biology exam1 (part-2).docx - Biology Introduction to...

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BiologyIntroduction to Chromosomes and DNA PackagingWhen a cell divides, it is essential that the newcell (also known as thedaughter cell)contains the same genetic information as the oldcell (also known as theparent cell).This genetic information is our DNA, which ispackaged into chromosomes. Each chromosomecontains information about specific traits of anorganism.These chromosomes can be sorted intotwocategories:autosomes andsex chromosomes.DNA and ChromosomesWhen a cell divides in two, one of its main jobsis to make surethat each of the two new cellsgets a full, perfect copy of genetic material.Mistakes during copying, orunequal division ofthe genetic material between cells, can lead tocells that are unhealthy or non-functional such ascancer.DNA and GenomesDNA (deoxyribonucleic acid)is the geneticmaterial of living organisms. In humans,DNA isfound in almost all the cells of the body andprovides the instructions they need to grow,function, and respond to their environment.When a cell of thebody divides, it willpass ona copy of its DNA to each of its daughter cells.DNA is also passed on at the level of organisms,with the DNA in sperm and egg cells combiningto form a new organism that has genetic materialfrom both its parents. Physically speaking,DNAis a long string of paired chemical units(nucleotides)that come in four different types,and itcarries information organized into unitscalledgenes.Genestypicallyprovideinstructions for making proteins, which givecellsandorganismstheirfunctionalcharacteristics.In eukaryotes such as plants and animals, thegreat majority of DNA is found in the nucleusand is callednuclear DNA.In bacteria andother prokaryotes, most of the DNA is found in acentral region of the cell called thenucleoid,which functions similarly to a nucleus but is notsurrounded by a membrane.Acell’s set of DNA is called itsgenome. Sinceall of the cells in an organism (with a fewexceptions) contain the same DNA, you can alsosay that an organism has its own genome, andsince the members of a species typically havesimilar genomes, you can also describe thegenome of a species. In general,when peoplerefer to the human genome, or any othereukaryotic genome, they mean the set of DNAfound in the nucleus (that is, thenucleargenome).ChromosomesEach species has its own characteristic numberof chromosomes.Humans, for instance, have46 chromosomesin a typical body cell, whiledogs have 78. Like many species of animals andplants,humans arediploid (2n),meaning thatmost of their chromosomes come in matchedsets known ashomologous pairs. Thus,the 46chromosomes of a human cell are organized into23 pairs, and the two members ofeach pair aresaid to behomologuesof one another (with theslight exception of the X and Y chromosomes;see below).

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Term
Summer
Professor
JAINAH ROSE GUBAC
Tags
Cell Cycle, Mitosis, metaphase plate

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