SI 3.2 DNA Protéine Synthesis Mutations PDF

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Biopsychology Worksheet 3.2 – DNA, Protein Synthesis, & Mutations! 1. DNA stands for: deoxyribonucleic acid . 2. DNA is made up of four different nucleotide bases: adenine, thymine , cytesine, & guanine. If DNA were a ladder, these bases would make up the rungs. The sides of the ladder are made of phosphate sugar bonds. 2. How do the four bases pair up to make the double helix structure? adenine pairs with thymine and cytosine pairs with guanine 3. DNA complementary base pairing practice: Fill in the blanks to create complementary strands of DNA: Strand 1: ATT ACG CAT CTG GAG Strand 2: TAA TGC GTA GAC CTC 4. The two main functions of DNA are __________________ and ______________________. 5. Protein synthesis (overview): Nucleotide bases come together to make codons, which code for amino acids, which some together to make polypeptide chain. 3 nucleotide bases make up a codon On codon codes for one amino acid Many codons (which all code for one Amino acid) make up polypeptide chain Polypeptide chain makes up protein 6. Protein synthesis (down and dirty): The double-stranded DNA is split down the middle and one strand, the coding strand, is copied into mRNA (aka messenger RNA). The way that the coding strand is copied is by matching up the complementary bases of the opposite strand. Coding Strand: A A T G C C C G T T T A Other Strand: T T A C G G G C A A A T To copy the coding strand, you find the complements of the “other strand.” Try it: mRNA Strand: This process is called transcription. All we really did was make a copy of the coding strand, but we had to do it by finding the opposites of the bases in the “other strand” NOTE: In mRNA, uracil replaces thymine! Once the DNA has been transcribed into mRNA, tRNA (aka __________ RNA) connects the appropriate amino acids together in a process called translation. Together these amino acids build proteins/polypeptide chains, which create all of our body, including the brain.

7. Take a deep breath!!! 8. True/False __f__ All genetic mutations result in horrible effects. __f__ A chromosome is just DNA. __f__ Protein synthesis takes place in the nucleus of the cell.takes place in ribosomes __t__ The bases of DNA compose the genetic code. 9. Matching! __F__ mRNA

a. “Read” mRNA during translation

_G___ tRNA

b. mRNA

__H__ Protein/polypeptide chain

c. Do not code for proteins; stay in nucleus

__E__ Codons

d. Code for proteins; leaves the nucleus

__C__ Introns

e. Sequence of 3 nucleotides

__D__ Exons

f. Transcription

__A__ Ribosomes

g. Translation

__B__ Uracil

h. Sequence of amino acids

10. What are mutations? How do they happen? Replication errors - different form of allele -> Can happen during meisos, mitosis, or replication. We think of all mutations as bad, but that isnt neckssarily true, some dont do anything. Mutations passed on through gametes 11. What is polymorphism? Is it bad? Changes in DNA that result in different version of a gene(allele). Not bad, it gives us variation— has a neutral/good connotation. Example of polymorphism would be different colored eye. It is a mutation. We see them in the population very commonly.

12. What is a single base mutation? When one base letter changes, resulting in a completely different protien. A point mutation in which one letter is changed — one nucleateide base is changed —> (CAG-> TAG) This leads to a completely different codon, which codes for a completely different amino acid, thus changing the protien. 13. What would happen if you lost a single base? Frame shift of nucleotide bases Can be very hazardous. Its doing the wrong thing and just keeps going, doesn’t know when to stop.

Frame shift deletion: missing a nudleotide base, and from that point on, the codons sequences are messed up (either transcribed wrong by MRNA or translated wrong by TRNA) You can have a frame shift insertion: inserting a nucleitide base. From that point on, the codon sequences are messed up (either transcribed wrong or translated wrong by TRNA) 14. What is a triplet repeat? What are the effects? Codon is repeated beyond normal # of repeats. • When replication occurs. Have too many amino acids • May (not) be issue depending on type of a.a. & number of repeats • 5at HD(huntington disease) = triplet repeat —> build up at a.a. in brain —> kills cells in basal ganglia and cortex • Number of repeats increased and number of repeats =

Codon is repeated beyond it normal # of repears. So you have too many codons repeating, which leads to too many amino acids being coded for. It may not be an issue but depending on what type of amino acid is being repeated BUT In Huntingtons disease, they have a large number of CCG codon repeats (about 100). This repeat leads to excessive amino acids being coded for through transcription and translation, which leads to a buildup of amino acids in the brain (in basal ganglia and cortex) The more repeats they have, the earlier the onset of HD and the more severe it will be. So someone who gets it in their 30’s might have a larger number of repeats, whereas someone who gets it in their 40’s would have less repeats....