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Cell &Cell Division

AGT Lab Manual Information

Nucleus Membrane, Chromatin, and Nucleoli
Nuclear Matrix Fibrous material that remains if the chromatin and nucleoli are extracted
Heterochromatin Highly condensed chromatin that stains darkly with nuclear stains
Euchromatin More dispersed chromatin which stains lightly or not at all
Diameter of DNA fibers with proteins 30nm
Diameter of protein depleted DNA fibers 10nm
Primary functions of the nucleic acids gene replication (the process of copying sequences of DNA(genes) for distribution to daughter cells) and gene transcription ( the process of copying sequences of DNA into complementary strands of RNA)
Occurrence of protein synthesis cytoplasmic ribosomes
Nuclear envelope porous double membrane surrounding the nucleus with ribosomes attached to the outside; disappears during cell division; contains the nucleolus and the chromatin
Nucleolus 1-4 in the nucleus; site of ribosome precursor assembly; formed by NOR of acrocentric chromosomes; composed of RNA protein, and some DNA
Chromatin composed of DNA, proteins (mainly histones), RNA, and certain polysaccharides
DNA double helix of two strands composed of nucleotides
Nucleotide formation sugar molecule, phosphate groups, and one of four bases: adenine, guanine, thymine, or cytosine
Hydrogen Bonds hold the bases of the two strands together
5-methyl cytosine often concentrated in areas of heterochromatin, such as in 1, 9 , 15, 16, Y
Semiconservative replication two identical copies of the original DNA composed of one original strand and one newly synthesized strand
Codon triplet code of three bases that codes for one amino acid
Gene a linear arrangement of codons giving the instructions for the building of a protein with specific amino acids in a particular order
Missense mutation one that changes a codon specific for one amino acid to one that specifies a different amino acid
Nonsense mutation single base substitution in DNA resulting in a chain termination codon
Introns DNA sequences not present in the mRNA and are not translated into amino acids in that gene's protein
Exons sequences present in the mRNA that usually code for protein
Denaturation to two single-stranded helices High temperature or high-PH will break the hydrogen bonds, unwinding or denaturing the DNA
Hydrogen bonds G-C pairs have three; A-T have two (tend to be more unstable and will denature before G-C)
Tm temperature at which a given DNA will be half denatured or melted; used as an index of the amount of G and C in that DNA
Cot curve curve of the rate at which denature DNA renatures(Co = concentration of single-stranded DNA; t = time); tells how many sequences are present in multiple copies (repetitive DNA) versus how many are unique
Buoyant density of DNA measure of the G-C content by forming gradients of concentration in cesium chloride during centrifugation; depends on DNA strandedness and base composition
RFLPs Restriction fragment length polymorphisms (ex. beta-globin gene on chromosome 11 and HpaI; 7600bps in some; 13,000bps in others [sickle cell disease])
Sickle Cell Disease HpaI restriction enzyme; MstII restriction enzyme: CCTGAGG, 1150 and 200bp; CCTGTGG for affected producing 1350bp
Oligonucleotides (oligo = few) short molecules engineered to match portions of a normal gene exactly; used to detect genetic defects that involve a point mutation or change in a single base
RNA differ from DNA RNA (DNA): 2'-OH group (2'-H group); single-stranded (double-stranded); uracil (thymine) for adenine
Transcription DNA template for complementary strand of RNA
mRNA complementary strand of template DNA; introns are spliced out; molecule moves out of the nucleus to the cytoplasm
tRNA binds the appropriate amino acid to its anticodon (base triplet complementary to a codon in mRNA)
rRNA ribosomal RNA assists in the actual protein synthesis (anticodons of the tRNA molecule bind the codons of the mRNA molecule)
Chromsome proteins histones and nonhistones
Histone protein characterization contained in interphase chromatin; characterized by their basic pH and large numbers of the amino acids arginine and lysine; isoelectric point always more than 10
Nonhistone protein characterization isoelectric point always less than 10; tend to be acidic (4-9); different structural, enzymatic, and regulatory functions
Isoelectric Point pHs at which the average charge of the molecule is zero
Histone protein classes H1 (lysine-rich); H2A&H2B (slightly lysine-rich); H3&H4 (arginine-rich); H5 replaces H1 in nucleated erythrocytes; Histones are extracted from chromatin by dilute acids or by high-molarity salt solutions; ratio to DNA by weight is 1:1
Protamines low molecular weight basic protein that replaces histones in mature sperm
Acetic Acid and Methanol Fixative solution; dissolves out some, if not most, of the histones
Nonhistone proteins include all proteins of chromatin other than histones; more numerous and more variable, but less of the chromatin mass; involved in chromatin metabolism, gene expression, and in higher order structure
Nu-body/Nucleosome octamer of two molecules of each H2A, H2B, H3, & H4 histones (10nm)
H1 histone protein involved in linking and compaction of nucleosomes
Nucleosome basic unit of eukaryotic chromatin, present in dispersed or condensed chromatin, in repetitive areas of unique sequences, and in interphase and metaphase
Heteropyknosis property of chromatin of showing variations in staining intensity owing to differences in the degree of coiling or condensation of the chromatin filaments
Positive Heteropyknosis Chromosomes and segments of chromosomes that are more heavily stained than the rest
Negative Heteropyknosis Chromosomes and segments of chromosomes that are more lightly stained than the rest
Positive Heteropyknosis in G-banding Heterochromatin
Negative Heteropyknosis in G-banding Euchromatin
Facultative heterochromatin condensed, inactive chromatin of X chromosomes in excess of one; may represent one or the other in a given cell; sequences similar to active DNA, does not stain differently, and can become decondensed and active
Constitutive heterochromatin differentially staining areas of chromatin and chromosomes and are constant from cell to cell; rich in repetitive DNA, stains differently from euchromatin; never elongates or decondenses
Heterochromatin Does not code for protein (genetically inactive) and replicate late in the synthesis phase of the cell cycle
Barr body facultative heterochromatin of the second X chromosome - discovery: 1949 Murray L. Barr and Ewart G. Bertram as a "paranucleus"
Russell-Lyon Hypothesis, first part 1. One of the two X chromosomes is inactivated in human females 2. the inactivated X may have either maternal or paternal origin in a given cell of an individual, and the choice is random
Russell-Lyon Hypothesis, last part 3. inactivation occurs in early embryogenesis 4. inactivation is stable, and descendants of a cell with an inactive X inherit that same X in an inactive state
Identifying the inactivated X BrdU for 40-44 hours; add thymidine 6-7 hours before fixation; stain with Hoeschst 33258; observe with fluorescence microscope; or thymidine, then BrdU, and observe pale-staining X
Dosage compensation X inactivation; mechanism for producing equal amounts of gene products in females having two X chromosomes and males having only one
Xq13 inactivation center of the X chromosome
Abnormal X vs Normal X inactivation The abnormal X is usually inactive as they are more likely to survive than when active in cells
X;autosome translocation vs Normal X inactivation The normal X is usually inactive
unbalanced X;autosome trans vs Normal X inactivation the translocation chromosome is usually inactive and may or may not extend into the autosome
5-azacytidine produces hypomethylation of DNA
XIST active only on the inactive X chromosome in band q13
Satellite DNA Repetitive DNA found in constitutive heterochromatin; can mean any highly repeated sequences
Alpha, beta, and classical DNA found at the centromeres of all the chromosomes
SINES Short interspersed elements located in the quinacrine pale bands; containing cleavage sites recognized by the restriction endonuclease AluI
LINES Long interspersed elements located in the quinacrine bright bands; cleavage sites for L1
Microsatellites di- or trinucleotide tandem repeats and are highly polymorphic
SSRs (simple sequence repeats) 3- to 6-bp repeats found in coding and noncoding DNAs and are highly polymorphic
Minisatellites Longer repeats, usually more than 10bp, and usually located at the distal ends of chromosomes, and are highly polymorphic, useful for DNA fingerprinting
Classification of Chromosomal Sequences Beta --> Alpha --> Classical --> Telomeric --> Unique Gene --> Total chromosome
Cell cycle schedule 18 hrs: 9 hr for G1; 5 hr for S; 3 hr for G2; and 1 hr for M
S cycle inhibitors amethopterin (methotrexate); hydroxyurea; and cytosine arabinoside
Mitotic arrestants Vinca alkaloids; colchicine (alkaloid); and podophyllin
Prophase Nucleolus disperses throughout the nucleus and the centrioles migrate to opposite poles
Prometaphase Nuclear envelope breaks down in most organisms
Five stages of Prophase I of Meiosis I Leptonema, Zygonema, Pachynema, Diplonema, and Diakinesis
Leptotene Stage Nuclear chromatin begins to condense, but chromosomes are not yet evident, the telomeres are attached to the nuclear envelope, and the cell has an enlarged nucleus and finely dispersed chromatin
Zygotene Stage Synapsis (homologous chromosomes lie next to and attach to each other) occurs (bivalents), synaptonemal complex forms where crossing over can occur, and the sex vesicle can be seen
Pachytene Stage Bivalents shorten and become thick, crossing over occurs, and chromomeres of the G-band patterns of mitosis prometaphase chromosomes can be discerned; bivalents are known as tetrads
Diplotene Stage Nucleolus detaches from its associated bivalents and bivalent chromosomes begin to separate as their centromeres pull them apart, but are still attached at chiasmata (sites of crossing over); end of sex vesicle
Diakinesis Stage Occurs in males: chiasmata move toward ends of the bivalents, nucleolus dissipates, and nuclear envelope disappears; females: meiosis halted in diplotene or dictyotene stage until ovulation
Created by: MorganRiso