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110 Cards in this Set
- Front
- Back
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Sea Urchin
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-Strongylocentrotus purpuratus
-external fertilization -large numbers of eggs, sperm and embryos -transparent and transluscent |
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Xenopus laevis
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-African clawed frog
-external fertilization -large, transluscent eggs -sensitive to environmental toxins |
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Caenorhabditis elegans
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-nematode, usually called C. elegans
-small animal with short life cycle -cheap and easy to keep large numbers -first multicellular organism whose genome was completely sequenced -can manipulate genes with RNAi |
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Drosophila Melanogaster
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-fruit fly
-small animal with short life cycle -mutant flies, with defects in any of several thousand genes are available -entire genome recently sequenced -can manipulate genes with p-elements |
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Mouse
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-Mus musculus =classic model vertebrate
-many inbred strains exist, as well as lines selected for particular traits -short life cycle with large, offspring numbers -viviparour development |
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Zebrafish
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-small fish is a relatively new model
-vertebrate model for aspects of human biology -cheaper and easier to handle than mice -transparent and readily accessible embryo (oviparous) |
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Determination
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-commitment of cells to a particular fate
-e.g. round worm (Caenorhabhitis elegans) |
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Morphogenesis
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-gives rise to shape of the multicellular body
-development of adult form -involves movement of cells and tissues. |
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Differentiation
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-development of cellular specificity
-e.g. tissue-specific patterns of gene expression |
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Blastula
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hollow balls of cells
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Gastrula
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region of blastula that folds inward, forming a gut cavity
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The gray crescent
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unequal distribution of cytoplasm in frogs
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Vegetal hemisphere
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bottom of unfertilized frog eggs, where dense nutrients settle
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animal hemisphere
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opposite end of egg, where haploid nucleus is located
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Animal pole
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-location where sperm always enters the egg
-causes rotation of cytoplasm and initiation of bilateral symmetry |
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Spemann's experiment
(1900s) |
-baby hair used to constrict zygote
-if hair bisects gray crescent, development is normal in both derivative embryos -if not, blastomere without grey crescent develops abnormally -cytoplasmic factors drive early development |
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Cleavage
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-rapid series of cell divisions which differentially distribute nutrients and information molecules such as mRNA
-DNA synthesis and cell divisions proceed with little growth and gene expression, so cleavage produces blastula |
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Factors influencing cleavage patterns
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-amount of yolk
-orientation of mitotic spindles e.g. radial and spiral |
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Mitotic spindles: radial
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right angles
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mitotic spindles: spiral
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not at right angles
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Complete cleavage
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-sea urchins have yolk platelets evenly distributed
-frogs have yolks concentrated at vegetal poles |
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Incomplete cleavage
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chicks have embryos develop on top of yolks as disk of cells
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superficial cleavage
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-Drosophilas have multiple nuclear divisions with cytokinesis
-they produce syncytium -nuclei migrate to periphery and plasma membranes form |
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Gastrulation
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dramatic rearrangement of cells of a blastula into a three-layered embryo which has a primitive gut
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Lewis Wolpert on gastrulation
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It is not birth, marriage, or death, but gastrulation which is the truly important event in your life
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Ectoderm
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germ layer which forms outer or epidermal layer
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mesoderm
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germ layer which forms muscle, bone, blood, and connective tissue
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endoderm
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germ layer which form lining of the gut, liver, and lungs
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maternal effect genes
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bicoid mRNA in egg
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Gap genes
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basic anterior/ posterior subdivisions; mutants have gaps in segmentation
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pair-rule genes
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mutants have 1/2 normal segment number
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homeotic genes
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set of genes expressed in different combinations along length of body (anterior/posterior axis) that dictate fate of each segment
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homeotic mutants
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mutants in which normal body parts are formed in inappropriate segments
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Biothorax mutant
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Transforms 3rd thoracic segment, which normally bears haltares, into form of 2nd thoracic segment, which bears wings
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Antennapedia mutation
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Causes flies to grow legs in place of antennae
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Hox genes
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-Class of homeotic genes extensively studied in nematodes, insects, and mice
-Contains homeobox sequence that codes for a homeodomain protein -exhibit spatial colinearity -exhibit temporal colinearity in vertebrates |
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Homeodomain Protein
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Binds to DNA and acts as a transcription factor
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Spatial colinearity
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Arranged in same order on each chromosome as they are expressed along the anterior to posterior axis in the developing animal
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Temporal colinearity
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Anterior genes are expressed earlier than posterior genes
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Genomic Imprinting
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-Process by which an allele is silenced or expressed in individual, depending on whether allele transmitted through a sperm or an egg
-Some genes are only expressed from allele inherited from mother, while others solely expressed from allele inherited from father -Arguably most significant discovery in developmental genetics of 20th century -also called parent-of-origin gene expression -epigenetic form of gene expression -known to be about 80 imprinted loci in humans |
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Epigenetics
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-heritable changes in gene function that occur without a change in DNA sequence
-alleles methylated differently during male and female gametogenetics |
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Viviparity intensifies genetic conflict
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-Nourishment of embryo by mother creates post-fertilization arena for genomic conflict absent in species that lay eggs
-provides direct conduit for manipulation of mother's physiological system by paternal genes in embryos |
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Conflict over maternal resources can arise between
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-mother and developing embryos
-sibling embryos within womb -maternal and paternal genomes within individual embryos |
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Viviparity provides...
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direct conduit for manipulation of mother's physiological system by paternal genes in embryo
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The placenta...
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-is an interface between maternal and fetal tissues
-acquires nutrients from mother -transports hormones from fetus that influences maternal physiology -highly invasive organ |
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The placenta develops from..
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embryonic trophoblast cells that invade endometrium and remodel maternal spiral arteries into distended vessels that are unable to constrict
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Paternal genes control...
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growth of placents
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maternal-fetal interactions involve...
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complex interplay between mutual and conflicting interests
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Genomic imprinting in understanding pregnancy
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epigenetic machinery of DNA methylation provides molecular mechanism through which conflict between mother and paternal genome in fetus can be played out
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Genomic imprinting in mammalian development
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-opposing contributions of maternal and paternal genomes demonstrated by nuclear transplantation experiments on mice
-created diploid embryos with either 2 paternal or 2 maternal genomes |
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Androgenic embryos
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had form-without-growth development of fetus and overgrowth of placenta
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Gynogenic embryos
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had form-without-growth development of fetus and gross underdevelopment of placenta
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Hydatidiform moles
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-same patterns of aberrant development occur naturally in fetuses with maternal/paternal chromosome imbalances
-complete mole contains no fetal tissue -extensive overgrowth of trophoblast and chorionic villi develop into a grape-like cluster that can fill the uterus |
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lgf2 codes for...
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IGF-II: insulin -related polypeptide growth factor
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lgf2r
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-aka. mannose 6-phosphate receptor
-involved in transporting enzymes to lysosomes for destruction |
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lgf2 expression
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-paternal allele expressed
-maternal allele silent |
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lgf2r expression
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-paternal allele silent
-maternal allele expressed |
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Paternal lgf2 allele promotes...
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resource transfer from maternal tissue to embryo
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Maternal lgf2r allele...
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limits that transfer
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Genomic imprinting is known to occur in...
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-angiosperms, marsupials, and eutherian mammals
-all organisms with "placental habit" |
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In flowering plants and animals, developing offspring are nourished..
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directly from maternal tissues
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Thus, genes expressed in embryo or seed can...
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influence quantity of resources that offspring receives from mother
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By contrast, in oviparous taxa,...
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amount of yolk is usually determined before or immediately after fertilization
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Thus, in oviparous taxa, genes expressed in embryo cannot...
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exert influence on amount of resources transferred from mother
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The conflict hypothesis for imprinting
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• Female mammals typically mate with more than one male and produce multiple-paternity offspring
• Selection acting on mother favors equal allocation of her resources across all offspring • By contrast, any individual offspring is selected to bias nutrient transfer to itself • This selfish behavior is moderated in maternally inherited alleles because they are related to mother and to both full and half siblings • By contrast, paternally-inherited alleles are related neither to mother nor to half siblings • Selection therefore favors aggressive paternal alleles that maximize nutrient transfer from mother to embryo and maternal alleles that hold this selfish paternal gene expression in check |
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Evolution of genomic imprinting...
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-is driven by tug-of-war conflict between maternally- and paternally-inherited alleles in embryo over
amount of nutrients that embryo draws from mother -the coevolutionary process of adaptation and counter-adaptation maintains a balance between opposing sides that obscures the conflict itself -conflict becomes apparent when balance is disrupted |
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Concepti with abnormal complement of maternal and paternal chromosomes
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-hydatidiform moles
-invasive trophoblast disease |
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Maternal versus paternal chromosomes deletions (genetic cause)
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-Angelman Syndrome: deletion of maternally-inherited segment of 15q
– Prader-Willi Syndrome: deletion of paternally-inherited segment of 15q |
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Maternal versus paternal disruption of imprinted gene expression (epigenetic
cause) |
– Beckwith-Wiedemann Syndrome: abnormal expression of maternally-inherited
gene – Silver-Russell Syndrome: abnormal expression of paternally-inherited gene |
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Imprinting disruption and neurological/behavioral disorders
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– Turner Syndrome: differing behavioral and cognitive phenotypes of XPO and XMO
females |
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Imprinting disruption and cancer
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– Proto-oncogenes:
maternally-expressed genes – Tumor suppressor genes: maternally-expressed genes |
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Tigon versus Liger
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• Relative to parental species, tigons are small, weighing ~ 350 lbs
• Ligers are huge, weighing over 1,100 lbs (twice that of adult male lion) and reaching 12 ft in length • Potential for multiple paternity much greater in lions than in tigers • Consequently, selection favors more aggressive paternal genomes and more defensive maternal genomes in lions than in tigers • Uncoupling of maternal and paternal genomes produces asymmetrical growth in reciprocal hybrids |
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Hormone
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chemical signal secreted into body fluids (usu. blood) which communicates regulatory messages
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Endocrine Glands
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Hormone secreting organs
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Endocrinology
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the study of hormones and the endocrine system
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Endocrine system
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all of an animal's hormone secreting cells
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Nervous and endocrine systems
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the two systems of internal communication and regulation
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Neurons
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specialized cells through which nervous system conveys high-speed electrical signals
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Endocrine systems secrete...
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hormones that coordinate slower but longer-acting responses
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Endocrine and nervous systems function together in maintaining...
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homeostasis, development, and reproduction
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Neurosecretory cells
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specialized nerve cells that release neurohormones into blood
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Both endocrine hormones and neurohormones function as...
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long-distance regulators of physiological processes
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Endocrine Pathway
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– receptor in endocrine gland
responds to stimulus, e.g., lowblood sugar – hormone produced by endocrine gland (e.g., pancreas) is released into bloodstream – hormone binds to receptor on target cell to alter its functioning |
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Neurohormone Pathway
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– receptor in neurosecretory
tissue (hypothalamus/posterior pituitary) responds to stimulus, e.g., suckling – hormone produced by neurosecretory tissue is released into bloodstream – hormone binds to receptor on target cell (e.g., smooth muscle in breast) to alter its functioning |
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Neuroendocrine Pathway
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– receptor in hypothalamus
responds to stimulus – hypothalamus secretes releasing hormone into bloodstream – anterior pituitary responds by releasing hormone (e.g., FSH) into bloodstream – hormone binds to receptor on target cell (seminiferous tubules in testis) to alter its functioning |
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Peptides and proteins
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– peptides such as ADH (9 AA), insulin (51 AA) and growth hormone
(191 AA) – glycoproteins such as luteinizing hormone include two peptide chains with attached carbohydrates |
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Amino Acid Derivatives (amines)
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– tyrosine derivatives such as epinephrine, norepinephrine and thyroid hormones
– tryptophan derivative melatonin |
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Steroids
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– sex steroids such as testosterone and estrogen
– corticosteroids produced by adrenal cortex |
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How do hydrophilic hormones?
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-by proteins, peptides, and amine hormones
• Water soluble or hydrophilic • Don’t enter cells but bind to specific receptor on cell membrane • Initiate multi-step, signal transduction pathway |
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Same hormone may have different effects on target cells with...
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• different receptors for the hormone
• different signal transduction pathways • different proteins for carrying out the response |
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How do steroid hormones work?
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• Lipid soluble or lipophilic • Pass through cell membrane
• Binds with receptor protein • Hormone-protein complex passes through nuclear membrane and binds to specific regulatory site • Stimulates transcription of a specific gene |
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East German athletes in the '70s and '80's: MEN
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– shrunken testicles
– sterility – heart and kidney damage |
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East German athletes in the '70s and '80s: WOMEN
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– increased body hair
– severe acne – increased libido – ovarian cysts – uterine shrinkage |
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Hypothalmus
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– control center that integrates many functions of vertebrate endocrine system
– receives nerve input from throughout body and other parts of brain – produces releasing and inhibiting hormones that control anterior pituitary |
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Pineal Gland
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– secretes melatonin
– contains light-sensitive cells and modulates biorhythms associated with reproduction -Modulates daily rhythm and circadian systems -deals with jet lag |
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Posterior Pituitary Gland
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-aka. NEUROHYPOPHYSIS
-Storage site for hormones produced by hypothalamus -Produces ADH, Oxytocin, and Mesoprosin |
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ADH
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antidiuretic hormone that regulates the amount of water in urine, saves water, etc.
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Oxytocin
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hormone that:
-modulator of behavior during stress -stimulates contraction of uterus and mammary gland cells during childbirth -released during sexual climax in men and women and is involved in dopamine reward system -memory gland during suckling |
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Mesopresin
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another hormone releases
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Oxytocin and stress in women
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• Tend and befriend
• Estrogen facilitates “feel good” effects of oxytocin by moderating release of adrenaline and other stress hormones • Promotes social networking |
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Oxytocin and stress in men
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• Fight or flight
• Testosterone mitigates stress relieving effects of oxytocin -97% of mammals-males leave after sex and leaves the woman to lend to offspring eg. Vole: prairy and montagne species; when you inject them with oxytocin, they act like other 3%; when you don't inject with oxytocin, they act like other 97% of mammals |
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Anterior pituitary gland
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-aka ADENOHYPOPHYSIS
• secretes releasing and inhibitory hormones that control the release of a large number of anterior pituitary hormones -produces hormones -most important gland;produces many important hormones |
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Growth Hormone (GH)
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• Large polypeptide (191 AA)
• Stimulates cells to take up AA, increasing protein synthesis and muscle and connective tissue growth • Promotes bone elongation: stimulates cell division in cartilaginous epiphyseal growth plates of bone • Primary determinant of stature – overproduction of GH results in gigantism –underproduction of GH results in dwarfism • Because skeletal growth plates transform to bone, GH doesn’t increase height in adults eg. Robert Wadlow developed a growth hormone secreting pituitary tumor as a young child and never stopped growing until he died at 22; grew at 4 inches a year; was 8'11", 480 lbs., when he died; died b/c of blister infection he didnt know he had |
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Thyroid Gland secretes...
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secretes:
• Thyroid hormones – Amines – Stimulate & maintain metabolism – Regulated by TSH • Calcitonin – Peptide – Lowers blood calcium and inhibits loss of calcium from bone – Regulated by blood calcium levels (negative feedback) |
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Parathyroid Gland secretes...
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• Parathyroid hormone (PTH)
– Peptide – Raises blood calcium by stimulating bone breakdown – Regulated by blood calcium |
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Adrenal Glands include...
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Medulla:
• Short-term stress response regulated by sympathetic nervous system • Produces catecholamines made from AA tyrosine • Epinephrine (adrenalin) and norepinephrine – raise blood glucose levels – increase basal metabolic rate – constrict blood vessels |
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Adrenal glands also include...
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Cortex:
• Involved in long-term stress response (stimulated by ACTH) • Produces corticosteroids (steroid hormones)that pass through cell membrane; act as transcription factors; and lower immune system function during stress • Effects on lipid and carbohydrate metabolism, immune system function and damage repair |
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Endorphins
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-Hormones of anterior pituitary gland
-endogenous morphine (internally produced) • Peptide hormones discovered in 1970s • In rats, radioactively labeled morphines attached to specific receptors in the rat brain • Heroin and opiate drugs mimic endorphins and bind to same receptors in the brain • Responsible for “runner’s high” and afterglow of eating hot chili peppers -accidentally discovered |
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Natural opiates
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-body naturally produces opiates
-inhibit perception of pain by acting as neurotransmitters in the brain |
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Why do plants produce these compounds?
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Alkaloids--amines produced by plants; opium, morphine, caffeine, and cocaine
-referred to as secondary metabolites/ plant compounds -not required for plant physiology -serve as defensive function for plants by disorienting; inhibiting growth or nervous system of predators |
