The structural and functional divergence of cells as they become specialized during a multicellular organism's development; dependent on the control of gene expression.
Deoxyribonucleic acid; the genetic material that carries information about an organism and is passed from parent to offspring. Because of its phosphate group it is tightly bound to 4 positively charged Histones(8 total) to form a nucleosome.
Histone Code Hypothesis
This hypothesis proposes that specific combinations of modifications, rather than the overall level of histone acetylation, determine chromatin configuration
The proteins called ____ that are responsible for the first level of DNA packing in chromatin . Its mass is approximately equal to that of DNA, and it largely consists of positive amino acids(arginine, lysine), its apparent conservation in Eukaryotic genomes signals its importance. 4 of these(H2A, H2B, H3, H4) (8 total)along with DNA form a nucleosome.
Basic structural unit of chromatin; core of four types of histone ( H2A, H2B, H3, H4)(2 of each) wrapped in DNA, and prevalent during Interphase, also called beads on a string, they are linked together by linker DNA, some parts are tightly condensed(Telomeres and Centromeres), 10nm.
After nucleosomes condense and link the 30 nm fiber gathers into thick supercoiled loops (80-100 nm). Tethered to protein scaffold of the (nuclear matrix)- regulates degree of supercoiling. Seen during Prophase, can become 300 nm
Densely staining condensed chromosomal regions, believed to be for the most part genetically inert, because transcription enzymes can't reach it. Darkly stained throughout the cell cycle. Usually consists of Telomeres and Centromeres
DNA that is loosely packed around histones. This DNA is more accessible to enzymes and the genes in euchromatin can be activated if needed. (True Chromatin)
Organisms made up of one or more cells that have a nucleus and membrane-bound organelles.
Differential Gene Expression
The expression of different sets of genes by cells with the same genome. Typically only about 20% of genes are expressed, however in highly differentiated cells(like muscle) even less is expressed.
The string between beads of DNA on histones. They are also wrapped around a single histone, called linker histone (H1) - may not really have to know..
A netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope
A period between two mitotic or meiotic divisions during which the cell grows, copies its DNA, and synthesizes proteins
The 2nd stage in mitosis or meiosis in which the duplicated chromosomes line up along the equatorial plate of the spindle
the beginning of an amino acid chain, identified by a free amino group, in the histones it protrudes outwards from the nucleosome, which are sometimes modified by the addition or removal of chemicals( acetylation, methylation)
Maintain sister chromatid cohesion prior to the anaphase stage. Site of kinetochore formation. Hence, they mediate chromosome migration during the anaphase stage. This process is essential to the separation of chromatids and thus the fidelity of chromosome distribution during cell division. (Few mistakes).
First and longest phase of mitosis, during which the chromosomes become visible and the centrioles separate and take up positions on the opposite sides of the nucleus
regions of cytoplasmic material that in animal cells contain structures called centrioles
large fluid vacuoles found olny in plants that support pressure of fluid against the cell wall which helps the cell stand upright
The percentage of DNA that actually codes for protein.
The process whereby genetic information flows from genes to proteins; the flow of genetic information from the genotype to the phenotype, usually regulated at the transcription leve;.
the attachment of acetyl groups (-COCH3) to certain amino acids(lysine, arginine) of histone proteins at the N Terminus, this neutralizes the positive charges(so less binding to necolosomes, the chromatin becomes less compact, and the DNA is more accessible for transcription
The addition of methyl groups (-CH3) to histone tails(N Terminus), promotes condensation of the chromatin and in effect discourages (discourages transcription)
The addition of methyl groups (—CH3) to bases of DNA after DNA synthesis(DIFFERENT from Histone Methylation); may serve as a long-term control of gene expression. Serves to limit expression, may act with other enzymes to recriut deacetylation enzymes, thus giving dual repression.
Phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent., related to DNA methylation
inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence of a genome, like DNA methylation, and histone methylation or acetylation
Transcription Initiation Complex
The completed assembly of transcription factors and RNA polymerase bound to a promoter. Assembled on the promoter sequende at the upstream end of the gene.
RNA Polymerase 2
In the nucleoplasm and makes a pre -mRNA and some snRNAs. snRNA's function in splicing out the introns. Part of the "Snurp's". Only one strand of DNA is used in transcription.
Segments of noncoding DNA that help regulate transcription of a gene by binding proteins called transcription factors.
collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription
Proximal Control Elements
Control elements located close to the promoter
Still do the same job of binding proteins to DNA so that transcription can take place
Increase rate of transcription
Distal Control Elements
(groups are called enhancers), can be far away (downstream) from gene or even located in an intron.
the more distance distal control elements, groups of which are called ________, may be thousands of nucleotides upstream or downstream of a gene or even within an intron
A transcription factor that binds to an enhancer and stimulates transcription of a gene.
Additional transcription factors that interact with proteins at the promoter to assemble the initiation complex
some specific transcription factors function as _________ to inhibit expression of a particular gene, can block the binding of activators to their control elements, or they can bind to their own control elements in an enhancer.
The recruitment of proteins by repressors that act to deacetylate histones leading to reduced transcription. Recruitment of mediator proteins is the most common mechanism for repression in Eukaryotes.
Alternative RNA Splicing
a type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns
Poly A Tail
The modified end of the 3' end (adenine base pairs) of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides., mRNA degradation typically begins with shortening of this.
In multicellular eukaryotes last hours, days or weeks; duration dictates the number of protein translated from them. Breakdown starts with enzymatic shortening of poly-A tail; triggers the removal of 5' cap by enzymes, followed by the consumption by of mRNA by nucleases.
Untranslated region; part of mature mRNA; not translated; upstream of start or downstream of stop, technically an exon, Neucleotide sequences at the 3` end of this molecule are thought to help determine the lifespan length of mRNA.
Small single-strand RNA molecules that bind to mRNA molecules to block certain parts' expression. They are formed from longer RNA procurers that fold back on itself forming a long hairpin structure held together by hydrogen bonds.
Enzyme that cleaves and processes double stranded RNA to produce siRNAs or miRNAs that are 21-25 nucleotids in length
technique to silence the expression of selected genes in nonmammalian organisms; uses synthetic double-stranded RNA molecules matching the sequence of a particular gene to trigger the breakdown of the gene's messenger RNA. done by (RNAi) due to siRNA.
the simultaneous regulation of numerous genes which is a form of transcriptional regulation, which involves the activation or inactivation of one or more protein factors(MRNA), Like in fertilization the activation of a protein factor initiates a burst of synthesis.