1. Chapter 5 Lesson 3
DNA and Genetics

3. The Discovery of the Structure of DNA
James Watson and Fransis Crick
Rosalind Franklin

4. DNA Structure
DNA looks like a twisted ladder and is often called a ________________.
double helix

5. DNA Structure
The sides of the ladder are made up of molecules of ______________ called ______________ that are alternating with molecules of phosphate.
sugar
deoxyribose

6. DNA Structure
Ladder rungs are made up of a pair of molecules called nitrogen bases (containing nitrogen and other elements). The four nitrogen bases are:
____________________(A)
____________________(T)
____________________(G)
____________________(C)
Adenine
Thymine
Guanine
Cytosine

7. DNA Structure
How do the nitrogen bases pair up to make the rungs of the DNA ladder?
______________ pairs only with _______________
Adenine
Thymine
Cytosine
Guanine

8. Nitrogen Base Pairing

9. What is DNA Replication?
The process of copying a DNA molecule to make another DNA molecule that is an exact copy.

10. DNA Replication
DNA molecule unwinds and separates between the nitrogen bases on each rung.
____________________ that are floating in the nucleus pair up with each half (A with T and G with C)
Two identical DNA molecules are formed
The order of nitrogen bases in each new DNA molecule will exactly match the order in the original DNA molecule.
Nucleotides

11. DNA Replication DNA replication ensures that:
each new daughter cell will have a complete set of DNA which it needs to carry out all the cell’s activities.

12. DNA Replication

13. Let’s Review DNA
What are the 4 different nitrogen bases in a DNA molecule? How do they pair?
Adenine pairs with Thymine
Cytosine pairs with Guanine

14. Base Pairing – The secret to the code!!
Adenine pairs with Thymine
Guanine pairs with Cytosine

15. Introducing a New Player
This structure, along with DNA, is critical in the construction of YOU!
This structure comes in three different forms with different functions.
What is the name of this “New Player”?
RNA

16. DNA vs. RNA – How are they different?

17. DNA vs. mRNA How many strands in each? (ex. How many sides?)
DNA – Double strand
RNA – Single strand

18. DNA vs. mRNA What are the nitrogen bases in each? DNA – has A, T, C, G
RNA – has A, U, C, G

19. DNA vs. mRNA What is the sugar in each backbone? DNA – has deoxyribose
RNA – has ribose

20. Three types of RNA mRNA (messenger RNA) tRNA (transfer RNA)
rRNA (ribosomal RNA)

21. The Genetic Code
ATTCGGTG
Genes make proteins
Proteins make YOU!!

22. Protein Structure
unwind
Your DNA determines the proteins that are produced. These proteins give you your traits such as hair color, eye color, and skin color.

23. The Genetic Code (cont.)
What are the building blocks of protein?
A group of three nitrogen bases codes for a specific amino acid.
The production of proteins is called protein synthesis.
Two steps – Transcription and Translation

24. The Genetic Code
The order of nitrogen bases along a gene forms a Genetic Code that specifies what type of protein will be produced.
The type of protein produced determines the trait!
Are you ready to see the code that unlocks the mystery of life????
Are you sure?????
Are you really sure????

25. The Genetic Code

26. Protein synthesis takes place on the ribosome.

27. Two types of RNA

28. A Look at Protein Synthesis:

29. Protein Synthesis

30. Steps of Protein Synthesis Fig. 15 – pg. 173
DNA “unzips” between the Nitrogen Base pairs
mRNA nucleotides pair up with DNA nucleotides
Completed mRNA moves into the cytoplasm
This process is called TRANSCRIPTION

31. Steps of Protein Synthesis (cont.) Fig. 15 – pg. 173
The genetic messenger is called messenger RNA (or mRNA).
mRNA carries the DNA code from the nucleus out into the cell’s cytoplasm to the ribosomes where proteins are produced.
Why can’t DNA deliver the code to the ribosomes?
DNA is too large to fit through the nuclear pores.

32. Steps of Protein Synthesis (cont.) Fig. 16 – pg. 174
Transfer RNA (tRNA) carries amino acids to the ribosome.
tRNA matches up to mRNA using base pairing rules: A-U and C-G
Each tRNA molecule attaches the amino acid to the growing protein chain.
This process is called TRANSLATION (nucleic acid language is “translated” to amino acid language – a protein is made from mRNA)

33. A review of your notes: What is a codon? How many codons are possible?
Series of three nitrogen bases on mRNA
How many codons are possible?
64 codons
How many different amino acids are there?
20 different amino acids to form proteins

34. Let’s Review Protein Synthesis:

35. Mutation
Definition – a change in the nucleotide sequence of a gene. This causes the cell to produce an incorrect protein which results in a different physical trait or phenotype.

36. Mutations (pg. 175, Figure 17) Substitution Mutation Deletion Mutation
The mice ran away.
Substitution Mutation
The rice ran away.
Deletion Mutation
Thei cera naway.
Insertion Mutation
The migukce ran away.

37. Mutations Mutations are usually random and can be:
Harmful – causes harm to the organism
Helpful – helps the organism to survive
Neither harmful or helpful.
Mutations can also be caused by environmental hazards.
These are usually harmful

38. Cancer Cancer is a disease in which:
Cells grow and divide uncontrollably, damaging the parts of the body around them.
Cancer can occur when something damages a portion of DNA in a chromosome. This damage causes a change in DNA called _____________.
mutation

39. Cancer
Abnormal cells that develop uncontrollably may form a mass of abnormal cells which is called a _________________.
Treatment for cancer include _____________, ________________ and or ____________________
tumor
radiation
surgery
Drugs (chemotherapy)

40. Questions Why can’t DNA leave the nucleus to produce proteins?
Why is it important for meiosis to occur? What would happen if human sex cells had 46 chromosomes instead of 23?

41. Human Cells Human body cells contain 46 chromosomes (23 pairs)
Sex cells (egg and sperm) contain 23 chromosomes
The 23rd pair of chromosomes determines the sex of an individual.
Female genotype – XX
Male genotype – XY
Design a Punnett Square to calculate the probability of a man and woman having a baby girl of baby boy

42. Karyotype
Definition – picture of all the chromosomes in a cell arranged in pairs
Is this karyotype from a male or female?

43. Where is there a problem?