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17 Cards in this Set
- Front
- Back
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Which cells have nuclei and which don't?
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red blood cells and platelets do NOT a nucleus.
all other cells have them (WBC etc) |
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the nuclear membrane is supported and shaped by filamentous proteins called __1__. defects in these proteins cause __2__.
nuclei come in every imaginable shape, but the nucleus of one kind of cell usually has only one possible shape thus the nuclear shape is often an impt clue for identifying the cells you are looking at. |
lamin A (most impt), lamin B, and lamin C.
premature ageing -the nuclear membrane aka the nuclear envelope! yes they stain the color of that dye. |
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the ____ contains 99.7% of a cells DNA (the other 3% are in the mitochondria).
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nucleus
the nucleus stains the color of the dye. |
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how many base pairs of dna does a human cell have?
how many codons? |
6 billion
2 billion codons should code for 2 billion AA (bc only one strand of dna is read; they are read in pairs of 3) |
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intron vs exon
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intron="INtervening sequences" and are the dna that is NOT translated into proteins and makes up *~97% of the DNA*
exon="EXpressed sequences" and it is the dna in a gene that IS translated to protein. ONLY the exon encodes for a protein. *makes up only 3-5% of the DNA!* thus most DNA does not make RNA thus not making protein! |
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DNA?
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Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses.
DNA is divided into 46 chromsomes (23 homologous pairs). each chromosome contains one pair of complementary DNA molecules. DNA and its associated proteins are referred to as CHROMATIN. *DNA is not a good catalyst |
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describe and draw the parts of the cell NUCLEUS and size.
how many base pairs of DNA are there in a human cell and how many codons? |
*99.7% of DNA is in the nucleus via the chromosomes/chromatids.
*the nucleus stains and cells have ONLY one possible shape usually so the nuclear shape is an impt clue for identifying the cells you are looking at. *6 billion base pairs of DNA and since only one strand of DNA is read, 6 billion base paris contain 2 billion codons. b/w 3 and 5% of the DNA in a human cell appears to be used in genes. the DNA of a human cell codes for 60-100 million AA or 80,000 proteins, give or take 20,000. *the unit membranes (cell membrane) are 9nm thick and 20nm apart. *however, the nucleus has a diameter of 4-10um (micro=10^-6). if the nucleus is smaller than that it is HAPLOID and only has half the normal amount of DNA (ex: sperm heads). if a nucleus is larger than 10um it is POLYPLOID: the huge nucleus of a megakaryocyte contains 182,000,000,000 base pairs: 32 copies of the human genome. *Chromatin and Chromosomes - Packed inside the nucleus of every human cell is nearly 6 feet of DNA, which is divided into 46 individual molecules, one for each chromosome and each about 1.5 inches long. For DNA to function, it can't be crammed into the nucleus like a ball of string. Instead, it is combined with proteins and organized into a precise, compact structure, a dense string-like fiber called chromatin. *The Nucleolus - The nucleolus is a membrane-less organelle within the nucleus that manufactures ribosomes, the cell's protein-producing structures. Through the microscope, the nucleolus looks like a large dark spot within the nucleus. A nucleus may contain up to four nucleoli, but within each species the number of nucleoli is fixed. After a cell divides, a nucleolus is formed when chromosomes are brought together into nucleolar organizing regions. During cell division, the nucleolus disappears. |
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mitosis vs meiosis (main difference/product)
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mitosis-form two identical cells from one cell
meiosis-halves the genetic material – forms sex cells |
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describe the cell cycle and the beginning of it.
DNA makes RNA only during the ____ phases of the cell cycle? |
*CELL CYCLE- Model for what happens–One step has to be completed before moving on to the next interphase, mitosis, (cytokinesis).
*DNA makes RNA only during the *G phases* of the cell cycle. So TRANSCRIPTION occurs in these G-phases! ------------------------ *Interphase: time between divisions--consists of G1, S and G2 G1 – cell carries out normal/specialized functions short amount of time in rapidly dividing cells -Cell prepares proteins, lipids and carbohydrates - may be needed for division Cell is sensitive to external and internal signals ----------------------------- G0 – stops dividing. *most cells are in this stage most the time* Cells can exit the cell cycle from G1 and become “quiescent” - not really quiescent – just not dividing - cell continues to carry on functions (part of interphase b/w G1 and S phase) ----------------------------- SECOND PART OF INTERPHASE: S phase (synthesis of DNA aka REPLICATION) If cell is to divide, enters S phase *during S phase, the two complementary DNA molecules that are hydrogen bonded together to form a chromosome come apart, a few base pairs at a time. AT-GC pairing occurs and the new desoxyribonucleotides are linked together by DNA POLYMERASE to form new complementary strands of DNA. *the result is that each chromosome becomes two chromatids. each chromatid is half new material, but each chromatid has the same nucleotide sequence as the original chromosome. the chromatids are joined into one double-size chromosome at a region of NON-GENE DNA called the CENTROMERE.* - replicates genetic material - at the end has 2 copies of all genetic material ------------------------------ LAST PART OF INTERPHASE: G2 - (still part of interphase) (late interphase, cell checks for complete DNA replication) *the 92 chromatids of the G2 cell continue to transcribe RNA. After replication of DNA has occurred: cell makes proteins and extra membrane tubulin – a structural protein - makes microtubules used in mitosis to divide cell extra membrane stored as small vesicles increase cell surface area Is DNA completely replicated? DNA winds tighter - condensed mitosis- Separates replicated material into two cells ------------------------------ |
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DESCRIBE the 'central dogma' of molecular biology
what are the complementary bases of DNA/RNA? |
cental dogma: "DNA makes RNA; RNA makes protein"
*REPLICATION: DNA-->DNA *TRANSCRIPTION: DNA-->RNA (bc the base sequence of DNA must be copied into the less stable but more catlytic RNA bc DNA is not a good catalyst). This copying of the DNA base sequence onto a complementary strand of RNA is called transcription. *the complementary RNA has URACIL matching ADENINE on the DNA, CYTOSINE matching GUANINE on the DNA, ADENINE matching THYMINE on the DNA, and GUANINE matching CYTOSINE on the DNA.* "AT-GC, and replace T with U for RNA." *TRANSLATION: RNA-->PROTEIN *only a small fraction of any one cell's DNA makes RNA. liver cells transribe only the genes for liver proteins usually. Fibroblasts normally transcribe only the genes for fibroblasts. etc. unused genes may be almost permantnely inactivated by the methylation of CYTOSINE. genes may be temporarily inactivated by ionic bonding to basic proteins called HISTONES. |
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what are the different types of chromatin?
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*Chromatin is found in two varieties: euchromatin and heterochromatin
*Heterochromatin is a tightly packed form of DNA. Its major characteristic is that transcription is limited. *Euchromatin is a lightly packed form of chromatin that is rich in gene concentration, and is often (but not always) under active transcription. Unlike heterochromatin, it is found in both eukaryotes and prokaryotes. *DNA and its associated histones are referred to as HETEROCHROMATIN (which can't be transcribed). heterochromatin is more compact and stains more darkly than active DNA. the darkness of its nucleus is a guide to a cell's activity. |
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active nuclei contain __1__ nucleoli. a __2__ is a mass of ribosomal RNA waiting to leave the nucleus.
the genes for ribosomal RNA occur in groups on several chromosomes. each group of r-RNA is called a __3__. |
1) 1 to 3 nucleoli
2) nucleolus 3) nucleolar organizer. these approach each other and surround themselves with newly synthesized r-RNA to form a nucleolus. |
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What is mitosis and the result?
Mitosis is controlled by small proteins called ____. List the steps of mitosis. |
controlled by small proteins called CYCLINS.
mitosis is the equal division of the chromosomes into the nuclei of 2 daughter cells. you form two identical cells from one cell! the division is orchestrated by two CENTRIOLES. each centriole consists of 9 TRIPLETS of short microtubules arranged in a circle. the centrioles are at right angles to each other and next to the nucleus. *PMAT Prophase, metaphase, anaphase, telophase |
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describe prophase
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*during prophase of mitosis the chromatids become pleated like ribbon candy and this makes them appear short and thick. *RNA is no longer transcribed*. The edges of the pleats are linked by proteins called CONNEXIN and CONDENSIN. A pair of protein discs called KINETOCHORES attach to each centromere.
At the end of prophase the nuclear membrane breaks down and the cell's two centrioles move to opposite ends of the cell, and microtubules gro bw them to form a mitotic spindle. ----------------------------- OTHER INFO... Prophase (pro = before) DNA condenses – appears X-shape Centrosomes - organizes the mitotic spindle Centrosomes move to opposite sides of the cell MT originate from the centrosomes – asters MT extend and retract |
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describe metaphase
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during metaphase, more microtubules grow from the cytoplasm around the centrioles to the kinetochores of the double-size chromosomes. the pull of these microtubules lines the chromosomes up in the middle of the cell.
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describe anaphase
the ____ in the ____ does what? |
in anaphase, the dynein in the kinetochores pulls the new single-size chromosomes apart along the microtubules to form two new nuclei.
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describe telophase
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telophase is the division of the cytoplasm to form two new cells. the process of mitosis ensures that each daughter cell has the SAME genome as the other.
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