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15 Cards in this Set
- Front
- Back
What is the structure of DNA, where is DNA found & what is DNA made up of? |
*Double helix structure.
*Found in all cells except red blood cells.
*Made up of 4 bases.
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How is DNA adapted? |
*Stable molecules
*Hydrogen bonds which break easily
*Large structure = Lots of information
*Not easily corruptible structure |
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When & why does DNA replicate itself?
What breaks the hydrogen bonds in DNA? |
*Just before mitosis when the cell divides.
*To pass on information so the cell can make an exact copy of itself.
*Helicase breaks hydrogen bonds. |
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What is the structure of a nucleotide unit? |
*A phosphate - Phosphoric acid
*A sugar - Deoxyribose in DNA
*1 of 4 organic bases - Adenine, Guanine, Cytosine & Thymine {always contains Nitrogen & Carbon}. |
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What are nucleic acids made up of? |
*Polymers
*Individual unit - {Mono}nucleotide
*DNA is a type of nucleic acid. |
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What are purines and give examples of them? |
*Double ringed structure
*Adenine
*Guanine |
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What are pyrimidines and give examples of them? |
*Single ringed structure
*Thymine
*Cytosine |
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What are the two bonds in DNA, how do they occur & what are the pairing of the bases? |
*Base + Sugar - Glycosidic bond.
*Phosphate + Sugar - Ester bond.
*Condensation reaction is needed.
*Purines pair with pyrimidines - Adenine joins to Thymine & Cytosine joins to Guanine. |
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How much amino acids occur naturally, what is a triplet code & how many different combinations in triplet codons can be formed? |
*There are 20 naturally occuring amino acids.
*Triplet code is a sequence of 3 bases coding for a specific amino acid.
*4 bases -> 64 different combinations in triplet codons. |
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Outline the first nuclear division of meiosis? |
*Interphase I - Chromatin not visible & DNA & proteins replicated. *Prophase I - Chromosomes visible, homologous chromosomes join to form a bivalent & chromatids cross over. *Metaphase I - Bivalents line up on equator. *Anaphase I - Chromosomes separate. *Telophase I - Nuclei form, cell divides & have 2 chromosomes. |
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Outline the second nuclear division of meiosis? |
*Interphase II - Short, no DNA replication & chromosomes remain visible. *Prophase II - Centrioles replicate & move to new poles. *Metaphase II - Chromosomes line up on equator. *Anaphase II - Centromeres split & chromatids separate. *Telophase II - 4 haploid cells, 2 chromosomes each & cells usually stay together to form tetrad. |
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What is a gene, locus & allele? |
*Gene - A section of DNA that codes for a polypeptide.
*Locus - The position of a gene on a chromosome or DNA molecule.
*Allele - One of the different forms of a particular gene. |
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What are the two ways in which meiosis brings about genetic variation? |
*Independent segregation of homologous chromosomes.
*Recombination of homologous chromosomes by crossing over. |
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Explain independent segregation of homologous chromosomes. |
*During the first division, the chromosomes line up along its homologous partner. *They randomly place themselves in line. *1 pair of each will be passed on to each daughter cell. *The pair which goes in to each daughter cell depends on how the pairs are lined up. *Since the pairs lined up randomly, the combination of chromosomes is random. |
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Explain genetic recombination by crossing over. |
*During meiosis I, chromosomes line up alongside its homologous pair. *The chromatids of each pair become twisted around one another. *The twisting process causes tension and portions of chromatids break off. *Broken portions rejoin with the chromatids of their homologous partner - recombination. *Usually equivalent portions are exchanged - crossing over. |