chapter 12 dna & rna. interest grabber order! order! genes are made of dna, a large, complex...
Post on 17-Jan-2016
224 Views
Preview:
TRANSCRIPT
Chapter 12
DNA & RNA
Interest GrabberOrder! Order!
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.
Section 12-1
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 eachnew 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
A Perfect Copy
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
I
Section 12-2
1. On a sheet of paper, draw a curving or zig-zagging 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
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
1--DNA length 1.6 mm in E.coli(has 4,639,221 base pairs)---
obviously it must be tightly folded
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
Role of nucleosomes-fold great lengths of DNA into tiny spaces
nucleosomes
Chromosome
E. coli bacterium
Bases on the chromosome
Prokaryotic Chromosome StructureSection 12-2
Figure 12-10 Chromosome Structure of Eukaryotes
Chromosome
Supercoils
Coils
Nucleosome
Histones
DNA
double
helix
Section 12-2
B. DNA Replication
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
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
replication
template
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
Growth
Growth
Replication fork
DNA polymerase
New strand
Original strand DNA
polymerase
Nitrogenous bases
Replication fork
Original strand
New strand
III. RNA & Protein Synthesis
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:
1--Sugar is _________________ 2---Generally single-stranded 3---RNA contains ________________(U) in
place of thymine (T)
genes
uracil ribose
B. Types of RNA
Main job=_________________-ie the assembly of amino acids into proteins
3 Types: ____________________(mRNA)-carry copies for
instructions from DNA to rest of cell ____________________(rRNA)-type of RNA that helps
make up ribosomes,where proteins assembled ________________(tRNA)transfers each amino acid to
the ribosome as it is coded for on mRNA.
Protein synthesis
messenger
ribosomal Transfer
from to to make up
Concept MapSection 12-3
also called which functions to
also called also called which functions to
which functions to
can be
RNA
Messenger RNA Ribosomal RNA Transfer RNA
mRNA Carry instructions rRNACombine
with proteins tRNABring
amino acids toribosome
DNA Ribosome Ribosomes
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
RNADNA
RNApolymerase
Figure 12–14 TranscriptionSection 12-3
Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)
D. RNA editing
________________________ in eukaryotic genes ,sequences of nucleotides that ARE NOT involved in coding for proteins
_______________________-DNA sequence that does code for protein
introns
exons
E. Genetic Code
______________________-chain of amino acids=proteins
_________________-3 consecutive nucleotides that specify a specific amino acid
Example –UCGCACGGU reads UCG_CAC_GGU and codes for Serine-Histidine-Glycine
polypeptide
codon
The Genetic Code
Section 12-3
Universal code64 possible 3 base codonsAUG can specify methionine or start
codon3 stop codons that do not code for an
amino acid
F. Translation ______________________reads the instructions for
the order in which amino acids should be joined by reading mRNA
____________________________is the decoding of an mRNA message into a polypeptide(protein)
Before translation occurs,mRNA is transcribed from DNA and released into __________________________.
Translation begins when mRNA molecule in cytoplasm attaches to a _____________________.
ribosome
translation
cytoplasm
ribosome
As each codon of the mRNA moves through the moves through the ribosome,_____________brings in the proper,indicated amino acid and transferred to polypeptide chain
Each tRNA carries one kind of amino acid __________________ is a group of 3 bases on a
tRNA that are complementary to a mRNA codon Ribosome forms a _________________bond
between amino acids and breaks tRNA bond releasing it
Protein keeps growing until ribosome reaches stop codon on mRNA
tRNA
anticodonpeptide
Figure 12–18 TranslationSection 12-3
Figure 12–18 Translation (continued)Section 12-3
IV.Mutations=________________________
A.---Kinds of Mutations 1) ________________________________-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
Changes in genetic material
Point mutation
Frameshift mutation
Gene 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
duplication
inversions
translocations
Substitution InsertionDeletion
Gene Mutations: Substitution, Insertion, and Deletion
Section 12-4
Deletion
Duplication
Inversion
Translocation
Figure 12–20 Chromosomal Mutations
Section 12-4
B. Significance of Mutations
Many have no effect Harmful effects include genetic disorders and cancer ________________________-contains extra set of
chromosomes-bad in most cases but often helpful in PLANTS.
polyploidy
V. Gene Regulation
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
operon
operator
Regulatory sites
Promoter(RNA polymerase binding site)
Start transcription
DNA strand
Stop transcription
Typical Gene StructureSection 12-5
Karyotypes
top related