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what is dna
- deoxyribonucleic acid
- carries hereditary information
- dna and proteins make up the chromosomes of cells
- viruses have RNa
- the variability inherent in dna forms the basis of natural selection and life's diversity
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what are the characteristics of dna
- double stranded, double helix
- composed of 4 types of nucleotides
- has deoxyribose sugar
- stored in nucleus
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what are the characteristics of rna
- single stranded
- has uracil instead of thymine
- has ribose sugar
- can leave the nucleus
- 3 types (mRNA, tRNA, rRNA)
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describe the structure of dna
- double helix
- two spiraling chains of necleotides
- held together by complementary base pairs
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what is dna made out of
- two strands that run antiparallel so proper hydrogen bonds between bases can form
- deoxyribose sugar
- phosphate group
- nitrogenous base
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what did phoebus levine discover in 1929
- deoxyribose is present in nucleic acids
- dna is made out of:
- -deoxyribose sugar
- phosphate grou
- one of four nitrogenous bases
- dna and rna are distinct nucleic acids but composed of nucleotides
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what did erwin chargoff discover in 1950
- broke down purified dna into its four nitrogenous bases
- -adenine=thymine
- -guanine=cytosine
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what did alfred hersey and martha chase discover in 1952
showed that viral dna directs the replication of new viruses
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what did rosalind watkins and maurice wilkins do
- took x-ray images of dna
- dna has a helical shape
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what did james watson and francis crick discover in 1953
- described the 3 dimensional structure of dna as a double helix
- two spiraling strands held together by complimentary base pairs
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which nitrogenous bases pair together
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which nitrogenous bases are purine (2 carbon ring)
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which nitrogenous bases are pyrimidine (1 carbon ring)
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what is nucleic acid
long, single or double stranded molecules composed of nucleotides (dna/rna)
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what is semi-conservative dna replication
- there is an original strand that acts as a template for each new strand
- half of the dna is kept and half is new
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what is the functions of nucleic acids
- carry genes that determine an organism's characteristics
- transmit species traits between generations
- control the production of cell's proteins, enzymes and hormones
- indirectly controls all cell functions, determines cell structure and activities
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nitrogen bases are held together by what
hydrogen bonds
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what are the dna replication steps
- 1. enzymes unwind dna to expose the two original strands
- 2. dna polymerase uses the two strands as templates to make complementary strands
- 3. new nucleotides will pair with exposed dna
- 4. the two resulting double-helix molecules coil up to form two chromatids in the chromosome
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what is a nucleotide made of
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why is dna replication essential
- cells duplicating
- organisms growing
- baby > adult
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describe protein synthesis
proteins are macromolecules made from amino acids and joined by covalent peptide bonds
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what are the functions of proteins
- build new cells and repair damaged ones
- cell membrane - structure
- skeleton - collagen, cartilage, ligaments, tendons
- muscle - cardiac, skeletal, smooth
- hormones - transmit signals
- antibodies - protection
- pigments - skin, blood, hair
- enzymes - control chemical reactions
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what are the 2 steps of protein synthesis
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what are the steps in transcription
- 1. RNA polymerase attaches to DNa and opens it at a certain spot
- 2. free-floating RNA necleotide bases will pair with exposed DNA nitrogenous vases
- 3. new mRNa strand leaves the nucleus and begins traveling to the cytoplasm for protein synthesis
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what are the steps in translation
- 1. ribosomes binds to the mRNA
- 2. mRNA has a start codon (methionine) that attaches to an anticodon on tRNA
- 3. the amino acid attacheswhen the first codon is read, the mRNA moves over so that the next codon can be read
- 4. a second tRNA anticodon will come and attach to mRNa codon
- 5. process continues until a stop codon is reached
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what are the 3 main types of rna
- messenger RNA (mRNA)
- transfer RNA (tRNA)
- ribosomal RNA (rRNA)
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describe messenger rna
- formed in the nucleus but functions in cytoplasm
- forms from translated dna
- nucleus > ribosomes
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describe transfer rna
- formed in nucleus but functions in cytoplasm
- translates codons into amino acids which for a protein sequence
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describe ribosomal rna
- in the ribosome
- translates mRNA codons that specify what amino acid is required and what order it is
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define codon
sequences of 3 nitrogenous bases
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define anticodon
anticodon on tRNA will base pair with a codon on mRNA base on what amino acid it codes for
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