNA correlates with totipotency and ability to form germ cells in mammals

Figure 16.9 Photomicrograph of a section through a mouse teratocarcinoma, showing numerous differentiated cell types

Figure Protocol for breeding mice whose genes are derived largely from tumor cells

Primordial germ cell migration in mouse Fig White spotting: Kit receptor Migrating germ cells Steel: Ligand In the cells along which the germ cell migrate

Figure Primordial germ cell migration in the mouse

Figure Migration of germ cells in the Drosophila embryo Germ cell—extragonadal origin, migrate to reach the somatic gonad

Figure Migration of germ cells in the Drosophila embryo (Part 1)

nanos, pumilio mutants stall at the outer gut surface differentiate prematurely---act as complete migration to the somatic gonads nanos target: RNA binding protein Sex lethal (Sxl)--- splicing and translational regulation

PGC migration----Genes and mechanisms Genetic screen—somatically expressed genes Guidance (cues): Wunen: repulsive signal (exclude migrating pole cells from wrong places) Misexpression wunen: transform a tissue permissive to PGC to repulsive one Phosphatidic acid phosphatase 2 (transmembrane protein) Columbus: factor (gonadal mesoderm) attracts pole cells Misexpression Columbus—attract PGCs to tissues other than gonadal mesoderm 3-hydroxy-3-methylglutaryl coenzymeA reductase (cholesterol biosynthesis in human, Geranyl-geranyl group to Chemoattractant)

Figure Specification and migration of germ cells in zebrafish

Meiosis produces haploid cells Fig without replication

Oogenesis and spermatogenesis in mammals-I Fig. 11-7

Oogenesis and spermatogenesis in mammals-II Fig Sexually mature at puberty complete Sexually mature

Figure Regulation of the mitosis/meiosis decision in the adult germline of C. elegans (Part 1)

Figure Regulation of the mitosis/meiosis decision in the adult germline of C. elegans (Part 2)

Figure Regulation of the mitosis/meiosis decision in the adult germline of C. elegans (Part 3)

Figure Retinoic acid (RA) determines the timing of meiosis and sexual differentiation of mammalian germ cells (Part 1)

Figure Retinoic acid (RA) determines the timing of meiosis and sexual differentiation of mammalian germ cells (Part 2)

Paternal and maternal genomes Fig. 11-8

Imprinting of genes controlling embryonic growth Fig parental-conflict theory Reversible process, DNA methylation IGF-2: placenta—growth hormone—large offspring