UNIT 4. DNA, RNA, and Gene Expression

Transcription

1 UNIT 4 DNA, RNA, and Gene Expression

2 DNA STRUCTURE DNA is the primary material that causes recognizable, inheritable characteristics in related groups of organisms. DNA is the GENETIC MATERIAL Contain genes which are segments of DNA which code for specific traits. DNA is a relatively simple molecule Composed of only four different subunits: adenine, guanine, thymine, and cytosine (we will talk more about these later)

3 DNA STRUCTURE CONT. James Watson and Francis Crick discovered the structure of DNA. A winding Staircase: A DNA molecule is shaped like a spiral staircase and is composed of two parallel strands of linked subunits. Known as a double helix Each subunit is called a nucleotide. Each nucleotide is made up of three parts: a phosphate group, a five-carbon sugar, and a nitrogen base. The phosphate group and the five-carbon sugar link together to form the backbone of the DNA

4 A NUCLEOTIDE Deoxyribose Can be Adenine, Thymine, Guanine, Cytosine

5 THE STRUCTURE OF DNA The structure of DNA is very important The information in DNA is contained in the order of the bases (adenine, thymine, guanine, cytosine)

6 BASE-PAIRING RULES Adenine always pairs with thymine, and guanine always pairs with cytosine to connect each side of the helix. These bases are held together by weak hydrogen bonds.

7 THE CELL CYCLE: DNA REPLICATION

8 DNA REPLICATION When cells divide, each new cell contains an exact copy of the original cell s DNA. What is the name of this process? Remember DNA is always made of two strands of complementary base pairs. The process of making a copy of DNA is called DNA Replication DNA molecule unwinds, two sides split apart (splitting hydrogen bonds), new nucleotides are added to each side until two identical sequences result.

9 DNA REPLICATION CONT. The location where the DNA separates is called the replication fork. At the replication fork, new nucleotide bases are added.

10 REPLICATION PROTEINS During the replication of DNA, many proteins form a machinelike complex of moving parts LIKE A FACTORY!!!!!! DNA Helicase Protein that unwinds the DNA double helix during replication. DNA Polymerase Aids in the formation of the new DNA sequences. At the replication fork, DNA Polymerase moves along the strands adding nucleotides to produce the new double helix. What if DNA polymerase messes up??? Oops mutations Cancer

11 THE BACKBONE OF DNA CONSISTS OF: A. Deoxyribose Sugar only B. Phosphate only C. Deoxyribose Sugar and Phosphate D. Adenine, Thymine, Cytosine, and Guanine

12 WHICH OF THE FOLLOWING LISTS BOTH PURINES: A. Guanine and Cytosine B. Adenine and Thymine C. Thymine and Guanine D. Adenine and Guanine

13 THE REPLICATION PROTEIN INVOLVED IN REASSEMBLY OF TWO NEW DNA STRANDS: A. DNA Helicase B. DNA Polymerase C. DNA Ribase D. DNA Phosphase

14 THE REPLICATION PROTEIN INVOLVED IN UNZIPPING AND UNWINDING PARENT DNA A. DNA Helicase B. DNA Polymerase C. DNA Ribase D. DNA Phosphase

15 NITROGEN BASES ARE HELD TOGETHER BY WHICH BOND TYPE A. Covalent B. Ionic C. Sulfuric D. Hydrogen

16 EOC: A NUCLEOTIDE IS COMPOSED OF SUGAR, A PHOSPHATE GROUP, AND WHICH OF THE FOLLOWING? A. Amino Acid B. Fatty acids C. Glycerol D. Nitrogenous Base

17 EOC: CHARGAFF S RULE STATES THAT IN A GIVEN STRAND OF DNA, THE PERCENTAGE OF ADENINE WILL EQUAL THE PERCENTAGE OF THYMINE. IF A SEGMENT OF DNA WAS COMPOSED OF 23% A, WHAT PERCENT OF T WILL THE SEGMENT CONTAIN? A. 77% B. 26% C. 23% D. 99%

18 GENE EXPRESSION DNA does not directly make proteins. RNA is essential in taking the genetic information from DNA and building proteins! Genes from DNA produce proteins at the RIBOSOME, but this cannot be completed without RNA!

19 TRANSCRIPTION: DNA TO RNA The first stage making RNA from the information in DNA Called TRANSCRIPTION You can think of transcription as copying notes from the board (DNA) to a notebook (RNA) DNA vs. RNA DNA Deoxyribose sugar, phosphate group, nucleotide Double stranded Adenine (A), Cytosine (C), Guanine (G), Thymine (T) RNA Ribose sugar, phosphate group, nucleotide Single stranded Adenine (A), Cytosine (C), Guanine (G), Uracil (U)

20 MESSENGER RNA (MRNA) Messenger RNA (mrna) When DNA is transcribed into RNA, mrna is the type of RNA that is produced. The mrna carries instructions for making a protein from a gene and delivers them to ribosomes.

21 READING THE GENE Transcription begins with a molecule called RNA polymerase that unwinds and locates a start codon. mrna molecule comes in at that locations and starts producing the complementary RNA molecule. RNA polymerase eventually reaches a stop codon where the mrna stops getting longer.

22 INSTEAD OF CONTAINING THE BASE THYMINE, RNA CONTAINS THE BASE: A. Uracil B. Catalase C. Pepsin D. Helicase E. Polymerase

23 WHICH OF THE FOLLOWING WOULD DESCRIBE A SIMILARITY BETWEEN DNA AND RNA? A. Made of a single strand of nucleotides B. Contain the base Uracil C. Leaves the nucleus through nuclear pores D. Contains phosphate in its backbone E. Contain the base Thymine

24 TRANSLATION: RNA TO PROTEINS Uses information in RNA to make a specific protein. mrna codes for specific amino acids, that, when linked together, form proteins.

25 TRANSFER RNA (TRNA) During translation, trna reads the mrna sequence. trna has amino acids connected to them Attach these amino acids to a growing protein chain

26 BASED ON THE DNA SEQUENCE : ATCTGA, WHAT IS THE CORRECT COMPLIMENTARY MRNA SEQUENCE? A. TAGACT B. CGCGCT C. UAGACU D. UAGACT

27 THE PROTEIN THAT UNWINDS DNA TO ALLOW FOR TRANSCRIPTION IS CALLED: A. DNA Helicase B. DNA Polymerase C. RNA Polymerase D. RNA Helicase

28 THE PROCESS OF TRANSCRIPTION PRODUCES: A. trna B. DNA C. mrna D. Amino Acids

29 THE PROCESS OF TRANSLATION PRODUCES: A. Amino Acid Chain B. trna C. mrna D. DNA

30 BASED ON THE MRNA SEQUENCE UCG, WHAT IS THE CORRECT ANTICODON? A. AGC B. ACG C. TGC D. TCG

31 BASED ON THE DNA SEQUENCE AAG, WHAT IS THE CORRECT ANTICODON? A. TTC B. UUC C. AAG D. UUA

32 NAME THE AMINO ACID CODED FOR BY THE FOLLOWING CODON: GUC A. Phenylalanine B. Valine C. Serine D. Leucine

33 NAME THE AMINO ACID CODED FOR BY THE FOLLOWING CODON: ACA A. Valine B. Tyrosine C. Serine D. Threonine

34 EOC: WHICH OF THE FOLLOWING MRNA SEQUENCES CODES FOR VAL-GLU-SER, RESPECTIVELY A. UGG AGG CUA B. GUA GGG AGC C. GUC GAA ACU D. GUG GAG AGC

35 JOINING AMINO ACIDS TOGETHER AT THE RIBOSOME PRODUCES: A. Carbohydrates B. Proteins C. Lipids D. Nucleic Acids

36 EOC: WHICH MUTATION IS SHOWN DNA-> ACC GTC ATT CGG MUTATED DNA-> ACC GTC ATT CAG G A. Frameshift Deletion B. Frameshift Insertion C. Point Mutation D. Polymerase Mutation

37 REGULATING GENE EXPRESSION How do butterflies develop from caterpillars? We know that every cell in an individual starts with the same genes. So, during a butterfly s lifetime, not every gene is always at work. Some genes are ON, while others are OFF. (Genetic Switch)

38 GENE EXPRESSION Cells have complex systems that regulate whether or not specific genes are expressed. Expression depends on the cell s needs and environment. This is called gene regulation. Accounts for changes during development.

39 OPERONS The major form of gene regulation in prokaryotes depends upon operons that respond to environmental factors. An operon is a gene regulation system in which DNA segments control the expression of a gene. Operons are common in bacteria, but uncommon in eukaryotes.

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41 SO HOW DOES A EUKARYOTE (YOU) REGULATE GENES? Like prokaryotic cells, eukaryotic cells have proteins that regulate transcription. Transcription factors interact with RNA polymerase to promote transcription. Some transcription factors act as activators, and some act as repressors. Activators can bind at enhancer DNA segments and when they interact with promotor region (where RNA polymerase attaches), transcription begins.

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