dna and protein synthesis
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DNA AND PROTEIN SYNTHESIS

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DNA AND PROTEIN SYNTHESIS. 2008. DNA (DEOXYRIBONUCLEIC ACID) Nucleic acid that composes chromosomes and carries genetic information. CHROMOSOME ORGANIZATION 1. A chromosome is an enormous strand of super coiled DNA.

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slide2
DNA (DEOXYRIBONUCLEIC ACID)
  • Nucleic acid that composes chromosomes and carries genetic information.
slide3
CHROMOSOME ORGANIZATION

1. A chromosome is an enormous strand of super coiled DNA.

2. Sections of DNA on the chromosome that code for proteins are called genes.

3. Noncoding sections of DNA are called “junk DNA” (regulatory or unknown function)

slide5
BUILDING BLOCKS OF DNA

Composed of nucleotides

  • Nucleotides contain three parts:

1. 5-Carbon Sugar (deoxyribose)

2. Phosphate Group

3. Nitrogen Base (four types, adenine, guanine, thymine and cytosine)

slide9
STRUCTURE OF DNA
  • Consists of two strands of nucleotides that form a twisted ladder (double helix)
  • Sugar and phosphate alternate along the sides of the ladder (linked by strong covalent bonds)
  • Pairs of nitrogen bases form the rungs of the ladder (linked by weak hydrogen bonds).
slide10
Specific base pairing arrangement (Chargaff’s Rule)

A-T : 2 hydrogen bonds

C-G : 3 hydrogen bonds

  • Nitrogen bases attach to the sugar portion of the side (NOT the phosphate)
  • Strands run in opposite directions
slide12
FUNCTION OF DNA
  • DNA codes for proteins (structural proteins, enzymes, and hormones)
  • information for building proteins is carried in the sequence of nitrogen bases
  • proteins determine physical and metabolic traits and regulate growth and development.
slide14
DNA REPLICATION

Process in which DNA is copied

slide15
PURPOSE OF DNA REPLICATION

Gives daughter cells produced by cell division a complete set of genetic information identical to the parent cell.

slide18
HOW REPLICATION OCCURS

1. Helicase enzymes unzip the parent strand by separating the nitrogen base pairs.

2. DNA polymerase pairs free DNA nucleotides with the exposed bases on both strands following the base pair rules.

  • each strand from the parent molecule serve as a template
slide19
3. Hydrogen bonds reform spontaneously sealing the two strands of each DNA molecule together.
slide20
RESULTS OF REPLICATION
  • Two molecules of DNA that are identical
  • Each is half old (strand from parent) and half new (strand synthesized by DNA polymerase)
slide22
RNA (RIBONUCLEIC ACID)

Nucleic acid involved in the synthesis of proteins

slide23
RNA STRUCTURE

Composed of nucleotides, but differs from DNA in three ways.

  • Single strand of nucleotides instead of double stranded
  • Has uracil instead of thymine
  • Contains ribose instead of deoxyribose
slide25
RNA FUNCTION

Three forms of RNA involved in protein synthesis

1. mRNA (messenger): copies instructions in DNA and carries these to the ribosome.

2. tRNA (transfer): carries amino acids to the ribosome.

3. rRNA (ribosomal): composes the ribosome.

slide26
PROTEIN SYNTHESIS

Cells build proteins following instructions coded in genes (DNA).

  • Consists of two parts, transcription and translation
slide27
TRANSCRIPTION

DNA is copied into a complementary strand of mRNA.

WHY?

  • DNA cannot leave the nucleus. Proteins are made in the cytoplasm. mRNA serves as a “messenger” and carries the protein building instructions to the ribosomes in the cytoplasm.
slide29
HOW TRANSCRIPTION OCCURS

1. RNA polymerase untwists and unzips a section of DNA (usually a single gene) from a chromosome.

slide30
2. RNA polymerase pairs free RNA nucleotides to the exposed bases of one of the DNA strands following base pair rules.
  • Uracil replaces thymine
  • Only 1 strand of DNA serves as a template, the other “hangs out”
slide33
RESULT OF TRANSCRIPTION

mRNA strand with instructions for building a protein that leaves the nucleus and goes to the cytoplasm.

slide34
TRANSCRIPTION EXAMPLE
  • Transcribe the following DNA Sequence in mRNA

TAC CGG ATC CTA GGA TCA

AUG GCC UAG GAU CCU AGU

slide35
PROTEINS

Structural and functional components of organisms.

  • Composed of amino acids
  • order of nucleotides in DNA determines order of amino acids in a protein
  • One gene codes for one protein
slide37
GENETIC CODE

The “language” that translates the sequence of nitrogen bases in DNA (mRNA) into the amino acids of a protein.

  • Codon = three nucleotides on DNA or mRNA
  • One codon specifies one amino acid
  • Some codons are redundant (code for the same amino acid)
  • The genetic code is universal to all organisms
slide39
DNA: TAC CTT GTG CAT GGG ATC

mRNA AUG GAA CAC GUA CCC UAG

A.A MET G.A HIS VAL PRO STOP

slide40
IMPORTANT CODONS
  • AUG = start translation (Met)
  • UAA, UAG, UGA= stop translation
slide41
TRANSLATION

Instructions in mRNA are used to build a protein

slide42
LOCATION OF TRANSLATION

ribosome (in the cytoplasm)

slide43
PROCESS OF TRANSLATION

1. mRNA binds to the ribosome.

2. Ribosome searches for start codon (AUG)

3. tRNA brings correct amino acid (methionine) to the ribosome.

  • Each tRNA carries one type of amino acid.
  • The anticodon (three nitrogen bases on tRNA) must complement codon for amino acid to be added to protein chain
slide44
4. ribosome reads next codon

5. tRNA’s continue lining up amino acids according to codons

6. peptide bonds link amino acids together

7. ribosome reaches STOP codon

  • Amino acid chain is released
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