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32 Cards in this Set
- Front
- Back
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What is the prominent structure in cells and stores genetic information in the form of DNA?
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the nucleus
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What specifies the protiens in a cell?
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DNA, with RNA
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What have many specific functions in cells, and help determine a cell's specificity?
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proteins
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If every cell in the body contains the same genes, how are they different?
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each type of cell has certain genes (which are segments of DNA) turned on, while others are turned off.
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When you look at the nucleus, even in an electron microscope, why don't you see DNA molecules?
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You see dispersed "chromatin" (a combination of DNA molecules and proteins that make up the chromosomes
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What is chromatin?
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is a mass of genetic material composed of DNA and proteins that condense to form chromosomes
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What are chromosomes?
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condensed thread of DNA
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What does each chromosome contain?
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A DNA molecule and associated proteins.
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Just before a cell divides, what does chromatin do?
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undergoes coiling into rodlike structures called chromosomes
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What is chromatin immersed in?
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nuceloplasm
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How is a nucleoplasm different than cytoplasm?
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A difference in pH
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What are nucleoli?
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one or more dark regions of chromatin, where another type of RNA, called ribosomal RNA (rRNA), is produced, and where rRNA joins with proteins to form the subunits of ribosomes.
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Where does rRNA join with proteins to form the subunits of ribosomes?
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in the nucleoli which are one or more dark regions of the chromatin
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What is rRNA?
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ribosomal RNA joins with proteins to form the subunits of ribosomes.
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What is the nucleus separated from the cytoplasm by, what is it called?
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A double membrane known as the "nuclear envelope"
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What is the nuclear envelope continuous with?
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The Endoplasmic reticulum (ER), a membranous system of saccules and channels
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What is the endoplasmic reticulum?
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a membranous system of saccules and channels
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What does the nuclear envelop have to permit the passage of ribosomal subunits out of the nucleus, while allowing proteins to enter into the nucleus?
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Nuclear pores
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What is the function of the nuclear pore and where are they?
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permits the passage of ribosomal subunits out of the nucleus, while allowing proteins to enter into the nucleus...they are located on the nuclear envelope
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What is a Barr body?
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An inactivated female X chromosome because females have two X genes, one of them is inactivated
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What is meant by the female mosaic?
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Some of a woman's cells have inactivated the maternal X chromosome and other cells have inactivated the paternal X chromosome
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Problems wiht the inactivation of the X chromosome in humans could be linked to the development of what?
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cancer such as breast cancer
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Woman who contain one defective copy of the gene BRCA1could have what?
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a Greatly increased risk of developing breast and ovarian cancer
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What gene is responsible for an increased risk in the development of breast and ovarian cancer?
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BRCA1
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Why does an increased cancer risk occur when involved with gene expression?
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Because abnormal BRCA1 protein can neither inactivate the X chromosome, nor function as a tumor suppressor.
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What are Ribosomes?
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Organelles composed of proteins and rRNA ribosomal ribonucleic acids
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What are organelles composed of proteins and rRNA?
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ribosomes
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Where does protein synthesis occur?
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At the ribosomes (protein factories of the cell) at the rough ER
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Where are ribosomes often attached?
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endoplasmic reticulum; they also occur free within the cytoplasm, either singly, or in groups called "polyribosomes"
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What are polyribosomes and where do they occur?
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groups of ribosomes that occur free within the cytoplasm
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What 2 places do the proteins produced by ribosomes attached to the ER eventually go?
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secreted from the cell or become part of the plasma membrane
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How did the proteins of the plasma membrane get there?
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those produced by ribosomes attached to the ER entually became part of the plasma membrane.
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