1. Chapter 12 How Genes Work

2. Cooperative Activity 1. What do you know about DNA?
2. What do you want to know about DNA?

3. DNA & Today 1988: DNA profiling was used in Britain, murder of 2 girls
1994: OJ Simpson murder trial
Crime shows
Cold Cases

4. Review: What is DNA? DNA stores our genetic information
Where is DNA found?
Nucleus of cell

5. What is a gene? Section of DNA that codes for a trait
Where are genes found?
Chromosomes

6. What is a chromosome? Bundles of DNA Where are chromosomes found?
Nucleus of cell

7. What do these words have in common?
DNA
Chromosomes
Genes

9. Introduction Humans are made up of: 20,000 – 30,000 genes
23 pairs of chromosomes
3 billion nitrogen bases

10. Human Genome Genetic map of the human body
Includes chromosomes and genes

11. Human Genome (cont.)
You inherit 2 copies of every gene
one from mom & one from dad

12. Human Genome (cont.)
Only 1% of your DNA codes for genes

13. Human Genome (cont.)

14. Why are genes important?
Genes contain the instructions to make proteins

15. Structure of DNA Made up of parts: nucleotides
Chemical building blocks

16. Parts of a Nucleotide Nitrogen-containing Base (A, T, C, G)
Sugar (Deoxyribose)
Phosphate
Group

18. Base Pairing Adenine (A) & Thymine (T) Cytosine (C) & Guanine (G)
Hydrogen bonds hold bases together

19. Base Pairing

20. DNA – Basic Structure Backbone: Alternating Sugar & Phosphate
Inside: Nitrogen Bases
Shape: Double Helix

21. Structure of DNA

22. Making Copies of DNA
Every time our body makes new cells, we need more DNA
This process is called: DNA Replication

23. DNA Replication – Step 1
Helicase (enzyme)
unwinds chains
separates nucleotides by breaking bonds

24. DNA Replication – Step 2
2. DNA polymerase assembles new chains
Complementary to one another

25. DNA Replication – Step 3
3. DNA ligase links the two sections

26. DNA Replication – End Result
Two identical strands of DNA (Two daughter DNA)

27. Reading the Genetic Code
Genes have the instructions to make proteins
Occurs in two steps
Transcription
Translation

28. Review: Protein Synthesis
Q: Which organelle helps make proteins?
Ans: Ribosomes

29. Transcription
Process of copying genetic information from DNA to mRNA (messenger)
Takes place in nucleus

30. Carries copied info from nucleus to ribosomes
Why do we need mRNA?
Carries copied info from nucleus to ribosomes
DNA cannot leave the nucleus
Protect the code

31. 1. Unwinds DNA double helix
Transcription Steps
RNA Polymerase
1. Unwinds DNA double helix
2. Adds RNA nucleotides to build mRNA chain

32. Transcription Steps (cont.)
3. mRNA moves out of nucleus

33. Transcription Animation

35. Translation
Process of assembling amino acids into proteins on ribosomes
Order of amino acid determines protein

36. Translation Steps tRNA (transfer)
1.) 3 letter code on tRNA anticodon matches up with mRNA codon
tRNA (transfer)

37. Translation Steps (cont)
2.) tRNA interprets the mRNA code sequence
3.) Code is read 3 letters at a time

38. Translation Steps (cont)
4.) Amino acids bond together to form proteins

39. Mutations A change in the copying of the genetic message
Can occur during DNA replication or transcription
Rare - occur in 1 out of 1 billion bases

40. Factors that affect the rate of mutations
Mutagens
Radiation / UV light
Chemicals

41. Translating The Code Example tRNA anticodon: AAA mRNA codon: UUU
UUU codes for amino acid phenylalanine

42. Translation
mRNA
tRNA

44. Translation

45. Codon (mRNA) Table

46. RNA DNA Venn Diagram: RNA & DNA ribonucleic acid
Structure
A – U (Uracil)
C – G
Single stranded
DNA
deoxyribo- nucleic acid
Structure
A – T
C – G
Double stranded

47. MCAS Questions Which of the following statements best describes
why the change in only one DNA base of the
hemoglobin 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.

48. MCAS Questions In a eukaryotic cell, which of the
following processes directly
involves DNA?
A. translation 
B. cellular respiration 
C. active transport of ions
D. replication of chromosomes

49. MCAS Questions 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.

50. MCAS Questions During DNA replication, the wrong
nucleotide was inserted in the DNA
sequence. Which of the following
terms describes this situation?
A. mutation  C. transcription
B. regeneration   D. translation

51. MCAS Questions A portion of one strand of a DNA molecule
has the sequence shown below ACCTGAAGG
Assuming there are no mutations in this
portion of the DNA, what is the corresponding
sequence on the complementary DNA
strand?
A.ACCTGAAGG  C.TGGACTTCC 
B.GTTCAGGAA  D.UGGACUUCC

52. MCAS Questions Fireflies 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.

53. MCAS Questions Individuals with one form of lactose
intolerance do not produce the enzyme
lactase because the gene coding for
the production of lactase is shut off in
their cells. This means that which of the
following processes does not occur for
the gene?
A. Hydrogenation C. replication
B.mutation  D. transcription

54. 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.