Chapter 3- Meiosis Flashcards
Meiosis
Cell division in two stages that produces haploid gametes in germline cells
Maintains chromosome number within species
Meiosis I
Reduction division
Homologous chromosomes separate
Chromosome number reduces from 46 to 23
Crossing over occurs
Meiosis II
Equational division
Sister chromatids separate
Chromosome number remains constant
Mechanisms to Increase Genetic Diversity
Crossing Over
Independent Assortment
Alpha Thalassemia
Misalignment of alpha globin genes can lead to duplication-deletion events
Missing 1+ copies of alpha globin gene leads to globin imbalance and buildup of beta chains
Spermatogenesis
Spermatogonium- Primary Spermatocyte- Secondary Spermatocyte- Sptermatid- Spermatozoa
Continuous division and maturation after puberty
I spermatogonium produces 4 sperm
Oogenesis
Oogonium- Primary oocyte- Secondary oocyte- Ovum
Produce polar bodies during each meiotic division
Begins during utero, Meiosis I finishes during ovulation, Meiosis II completed during fertilization
Stages of Embryonic Development
Fertilization
Cleavage
Gastrulation
Neurulation
Neural Crest Development
Organogenesis
Fertilization
Matured sperm meets oocyte in fallopian tube
Sperm DNA enters oocyte
Meiosis II finishes and induces polarity relative to entry site
Cleavage
Frequent Mitotic divisions to increase cell number
~4 days- 16 cells, morula
Blastocyst- Hollow mass of 100 cells
Trophoblast- Outer layer, becomes chorion and amnio
Inner cell mass becomes embryo
Implantation occurs around day 7
Gastrulation
Invagination and migration to form 3 primary germ layers
Ectoderm- Skin and nervous system
Mesoderm- Muscle
Endoderm- Tracts
Days 14-28
Neurulation
Initiation of organogeneis at weeks 3-4
Ectoderm divides into neural tube and crest
Neural tube folds and pinches off to become CNS
Adjacent neural crest migrate to become pigment and distal neurons and smooth muscle
Organogenesis
Transformation of germ layers into distinct organs
All organs present by week 8- Fetus
Morphogenesis
Process by which order is created in an organism
Mediated by cell growth, migration, interaction and death
Mediated by growth factors and hormones
Processes of morphogenesis
Axis specification, pattern formation, an dorganogenesis