BSC2011 Final Exam Study Guide Unit I Review DNA The Central Dogma the flow of genetic information is basic to all living things o Three entities DNA mRNA Protein o Three processes Replication transcription translation o Genetic information is stored in the order of sequence of nucleotides o Gene a discrete unit of hereditary information on part of a chromosome o Genome refers to all of an organisms genetic material in a cell o 1 chromosome 1 long double stranded helical DNA molecule and its bound Chromosomes proteins Composed of chromatins Eukaryotic chromosomes require DNA packing Euchromatin loosely packed actively transcribed DNA proteins Heterochromatin tightly packed genetically inactive DNA proteins RNA an intermediary molecule in the flow of genetic information o Three major types of RNA mRNA tRNA and rRNA Transcription gene expression the synthesis of mRNA using DNA as a template o Steps Elongation RNA polymerase moves along DNA template and joins RNA Initiation RNA polymerase binds to promoter sequence Termination the pre mRNA transcript disengages from the RNA nucleotides polymerase o Processing Capping and tailing Splicing introns spliced out exons get expressed Translation process by which transcribed mRNA in the nucleus is decoded into a specific protein at a ribosome in the cytoplasm o The genetic code a codon codes for one amino acid The code is redundant due to 3rd base wobble The code is virtually universal o The process Spliced mRNA binds to a ribosome in the cytoplasm The correct tRNA molecule binds to mRNA Mutation a change in the genetic material of a cell o Nucleotide substitution may or may not change the amino acid functional protein Silent mutation no change Missense mutation change occurs o Nucleotide indel causes a frameshift mutation by altering the codon reading frame May result in a nonsense mutation an early or no stop signal no protein The critical role of proteins in cells organisms o Types and functions Enzymes Structural Transport Hormones Receptors Defense Storage Cell signaling and communication o Cells use signaling mechanisms to regulate cell activities and community with other cells o Three stages of cell signaling Reception transduction response Gene regulation in Eukaryotes o Gene regulation the control of gene expression o Some genes have constitutive expression always on o Other genes can either be expressed or repressed facultative expression o There are various levels of control of gene expression in Eukaryotes o Control at transcription level Signal molecules will target protein receptors on in cells and control gene expression Unit I cont Animal Development Cellular processes guiding embryonic development o For a zygote fertilized egg cell to develop into a multicellular embryo requires Cell division cell differentiation morphogenesis Processes guiding embryonic cell differentiation o Genomic equivalence all the different cells types in an organism have identical genomes but they express different genes o Totipotency the potential of a cell to differentiate into an entire organism because no genes are irreversibly turned off Evidence for totipotency Nuclear transplantation reproductive cloning Stem cells relatively undifferentiated cells that can be induced to differentiate Embryonic stem cells o Can be totipotent pluripotent differentiate into any cell type and multipotent differentiate into some cell types Molecular processes underlying embryonic cell differentiation o Determination a process by which a cell differentiates into a particular cell type by expressing a unique set of genes o Cytoplasmic determinants CDs act as signal molecules that can help regulate gene expression o Cells can also differentiate later in development via induction of cells Fertilization Sea Urchin development o Acrosome located in the head of sperm membrane bound vesicle containing hydrolytic enzymes for egg penetration o The fertilization process Contact sperm s acrosome releases hydrolytic enzymes to digest egg s outer jelly coat Acrosomal reaction sperm ejects an acrosomal process protein receptors in egg cell membrane recognize and bind to acrosomal process proteins Egg and sperm cell membranes fuse egg cell membrane becomes depolarized resulted in a fast block to polyspermy temporary Cortical reaction Wave of calcium ions from ER at sperm site stimulates release of cortical enzymes from cortical granules fertilization envelope forms slow block to polyspermy permanent Nulcei fuse a zygote is created with a full set of chromosomes Cleavage Sea Urchin development cont o A rapid series of mitotic cell divisions that occurs in the absence of cell growth o Morula solid ball of cells o Blastula hollow ball of cells Blastocoel the hollow cavity Blastomere each cell in blastula o For a chick egg cleavage is at cytoplasmic disk only contains embryonic cell mass called the blastoderm with an upper epiblast and lower hypoblast o Cleavage Summary Sea Urchin microlecithal holoblastic cleavage Frog mesolecithal holoblastic cleavage Chicken macrolecithal meroblastic cleavage Gastrulation morphogenesis Sea Urchin development cont o An undifferentiated mass of embryonic cells begins to take shape A series of cell movements rearrange the position of cells in the embryo o Results in an early embryo gastrula that has three primary germ layers Outer ectoderm Skin epidermis central and peripheral nervous system Pituitary gland subcutaneous glands mammary glands Hair nails teeth Most facial and ear bones Middle mesoderm Skeletal system spine ribs limb bones Cartilage connective tissue Circulatory system heart and blood vessels spleen Reproductive system ovaries testes Excretory system kidneys Muscles notochord Inner endoderm Thyroid thymus pancreas liver tonsils Lining of bladder and digestive and respiratory tracts o Also creates a primitive gut called the archenteron o Ingression inner mesenchyme cells undergo ingression migration at the onset of gastrulation archenteron o Invagination outer cells at the vegetal pole invaginate to produce the o Involution in frogs outer animal pole cells spread over surface and inward o Primitive streak in chickens equivalent of a blastopore Neurulation of surface ectodermal cells is induced by the underlying notochord Neural plate forms Neural folds and neural groove form Changes in cell shape cause uplifting of cells Neutral tube forms once the neural folds meet A change in cell adhesion pinches off neural tube from underlying and
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