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20 Cards in this Set
- Front
- Back
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a. What is a nucleotide? Why are nucleotides important, that is, what do your cells use them for?
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A subunit of a nucleic acid. Contains a 5-carbon sugar, a phosphate, and a nitrogenous base. Our cells use them for DNA & RNA, which store our genetic information
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Label the three main components (phosphate, sugar, nitrogen base) of the simplified representation of a nucleotide below.
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phosphate, sugar, nitrogen base
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c. Indicate the nitrogen bases found in DNA and RNA by completing the table below.
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Nitrogen Bases Found in DNA Nitrogen Bases found in RNA
Adenine Adenine Thymine Uracil Guanine Guanine Cytosine Cytosine |
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Why is it DNA replication necessary for all organisms on earth today?
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DNA replication is necessary so that cells can divide for growth and repair. Replication also allows genetic information to be passed from parent to offspring during the division.
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When during the cell cycle does DNA replication occur?
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S phase
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Name the enzyme responsible for lengthening each strand during DNA replication by repeatedly adding nucleotides to the end of each strand.
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DNA polymerase
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b. How does this enzyme “know” which nucleotide to use during DNA replication—that is, what “rules” does the enzyme follow?
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Adenine pairs with Thymine, Guanine pairs with Cytosine
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c. Name the enzyme that proofreads and corrects any errors it finds in the DNA strands after the completion of DNA replication.
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DNA polymerase
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d. What is a mutation? What are the four causes?
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Any change in the nucleotide sequence of DNA. The first cause is random errors during the replication process, as when DNA polymerase miss-matches a base pair. Replication occurs very fast and not all mistakes are corrected by proof-reading. The other three casues are viruses, toxins, and radiation.
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As in mitosis, the chromosomes are duplicated prior to the start of meiosis I. How many duplicated chromosomes will there be in a human “pregamete” cell just before the start of meiosis I?
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46 duplicated chromosomes. (23 homologous pairs, and each chromosome is replicated, so it looks like an “X”)
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b. How many DNA molecules are in a human “pre-gamete” cell just before the start of meiosis I?
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92 DNA molecules
During DNA replication, we start with a single molecule of double-stranded DNA. We end with two molecules of double-stranded DNA. the daughter molecules are exact copies of one another and they are attached at a centromere, which mean they are still considered 1 chromosome. Thus for this question we have 46 duplicated chromosomes, which means we have 92 DNA molecules. This would be the same as asking how many sister chromatids to we have (92). |
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c. Just after meiosis II and cytokinesis (the division of the cytoplasm) how many chromosomes are there in each gamete
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23. Meiosis results in ½ the number of chromosomes as the parent cell. Remember – Any time you see the word “gamete,” think about and egg or a sperm. They must have ½ the number of chromosomes because they get together to make a regular diploid body cell (the zygote).
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d. Just after meiosis II and cytokinesis how many DNA molecules are there in each gamete
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23. Remember that in Anaphase II, sister chromatids split, and so each of the resulting 4 daughter cells has 23 unreplicated chromosomes.
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Explain why AZT prevents another nucleotide from being added to a growing DNA strand and then explain how AZT will affect DNA replication.
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The N3 portion of AZT disrupts the sugar-phosphate backbone & so another nucleotide cannot bond properly to the growing strand. The replication of the DNA molecule will be discontinuous – it will have “nicks” that it cannot repair, resulting in a damaged chromosome.
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Fill in the following spaces concerning the “central dogma” of biology. Use the following terms only once: (phenotype, nucleotides, DNA, amino acids, protein, shape ) A gene is a section of ______________ that contains the code for the synthesis of one particular __________________. The order of ____________________________ in a gene determines the order of nucelotides in mRNA, which determines the order of __________________________ in the protein the gene codes for. This order controls the ___________________ of the protein, which in turn determines the function of that protein. An organism’s genotype determines the kind of proteins an organism can make. These proteins determine an organism’s _________________________________.
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A gene is a section of ___DNA____________ that contains the code for the synthesis of one particular ______protein_____________. The order of ______________nucleotides______________ in a gene determines the order of nucelotides in mRNA, which determines the order of ______amino acids____________________ in the protein the gene codes for. This order controls the ____________shape__________ of the protein, which in turn determines the function of that protein. An organism’s genotype determines the kind of proteins an organism can make. These proteins determine an organism’s _____________________phenotype____________
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differences in RNA and DNA by completing the table below
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DNA RNA
Number of Strands 2 1 Name of sugar in nucleotides Deoxyribose ribose Bases present ATCG AUCG Where produced in cell nucleus nucleus Where found in cell nucleus mRNA: nucleus, the cytoplasm (at ribosomes on rough ER tRNA: cytoplasm rRNA: ribosomes Name of process that makes it replication transcription |
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Transcription
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takes place in the nucleus, requires: DNA, the subunits for RNA (ribose, phosphate, and AUGC), RNA polymerase.
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Translation
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takes place in the cytoplasm, at the ribosomes on the rough ER. Requires: Ribosomes, mRNA, tRNA, amino acids. We did not discuss the enzymes involved in translation
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Transcription step
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Initiation - RNA polymerase enzyme binds to the promotor (section of DNA indicating “start of a gene”)
2. Elongation – RNA polymerase catalyzes base pairing on the template strand (U-A, G-C) 3. Termination – RNA polymerase reaches the “stop” sequence and the new mRNA is released. 4. mRNA processing – non-coding regions of the mRNA are removed and the mRNA leaves the nucleus |
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Translation step
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1. Initiation – mRNA start codon binds to tRNA anticodon; Ribosome binds to both
2. Elongation – tRNA brings specific AAs to the ribosome as mRNA passes through the ribosome (codon – anticodon recognition) Polypeptide chain forms 3. Termination – Ribosome reads an mRNA stop codon (no tRNA with anticodon). mRNA and protein detach from the ribosome |
