EVOLUTION AND GENETICS
3.1.1: Explain the double-stranded, complementary nature of DNA as related to its function in the cell.
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DNA, or Deoxyribonucleic acid is made of nucleotides. These nucleotides are made of deoxyribose sugar, a phosphate, and one of four nitrogen bases; Thymine, Adenine, Guanine, and Cytosine. DNA is made of two strands. The nitrogen bases are joined by a loose hydrogen bond.
these nitrogen bases only pair in one way; Adenine with Thymine, and Guanine with Cytosine. DNA is in the shape of a double helix. The order in which these bases occur determines which proteins will be produced and therefore which traits will be expressed and the function of the cell. Before cell division to happen the DNA must first be replicated. First enzymes split the strands, then complimentary strands are formed for each side using the base pairing rule above. This results is two strands of DNA that are identical.
these nitrogen bases only pair in one way; Adenine with Thymine, and Guanine with Cytosine. DNA is in the shape of a double helix. The order in which these bases occur determines which proteins will be produced and therefore which traits will be expressed and the function of the cell. Before cell division to happen the DNA must first be replicated. First enzymes split the strands, then complimentary strands are formed for each side using the base pairing rule above. This results is two strands of DNA that are identical.
3.1.2: Explain how DNA and RNA code for proteins and determine traits.
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The synthesis of proteins requires multiple organelles. DNA acts as a blueprint for what proteins are to be made, but DNA cant leave the nucleus. However, RNA, or ribonucleic acid is able to pass in and out of the nucleus. So DNA is rewritten into messenger ribonucleic acid in a process called transcription. During the first part of transcription the double helix is unwound. Then a complimentary strand of RNA is formed using the base pairing rule for DNA, with the exception that Thymine is replaced with Uranine, The double helix is rewound and the RNA travels through the cytoplasm and arrives at a ribosome. The mRNA is broken up into codons, or groups of three nitrogen bases. Each codon codes for a specific amino acid. The next step is called translation. Transfer ribonucleic acid, or tRNA recognizes the needed amino acids and brings them to the ribosome. They are then attached using anticodons. This results in a polypeptide, or a chain or amino acids.
3.1.3: Explain how mutations in DNA that result from interactions with the environment (i.e. radiation and chemicals) or new combinations in existing genes lead to changes in function and phenotype.
Activities for 3.1transcription
http://learn.genetics.utah.edu/content/molecules/transcribe/ protein synthesis http://www.glencoe.com/sites/common_assets/science/virtual_labs/LS04/LS04.html |
Some times the DNA isn't replicated correctly, or the codons are read wrong and the wrong protein is created. These accidental variations are called mutations. There are three types of mutations that can occur in cells: addition, deletion, and insertion. When addition occurs, an extra nitrogen base is added to the sequence. This can greatly change the protein to be synthesized, or it can have no effect at all. Deletion is the removal of one of the nitrogen bases, as with addition this can greatly effect the protein being synthesized or have no effect. Insertion is where a base is replaced by another base.
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