chapter 12 how genes work
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Chapter 12 How Genes Work. Cooperative Activity. 1. What do you know about DNA? 2. What do you want to know about DNA?. DNA & Today. 1988: DNA profiling was used in Britain, murder of 2 girls 1994: OJ Simpson murder trial Crime shows Cold Cases. Review: What is DNA?. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 12 How Genes Work
Cooperative Activity
1. What do you know about DNA?
2. What do you want to know about DNA?
DNA & Today
1988: DNA profiling was used in Britain, murder of 2 girls
1994: OJ Simpson murder trial
Crime showsCold Cases
Review: What is DNA?
DNA stores our genetic information
Where is DNA found? Nucleus of cell
What is a gene?
Section of DNA that codes for a trait
Where are genes found? Chromosomes
What is a chromosome?
Bundles of DNA Where are chromosomes
found? Nucleus of cell
What do these words have in common?
DNAChromosomesGenes
IntroductionHumans are made up of:
20,000 – 30,000 genes
23 pairs of chromosomes
3 billion nitrogen bases
Human Genome
Genetic map of the human body
Includes chromosomes and genes
You inherit 2 copies of every gene one from mom & one from dad
Human Genome (cont.)
Only 1% of your DNA codes for genes
Human Genome (cont.)
Human Genome
(cont.)
Why are genes important? Genes contain the
instructions to make proteins
Structure of DNA
Made up of parts: nucleotides
Chemical building blocks
Parts of a Nucleotide
Nitrogen-containing Base (A, T, C, G)
Sugar (Deoxyribose) Phosphate
Group
Base Pairing
Adenine (A) & Thymine (T)Cytosine (C) & Guanine (G)
Hydrogen bonds hold bases together
Base Pairing
DNA – Basic Structure
Backbone: Alternating Sugar & Phosphate
Inside: Nitrogen BasesShape: Double Helix
Structure of DNA
Making Copies of DNA
Every time our body makes new cells, we need more DNA
This process is called: DNA Replication
DNA Replication – Step 1
Helicase (enzyme) unwinds chains separates
nucleotides by breaking bonds
2. DNA polymerase assembles new chains
Complementary to one another
DNA Replication – Step 2
3. DNA ligase links the two sections
DNA Replication – Step 3
Two identical strands of DNA (Two daughter DNA)
DNA Replication – End Result
Reading the Genetic Code Genes have the instructions
to make proteinsOccurs in two steps
TranscriptionTranslation
Review: Protein SynthesisQ: Which organelle helps
make proteins?Ans: Ribosomes
Transcription Process of copying
genetic information from DNA to mRNA (messenger) Takes place in nucleus
Why do we need mRNA?
Carries copied info from nucleus to ribosomes
DNA cannot leave the nucleus Protect the code
Transcription Steps
RNA Polymerase1. Unwinds DNA double
helix2. Adds RNA nucleotides
to build mRNA chain
Transcription Steps (cont.)
3. mRNA moves out of nucleus
Transcription Animation
Translation Process of assembling
amino acids into proteins on ribosomes
Order of amino acid determines protein
Translation Steps
1.) 3 letter code on tRNA anticodon matches up with mRNA codon
tRNA (transfer)
Translation Steps (cont)
2.) tRNA interprets the mRNA code sequence
3.) Code is read 3 letters at a time
Translation Steps (cont)
4.) Amino acids bond together to form proteins
MutationsA change in the copying of
the genetic messageCan occur during DNA
replication or transcriptionRare - occur in 1 out of 1
billion bases
Factors that affect the rate of mutationsMutagens
Radiation / UV light
Chemicals
Translating The Code
Example tRNA anticodon: AAA mRNA codon: UUU
UUU codes for amino acid phenylalanine
Translation
tRNA
mRNA
Translation
Codon (mRNA) Table
Venn Diagram: RNA & DNARNA ribonucleic
acid Structure
A – U (Uracil)C – G
Single stranded
DNA deoxyribo-
nucleic acid Structure
A – T C – G
Double stranded
MCAS QuestionsWhich of the following statements best describeswhy the change in only one DNA base of thehemoglobin gene results in a different protein product of the gene?A. The change prevents mRNA from being made. B. The change alters the amino acid sequence of
the protein. C. The change causes the blood cells to divide in
an uncontrolled way. D. The change creates a second strand of mRNA
for each RNA molecule.
MCAS QuestionsIn a eukaryotic cell, which of the following processes directly involves DNA?A. translation B. cellular respiration C. active transport of ionsD. replication of chromosomes
In a molecule of double-stranded
DNA, the amount of adenine
present is always equal to the
amount of
A. cytosine. C. thymine.
B. guanine. D. uracil.
MCAS Questions
MCAS QuestionsDuring DNA replication, the wrong nucleotide was inserted in the DNA sequence. Which of the following terms describes this situation? A. mutation C. transcriptionB. regeneration D. translation
MCAS QuestionsA portion of one strand of a DNA moleculehas the sequence shown below.
ACCTGAAGGAssuming there are no mutations in thisportion of the DNA, what is the correspondingsequence on the complementary DNAstrand? A.ACCTGAAGG C.TGGACTTCC B.GTTCAGGAA D.UGGACUUCC
MCAS QuestionsFireflies produce light inside their bodies. The enzyme luciferase is involved in the reaction that produces the light. Scientists have isolated the luciferase gene.
A scientist inserts the luciferase gene into the DNA of cells from another organism. If these cells produce light, the scientist knows that which of the following occurred?
A. The luciferase gene mutated inside the cells. B. The luciferase gene was transcribed and translated. C. The luciferase gene destroyed the original genes of the
cells. D. The luciferase gene moved from the nucleus to the
endoplasmic reticulum.
MCAS QuestionsIndividuals with one form of lactoseintolerance do not produce the enzymelactase because the gene coding forthe production of lactase is shut off intheir cells. This means that which of thefollowing processes does not occur forthe gene?A. Hydrogenation C. replicationB.mutation D. transcription
MCAS Questions
Which of the following statements best describes a DNA molecule?
A. It is a double helix.
B. It contains the sugar ribose.
C. It is composed of amino acids.
D. It contains the nitrogenous base uracil.