UNIT 6: DNA BIG IDEA: DNA contains the genetic information to produce proteins but must first be converted to RNA to do so

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Why do cells need DNA? DNA contains the information cells need to function and live. Two main roles for DNA are 1. Storing genetic info and to 2. “Read” and translated to make proteins

DNA Replication “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material” ~Watson and Crick

Why do cells need to replicate (copy) their DNA? To make new cells and make sure all new cells have a complete set of the genetic info

How do cells replicate their DNA? 1.The DNA double helix is unwound by an enzyme.

adds complementary nucleotides. 2.Another enzyme moves down the 2 original DNA strands and

3.Two separate DNA molecules are formed, each with one new strand and one old strand.

Replication Stats 6 billion base pairs per cell. All are replicated in a few hours. Mistake happens one per billion nucleotides.

Mistakes = Mutations Mutations are changes in the base sequence of the DNA molecules. This can have serious affects on genes and the functions of cells. Cancer is caused by mutations in DNA.

Mutagens Physical or chemical factor that increases the frequency of mutations. Examples: UV rays, X-rays, smoking

3 Types of Mutations Insertion Deletion Substitution

MUTATIONS

DO NOW: What words do you think of when you hear the term mutations?

Three Types 1.Substitute: one nitrogen base is substituted for another in the DNA strand Normal DNA: TAGCGCTA ATCGCGAT Mutated DNA: TAGCGCTA ATCTCGAT

Three Types Insertion: One nitrogen base is inserted or added to a DNA strand Normal DNA: TAGCGCTA ATCGCGAT Mutated DNA: TAGCGCTA ATTCGCGAT

Three Types 3. Deletion: one nitrogen base is deleted from the DNA strand Normal DNA: TAGCGCTA ATCGCGAT Mutated DNA: TAGCGCTA ATCGCAT

Substitution Examples Normal DNA:DNA with Mutation: AAA ATG CTTAAA ATG TTT mRNA: UUU UAC GAA UUU UAC AAAAmino Acid: Phe-Tyr-Glu Phe-Tyr-Lys

Create: 1.DNA strand with one base inserted 2.DNA strand with one base deleted How does this effect amino acid sequence?

Chromosomal Mutations Deletion: loss of a piece of chromosome

Mutation Type 2 & 3 Inversion: chromosomal segment breaks off, flips around backward, and reattaches Translocation: piece of one chromosome breaks off and reattaches to a nonhomologous chromosome

Mutation Type #4 Nondisjunction- chromosome fails to separate from it homologue

Protein Synthesis Transcription

DNA vs. RNA Single stranded Ribose sugar Uracil Anywhere Double stranded Deoxyribose sugar Thymine Nucleus

3 Types of RNA Messenger RNA (mRNA): Carries information from DNA to ribosome for________________. Transfer RNA (tRNA): Transport _________________. Ribosomal RNA (rRNA): makes up the _____________. protein synthesis amino acids ribosomes

Part 1:Steps of Transcription 1.An _________ attaches to a section of DNA, separating the two strands. 2.The enzyme moves down the DNA, building a strand of RNA that is __________________ to the DNA. 3.The enzyme reads a ________ code and the new strand of RNA is completed and moves into the _______________. enzyme complementary STOP cytoplasm

Protein Synthesis Translation

The genetic code The base sequence is read in groups of ____________________________. Each 3-nucleotide sequence is called a _________. Each codon encodes for a specific ____________or a ______or ______signal. three adjacent nucleotides codon amino acidstart stop

Amino Acid Anti-codon

Steps of Translation 1.mRNA attaches to a ____________. Amino acids floating in the cytoplasm are transported to the ribosome by _______. 2.The first tRNA binds to the ______ codon: AUG. ribosome tRNA start

3.Another tRNA binds to the next codon and carries the appropriate amino acid. A __________________ forms between the two amino acids. 4.The first tRNA leaves and the ribsome moves across the next __________. peptide bond codon

5.Another tRNA binds to the codon and attaches the corresponding amino acid. The __________________ chain continues to grow. 6.Finally, the ribosome reads the ___________________, and the polypeptide falls off the ribosome. polypeptide STOP codon

Amino acid tRNA ribosome mRNA polypeptide

The final step of protein synthesis: The polypeptide made at the end of translation, folds into the proper ________, becoming a functional ________. shape protein

The central dogma of biology DNA  RNA  protein