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65 Cards in this Set

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fusion of male and female gametes to form a zygote


is the branch of biology that studies the development of gametes

Major approaches to embrology

anatomical: distinguish parts



Levels of Organization

Cells, tissues, organs, organ system, organism, community, population, ecosystem


DNA replication that is followed by two rounds of cell division to produce four daughter cells; each with half the number of chromosomes as the original parent cell.

(sex cells)

Comparative embrology

Aristotle studying various animal birth methods

Oviparity: from eggs

Viviparity: live birth

Ovoviviparity: egg that hatches inside body

Epigenesis vs. Preformation

Epigenesis: the process by which plants/ animals/fungi develop from a seed through a sequence of steps in which cells differentiate and organs form

Preformation: the adult organism that develops from it, is preformed in the sex cells

Primary Germ Layers

Ectoderm: outer layer (epidermis of skin, CNS melanocyte)

Mesoderm: middle layer (notochord, head, RBC, bone tissue, facial mucsles)

Endoderm: internal layer (stomach cells, thryoid cells, lung cells)

Fate Maps

use cell labeling techniques to trace cell lineages

Labeling Techniques

-individual cells are labeled and followed to see what they become(groups too)

1. host embryo sectioned for microscopy

2. radioactive cells are descendants of the graft and distinguished by auto-radiography

-radioactive, fluorescent, vital dye staining, genetic marking

Evolutionary Embryology

-Charles Darwin noted embryonic resemblances and correlated different animal groups.

-"Community of decent"- origin of species

Embryonic Homologies

homologous: structures that look alike due to common ancestry

analogous: structures that look alike due to similar function

Medical Embryology

using the information known about human embryos to predict genetic abnormalities, birth defects, malformations and mutations.


the study of disruptions or abnormalities caused by extraneous agents (chemicals, viruses, radiation) that disrupt normal development

Chromosomal Sex Determination

Mammals; presence or absence of X or Y

birds; male= ZZ female=ZW

fruit fly; X=male XX=female XXAAA=mosaic

humans; XX= female XY=male

Primary Sex Determination (mammals)

determination of ovaries( female) and testes (male); relates to chromosomes

Secondary Sex Determination

sexual phenotype as well a hormones and paracrine factors





Sex Determination in Drosophila

In Drosophila, sex determination is achieved by a balance of female determinants on the X chromosome and male determinants on the autosomes.



XO:AA=sterile male

Environmental Sex Determination

Alligators; eggs <30C=female & >34C=male

Bonellia Viridis; larva on the sea floor=female & larva on the female's proboscis=male

Phenotypic Plasticity

the ability of an organism to react to environmental factors by changing form, state of activity or movement.

Norm of Reaction

a genome encoding for a continuous range of possible phenotypes


different phenotypes produced by the environmental conditions


discontinuous phenotypes elicited by the environment

Diet and DNA Induced Methylation

changes that occur in phenotypes

-a diet rich in methyl donors (5-methyl-cytosine) resulted in health mice with black fur

-with out methylation the mice were yellow and fat

Life Cycle of Slime Mold

spore, germinating spore, amoeboid cell (flagellated), feeding plasmodium, fruiting body, spoorangium

Developmental Symbiosis

Parasitism: 1 partner benefits

Mutualism: both partners benefit

Commensalism: 1 partner benefits the other neutral

Regulation of Gene Expression

Differential: regulates nuclear gene transcription into RNA

Selective Nuclear RNA Processing: determines which of the transcribed RNA will enter cytoplasm>mRNA

Selective mRNA Translation: regulate translation of genetic info>mRNA>proteins

Differential Protein Modification: determine which proteins remain and function in the cell

Evidence for Genomic Equivalence

polytene chromosomes; DNA replication w/out separation

-frog blastula cell nuclei directed the complete development of somatic cells>tadpoles


the process of producing similar populations of genetically identical individuals via somatic nuclear transfer that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually.

Polymerase Chain Reaction

Denaturation: seperation of DNA strands(>90C)

Annealing: slow cooling for primer hybrid.

Extension: repeating step1&2 w/ thermal stable enzyme (Taq)

Dolly the Sheep

egg and cell fused with electric current>embryo cultured for 7 days>embryo transferred to surrogate mother>Dolly

Differential Gene Transcription

This H1-dependent conformation of nucleosomes inhibits the transcription of genes in somatic cells by packing adjacent nucleosomes together into tight arrays that prohibit the access of transcription factors and RNA polymerases to the genes

Anatomy of the gene

Introns and Exons

Promoter Region

transcription start site that contains sequences that are bound by RNA polymerase

Transcription Iniation

binding of RNA polymerase to double-stranded DNA; this step involves a transition to single-strandedness in the region of binding; RNA polymerase binds at a sequence of DNA called the promoter.Transcription

Translation Initiation

mRNA+initiator tRNA+ribosomal subunits= complex to start translation


located near the transcription start sites of genes, on the same strand and upstream on the DNA (towards the 5' regionof the sense strand)

-start transcription

-sequence called TATA Box(flanked by CpG islands)


a DNA sequence that controls the efficiency and rate of transcription of a specific promoter

Transcription Factors

proteins that bind to enhancers or promoter regions and interact to activate or repress transcription of a particular gene

Transcription Factor Domains

DNA Binding Domain: ID and binds a particular DNA sequence

Trans-activating Domain: activates or suppresses the transcription of the gene its bound to

Protein Protein Interaction Domain: allows transcription factor activity to be modulated by proteins and other transcription factors

DNA Methylation

promoters of inactive genes become methylated at some cytosine residues and thus stabilizes nucleosomes, preventing transcription factors from binding DNA

-can only methylate if they are flanked by CpG islands

-transcription regulation method

Consequences of DNA Methylation

Genomic Imprinting: genes being active in early embryo; coming from egg or sperm

X-Inactivation: doubling the rate of transcription in the single male X-chromosome>makes the same# of transcripts as female(dosage compensation)>inactivation of one X-chromosome(for females)

RNA Processing

To become an active protein, the RNA must be (1) processed into a messenger RNA by the removal of introns, (2) translocated from the nucleus to the cytoplasm, and (3) translated by the protein-synthesizing apparatus. In some cases, the synthesized protein is not in its mature form and (4) must be posttranslationally modified to become active.

-longer life of mRNA> more proteins translated from it

depends on length of poly A tail on 3' end

Cell Adhesion

cells interact and attach to a surface, substrate or anothercell, mediated by interactions between molecules of the cell surface.


Type-1 transmembrane proteins that play important roles in cell adhesion, forming adherens junctions to bind cells within tissues together.

-They are dependent on calcium (Ca2+) ions to function, hence their name.


interaction at close range between 2+ cells/tissues of different histories and properties


ability to respond to a specific signal

Induction Cascade

loigand initiation to extracellular domain>conformation change in receptors structure>cytoplasmic change>enzymatic activity (kinase)>phosphorylation>activation of transcription factor or cytoskelatal protein

Paracrine Factors

When proteins synthesized by one cell can diffuse over small distances to induce changes in neighboring cells

Juxtacrine Interactions

cell membrane proteins on one cell surface interact with receptor proteins on adjacent cell surfaces

Endocrine Factors

hormones travel through the blood to exert their effects

Autocrine Regulation

the same cells that secrete paracrine factors also respond to them

Cell Death Pathways

In Mammals


In Nematodes


Extracellular Matrix as Source of Developmental Signals

has macromolucules secreted by cells into immediate envrionment that form a region of non-cellular material spaces between cells>attachment sites for cells>permissive substrate for cell adhesion, migration and formation of epithelial sheets


receptors for extracellular matrix molecules; integrate extracellular and intracellular proteins for team work

Structure of Gametes

Germ to Sperm

Recognition of Sperm and Egg

Chemoattractioin: egg secretes soluble molecules for the sperm

Exocytosis: acrosomal vesicle releases enzymes

Binding: sperm attaches to vitelline(extracellular matrix) of egg

Passage: sperm passes through vitelline

Fusion of egg and sperm

Sea Urchin Fertilization

the eggs shed or secrete small peptides such as resact that act as chemotactic factors for the sperm>the sperm sense the pH gradient (and peptide)and move toward it>sperm come in contact with egg jelly>acrosome reaction>fusion

Acrosome reaction

fusion of the acrosomal vesicle with the sperm cell membrane and extansion of the acrosomal process

Fusion of Egg and Sperm Membrane

protein mediated: polymerization of actin molecules>fertilization cone >actin from sperm and egg from bridge for nucleus

bindin found in the sperm

Prevention of Polyspermy

Fast Block: cytoplasm of oocyte has <Na and K+ is inside, the resting membrane potential increases when binding occurs> the influx has to be +20 (fusion happens when the resting membrane potential is stable) 1-3 sec

Slow Block: removel of sperm bound to vitilline membrane by cortical granule rxn cause by increase in Ca2+ 1 min

Cell Commitmet

Labile Specification: differentiate autonomously in neutral environment(reversible)

Determined: diifferentiate in another region of embryo (irreversible)

Modes of Cell Commitment

Autonomous: mosaic embryogenesis (develop on its on depending on origin)

Conditional: cell specific condition (neighboring cells)

Syncytial: different parts of the same cell