Chapter 12 DNA RNA Interest Grabber Section 12
Chapter 12 DNA & RNA
Interest Grabber Section 12 -1 l. Order! l. Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three of these units form a code. The order, or sequence, of a code and the type of code determine the meaning of the message. 1. On a sheet of paper, write the word cats. List the letters or units that make up the word cats. 2. Try rearranging the units to form other words. Remember that each new word can have only three units. Write each word on your paper, and then add a definition for each word. 3. Did any of the codes you formed have the same meaning? 4. How do you think changing the order of the nucleotides in the DNA codon changes the codon’s message?
Interest Grabber Section 12 -2 l A Perfect Copy l When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.
Section 12 -2 1. On a sheet of paper, draw a curving or zigzagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper. 2. Hold the papers side by side, and compare the lines. Do they look the same? 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? 4. How could you use the original paper to draw exact copies of the line without tracing it? 5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?
II. Chromosomes & DNA Replication l A-DNA & Chromosomes ¡ In cytoplasm in prokaryotes ¡ In ____________found in cell nucleus in the form of a number of chromosomes(46 humans, 8 Drosophilia and 22 Sequoia trees) eukaryotes
l 1 --DNA length ¡ 1. 6 mm in E. coli(has 4, 639, 221 base pairs)--obviously it must be tightly folded
l 2 -Chromosome Structure ¡ Eukaryotic cells have about 1000 times as many base pairs of DNA than a bacterium ¡ Humans cells have ~ 1 m DNA ¡ Eukaryotic chromosomes contain DNA and a protein , which together make ___________-consisting of DNA tightly packed around proteins called histones chromatin
DNA and histone together make beadlike_______________ ¡ Nucleosomes pack together to make thick fibers, drawn together during mitosis…also separating l Role of nucleosomes-fold great lengths of DNA into tiny spaces ¡ nucleosomes
Prokaryotic Chromosome Structure Section 12 -2 Chromosome E. coli bacterium Bases on the chromosome
Figure 12 -10 Chromosome Structure of Eukaryotes Section 12 -2 Chromosome Nucleosome DNA double helix Coils Supercoils Histones
B. DNA Replication l l l Each strand of DNA double helix has all the info to______________by base pairing Strands are complementary In prokaryotes, this begins @single point and proceeds-often in 2 directions In Eukaryotes, DNA replication begins @ 100’s of places, going both directions until complete _____________is where replication occurs Reconstruct the other half Replication fork
l 1 -Duplicating DNA ¡ _____________or duplication of DNA happens before cell division---ensuring each cell has a complete set of DNA molecules ¡ Each strand of a double helix serves as a ___________or model for new strand ¡ A pairs w/ T and C w/ G template replication
l 2 -How Replication Occurs ¡ Carried out by a series of enzymes that unzip a molecule ¡ __________________ joins individual nucleotides to make a DNA molecule…. also proof reads the new strands DNA polymerase
Figure 12– 11 DNA Replication Section 12 -2 New strand Original strand DNA polymerase Growth Replication fork Nitrogenous bases Replication fork New strand Original strand
III. RNA & Protein Synthesis l l ¡ ¡ The double helix structure explains how DNA is copied, but not how a gene works________are coded DNA instructions that control the production of protein in the cell. A) The structure of RNA Long chain of nucleotides 3 main differences between DNA & RNA: l 1 --Sugar is _________ l 2 ---Generally single-stranded l 3 ---RNA contains ________(U) in place of thymine (T) uracil genes ribose
B. Types of RNA ¡ ¡ Protein synthesis Main job=_________-ie the assembly of amino acids into proteins 3 Types: l __________(m. RNA)-carry copies for instructions from DNA to rest of cell l __________(r. RNA)-type of RNA that helps make up ribosomes, where proteins assembled l ________(t. RNA)transfers each amino acid to the ribosome as it is coded for on m. RNA. messenger ribosomal Transfer
Concept Map Section 12 -3 RNA can be Messenger RNA also called Ribosomal RNA which functions to m. RNA Carry instructions also called which functions to r. RNA Combine with proteins from to to make up DNA Ribosomes Transfer RNA also called t. RNA which functions to Bring amino acids to ribosome
C. Transcription-produces RNA molecules by copying part of nucleotide sequence of DNA into a complementary sequence in RNA ¡ ¡ Requires enzyme known as ____________________binds to DNA and separates DNA strands. Then uses one strand as template to make RNA The enzyme only binds to areas known as promoters-signals that indicate where to make RNA. Similar signals tell where to stop RNA-polymerase
Figure 12– 14 Transcription Section 12 -3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase RNA DNA
D. RNA editing ¡ ¡ ____________ in eukaryotic genes , sequences of nucleotides that ARE NOT involved in coding for proteins ____________-DNA sequence that does code for protein exons introns
E. Genetic Code polypeptide ___________-chain of amino acids=proteins codon ¡ _________-3 consecutive nucleotides that specify a specific amino acid l Example –UCGCACGGU reads UCG_CAC_GGU and codes for Serine-Histidine-Glycine ¡
The Genetic Code Section 12 -3
l Universal code l 64 possible 3 base codons l AUG can specify methionine or start codon l 3 stop codons that do not code for an amino acid
F. Translation ¡ ¡ ribosome ___________reads the instructions for the order in which amino acids should be joined by reading m. RNA translation ______________is the decoding of an m. RNA message into a polypeptide(protein) Before translation occurs, m. RNA is transcribed from DNA and released into cytoplasm _____________. Translation begins when m. RNA molecule in cytoplasm attaches to a ___________. ribosome
As each codon of the m. RNA moves through the t. RNA ribosome, _______brings in the proper, indicated amino acid and transferred to polypeptide chain ¡ Each t. RNA carries one kind of amino acid ¡ _________ is a group of 3 bases on a t. RNA that are complementary to a m. RNA codon ¡ Ribosome forms a _________bond between amino acids and breaks t. RNA bond releasing it ¡ Protein keeps growing until ribosome reaches stop codon on m. RNA ¡ peptide anticodon
Figure 12– 18 Translation Section 12 -3
Figure 12– 18 Translation (continued) Section 12 -3
IV. Mutations=___________ Changes in genetic material __ Gene mutation ¡ l l l A. ---Kinds of Mutations l 1) l ________________-changes in a single gene ___________________-changes in 1 or a few nucleotides-@ a single point in DNA-includes substitutions, insertions and deletions Substitutions usually affect no more than 1 amino acid __________________-insertions or deletions where the reading frame of the codon message is changed-can VERY much alter or even stop the function of a protein Point mutation Frameshift mutation
2)Chromosomal Mutations-change in the # or structure of chromosomes-can change the location of genes on chromosomes and /or number of copies of some genes. 4 types-1)Deletions-loss of all or part of a chromosome 2)_________-extra copies of a part of a chromosome 3)________reverse directions of parts of chromosomes 4)______-part of one chromosome breaks off and attaches to another l l l translocations duplication inversions
Gene Mutations: Substitution, Insertion, and Deletion Section 12 -4 Substitution Insertion Deletion
Figure 12– 20 Chromosomal Mutations Section 12 -4 Deletion Duplication Inversion Translocation
B. Significance of Mutations Many have no effect l Harmful effects include genetic disorders and cancer l ____________-contains extra set of chromosomes-bad in most cases but often helpful in PLANTS. l polyploidy
V. Gene Regulation l l l operon Only a fraction of a gene expressed at one time __________-group of genes that operate together ________-where repressor binds operon (when it)is turned off Operons not usually found in eukaryotes-these genes are usually controlled individually and regulation more complex---mainly because of cell specialization Hox genes-control differentiation of cells and tissues in the embryo operator
Typical Gene Structure Section 12 -5 Regulatory sites Promoter (RNA polymerase binding site) Start transcription DNA strand Stop transcription
Karyotypes
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