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
Paracrine Developmental Mediators
Extracellular Growth Factors
Fibroblast growth factor (FGF) Family
Hedgehog Family
Transcription Factors mediating development
Regulate gene expression and differentiation
HOX, PAX, and T-BOX Families
Sonic Hedgehog (Shh)
Transcription regulating protein with axis specification
Shh binds to patched, removes smothened inhibition
Activates GLI Transcription factors
Homeobox (HOX) Genes
Conserved transcription factors that regulate body segmentation
Differential combinations create segments
Pattern formationi
Axis specification-
Dorsal/ventral
Anterior/posterior
Right/left
Limb formation
Mesoderm cells divide and protrude forming limb bud
Apical Ectodermal Ridge (AER) cells on end regulate proximal/distal growth
Zone of Polarizing Activity (ZPA) found under AER releases Shh to regulate anterior-posterior development
Congenital Abnormalities
Birth defects in structure or function from intrauterine life
Dysmorphology
Study of congenital birth defects that alter form of newborn
Determine maternal health, environmental, and genetic contributions
Syndromic Abnormality Pattern
Causative agent causes defects in parallel
Brachio-oto-renal dysplasia
Error in conserved ear and kidney genes causes ear, neck, and kidney abnormalities
Sequential Abnormality Pattern
Defects in single organ cause further symptoms
Robin Sequence
U-shaped cleft palate and small mandible
Mandibular restriction cause posterior tongue alignment, disrupts palate shelves, creates cleft palate
Malformations
Intrinsic error in embryonic tissue formation
Genetic, maternal diabetes or medication, or infection as potential causes
Deformation
Abnormal form or position of body region
Caused by extrinsic factors impinging on fetal development thru 35-38 weeks
Malformed uterus, crowding, or decreases in amniotic fluid
Disruptions
Extrinsic factors destroy fetal tissue
Vascular insufficiency, trauma, or teratogens
Teratogens
Chemical or other agents that cause birth defects
Thalidomide, cocaine, cigarettes, alcohol, viruses, nutrient excess
Factors influencing teratogenicity
Timing, dosage, and duration
Ability to cross placenta
Maternal and fetal genetic susceptibility
Mechanism of action
Hirschsprung Disease (HSCR)
Congenital megacolon caused by neural crest failure to innervate internal anal sphincter
Bowel becomes dilated via obstruction
Mortality due to ruptured colon
Gorlin Syndrome
Mutation in patch 1 in Shh pathway
Patch 1 acts as tumor suppressant
Increased risk of cancer and de novo mutations
Hutchinson-Fuilford Progeria Syndrome (Progeria)
Disorder of accelerated aging
Mutations in LMNA Gene- Encodes lamin A
Abnormal Lamin A- Progerin- Unstable nuclear envelope
Increased DNA damage- Growth failure
Baldness, cranial defects
Loss of body fat, dry scaly skin, stiff joints
Cardiovascular issues and insulin resistance
Traits associated with longevity
Insulin resistance
Control of cell cycle
Lipid metabolism
Immune and stress responses
Antioxidant enzyme expression
Nutrient metabolism
