CFA Review - Protein Synthesis & Genetics

​Let's Remember:

​DNA codes for proteins (which means)

• ​DNA holds the codes which are the instructions for making a protein

• ​Proteins form our tissues, hormones, and most importantly - our traits

• ​Traits - unique characteristics or quality

• Different ​nucleotide sequences lead to different traits

• ​DNA base pairing:

  • A=T (Adenosine =Thymine)

  • ​T=A (Thymine=Adenosine)

  • ​C=G (Cytosine=Guanine)

  • ​G=C (Guanine=Cytosine)

​Let's Recall:

​DNA is in the nucleus of a cell. It holds the instructions for what proteins need to be produced. DNA cannot leave the nucleus to give the instructions to the ribosomes because the double helix is too big. mRNA has to help.

​mRNA is a single stranded molecule that can leave the nucleus. It copies the instructions from DNA and leaves the nucleus through the nuclear pore and takes the instructions to the ribosome. This process is called Transcription.

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When mRNA copies the code from DNA it matches up the base pairs just like DNA does, but mRNA does not have Thymine, so Adenosine has to match with Uracil.

​Remember: T=A A=TU C=G G=C

​

DNA Strand: TAT GGT GAT GTG TAG

​RNA Strand: AUA CCA CUA CAC AUC

​​

​So, in Transcription DNA -> mRNA

​mRNA is produced

​Let's recall:

​mRNA delivers the copied message from DNA to the ribosome where proteins are made from amino acids.

​mRNA attaches to the ribosome and tRNA (transfer RNA) matches to the codons (3 letter sequences). Each codon is linked to an amino acid using the codon chart. Once the message has been translated into amino acids (a polypeptide chain) and ends with the STOP codon it is done and the protein is produced.

​A mutation is a change in the nucleotide sequence of DNA or RNA.

​ex.

​Original DNA strand: TAC ACC TTG GCG

​​Mutated DNA: TAC ATC TTG GCG

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​If a mutation occurs in a somatic (body) cell, the mutation will not be passed on to the offspring.

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​If a mutation occurs in a gamete (sex) cell, the mutation will pass on in their offspring.

​Insertion - an extra base is added/inserted

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Deletion - a base is lost or deleted

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Substitution - one base is substituted for another

​Things to remember:

• ​Genes are segments of DNA that code (provide instructions) for traits

• ​One gene codes for one trait

• ​When a gene is expressed (is seen) it is "turned on"

• ​Environmental factors can affect gene expression (temperature, light, pH, radiation, sunlight, toxins)

​Mitosis - division of somatic (body) cells creating 2 identical daughter cells

​diploid in number (46 chromosomes in each body cell)

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​Meiosis - division of gametes (sex) cells creating 4 different daughter cells

​haploid in number ( 23 chromosomes in each egg cell and 23 chromosomes in each sperm cell)

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​Crossing over increases genetic variation in offspring.