1. Unit 3 - Genetics & Biotechnology
Investigate how genetic information is stored, transmitted and expressed at the molecular level. (Chromosomes, Genes, DNA, RNA, Protein Synthesis, Biotechnology)
Investigate how genetic information is stored, transmitted and expressed at the chromosomal level. (Mitosis, Meiosis, Abnormal Meiosis/Genetic Defects)
Explore classical and current understandings of biological inheritance. (Mendelian Genetics, Monohybrid & Dihybrid Crosses)

3. Chromosomes, Genes & DNA

4. Genome
The nucleus of a human cell contains between 30,000 and 40,000 genes.
The complete set of genes is called a genome.
Structure of a genome:
Tightly coiled threads of DNA
Organized into structures called chromosomes.

5. Chromosomes A chromosome contains a single, long piece of DNA.
A chromosome is about 0.004mm long but contains a strand of DNA that is 4cm long. This means the DNA strand is about 10,000 times longer than the chromosome itself – thus the DNA has to be twisted and coiled in order to fit inside the chromosome.

6. Chromosomes
Humans have 23 pairs of chromosomes (46 chromosomes in total.)
Chromosomes are found in the nucleus of a cell. (Thus, there are 23 pairs of chromosomes in any one of the cells in your body!)
The DNA in each chromosome contains the code for about 2,000 genes.

7. Genes
A gene is a code made up of pairs of bases carried on the DNA molecule.
They are the basic physical and functional units of heredity.
Each DNA molecule contains many genes.

8. Genes Each gene is a specific sequence of bases.
These sequences carry the information needed for making proteins.
Recall: Proteins provide the structural components of cells and tissues as well as enzymes for essential biochemical reactions.
Remember: As seen on a previous slide, the complete set of genes is called a genome.

9. Genes
Of the 2,000 or so genes that each chromosome carries, most are common to all humans.
This means that 99.9% of your DNA is identical to all humans.
The remaining 0.1% influences the differences between us. For example, height, hair colour and susceptibility to a particular disease.
Environmental factors such as lifestyle (for example, smoking and nutrition) also influence the way we look and our susceptibility to disease.

11. Genes Video - https://www.youtube.com/watch?v=5MQdXjRPHmQ

12. DNA DNA stands for Deoxyribonucleic Acid.
It is the molecule that contains the genetic code.
The DNA molecule is made from two strands, twisted to form a double helix.
The double helix configuration of DNA was discovered in 1953 by James Watson and Francis Crick.

13. Double Helix Video https://www.youtube.com/watch?v=zwibgNGe4aY

14. Nucleotides/Bases DNA is a chain of nucleotides.
A nucleotide consists of a 5 carbon sugar (deoxyribose), a nitrogen-containing base attached to the sugar, and a phosphate group. There are four different types of nucleotides found in DNA, differing only in their nitrogenous bases.
When the nucleotides link together to form the DNA molecule, the sugar and phosphate form the molecule’s sugar-phosphate backbone.
Note: When referring to nucleotides, we call them by the same name as the base they contain.

15. Nucleotides/Bases Bases are nitrogen-containing chemicals.
On the DNA strand, they are paired up and form the “rungs” on the DNA “ladder”.
There are 4 bases:
adenine (A), thymine (T), guanine (G)
and cytosine (C)
Each base can only join with one other base.
- they join together in pairs (base pairs):
A with T, C with G

16. DNA Structure

17. Nucleotides/Bases Purines - Have 2) Pyrimidines
Nucleotides are divided into two groups:
Purines
- Have
two carbon
-nitrogen rings
2) Pyrimidines
- Have one carbon -nitrogen ring

18. Nucleotides/Bases
The particular order of nucleotides is called the DNA sequence.
The sequence gives the exact genetic instructions needed to create a particular organism with its own unique traits.

19. The Central Dogma
1. DNA is the genetic material containing genes responsible for physical traits observed in organisms.
2. DNA is replicated from existing DNA to produce new copies of the genome.
3. RNA is produced from DNA in a process called transcription
4. RNA is the message used to make proteins called translation.

20. DNA Replication For a cell to divide, it must first replicate its DNA.
DNA is replicated from existing DNA to produce new copies of the genome.

21. DNA Replication
First, an enzyme called helicase splits the DNA down the middle. Weak hydrogen bonds that hold the complementary nitrogen bases together are broken. The DNA now resembles a fork with two prongs (replication fork).
One strand is called the leading strand and the other is called the lagging strand.

22. DNA Replication
The two strands move apart and each parent strand acts as a template (pattern) to which free-floating nucleotides in a cell can attach to replace the missing half.
RNA primer (primase) attaches to the beginning of one of the strands (the lagging strand.) RNA primer attracts the free-floating nucleotides.
The nucleotides are attached at their complementary bases: adenine – thymine,
cytosine - guanine,
thymine – adenine,
guanine – cytosine.

23. DNA Replication
DNA polymerase attaches to the strands. The polymerase travels along each strand, adding nucleotides as it goes.
DNA polymerases are extremely accurate, making less than 1 error for every 10,000,000 nucleotides added.

24. Some polymerases can correct errors made during replication
Some polymerases can correct errors made during replication. When an incorrect base pair is recognized, the polymerase reverses its direction by one base pair. It then removes the incorrect base and replaces it with the correct one, then continues with replication. This is called proofreading.

25. DNA Replication
Each resulting DNA molecule has one old and one new strand. This is called semi-conservative replication because only the parent strands are conserved; the original, integrated molecule is not.

26. DNA Replication – Label Diagram

27. DNA Replication Video – https://www. youtube. com/watch
DNA Replication Video – DNA and Replication – Crash Course

28. Complete the DNA Structure Worksheet
Do DNA Extraction Lab & Complete Lab
questions.

29. Protein Synthesis – Quick Overview
Before cell division, the DNA in our chromosomes replicates so each daughter cell has an identical set of chromosomes.  In addition, the DNA is responsible for coding for all proteins
Each amino acid is designated by one or more set of triplet nucleotides. The code is produced from one strand of the DNA by a process called transcription. (Transcription occurs in the nucleus!)

30. Protein Synthesis – Quick Overview
This (making the protein from RNA, not transcription) can be done in the cytoplasm on clusters of ribosomes, called “polyribosomes” or it can be done on the membranes of the rough endoplasmic reticulum.

31. Transcription
Transcription converts a gene into a single-stranded RNA molecule.
RNA (Ribonucleic Acid) carries DNA’s instructions.
The central dogma states that information flows in one direction from DNA to RNA to proteins.

32. RNA RNA differs from DNA in three major ways: RNA has a ribose sugar.
RNA has uracil instead of thymine.
RNA is a single-stranded structure.

33. Transcription Transcription makes three kinds of RNA:
1) Messenger RNA (mRNA) carries the message that will be translated to form a protein.
2) Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made.
3)Transfer RNA (tRNA) brings amino acids from the cytoplasm to a ribosome.

34. Three Kinds of RNA

35. Transcription Transcription is catalyzed by RNA polymerase.
RNA polymerase and other proteins form a transcription complex.
The transcription complex recognizes the start of a gene and unwinds a segment of it.
start site
nucleotides
transcription complex

36. RNA polymerase moves along the DNA
Transcription
- Nucleotides pair with one strand of DNA.
RNA polymerase bonds the nucleotides together.
The DNA helix winds again as the gene is transcribed.
DNA
RNA polymerase moves along the DNA

37. Transcription
The RNA strand detaches from the DNA once the gene is transcribed.
RNA

38. Transcription

39. Transcription The transcription process is similar to replication.
Transcription and replication both involve complex enzymes and complementary base pairing.
The two processes have different end results.
Replication copies all the DNA; transcription copies a gene.
Replication makes one copy; transcription can make many copies.
growing RNA strands
DNA
one
gene

40. Translation Amino acids are coded by mRNA base sequences.
A codon is a sequence of three nucleotides that codes for an amino acid.
codon for
methionine (Met)
leucine (Leu)

41. Translation
Translation converts mRNA messages into polypeptides (chains of amino acids.)
It occurs in the cell’s cytoplasm, where the large and small subunits of the ribosomes are located.

42. Translation Ribosomes consist of two subunits:
The large subunit has three binding sites for tRNA.
The small subunit binds to mRNA.

43. Translation Amino acids are linked to become a protein.
An anticodon is a set of three nucleotides that is complementary to an mRNA codon.
An anticodon is carried by a tRNA.

44. Translation
A change in the order in which codons are read changes the resulting protein.
Regardless of the organism, codons code for the same amino acid.

45. Translation
The genetic code matches each codon to its amino acid or function.
three stop codons
one start codon, codes for methionine

46. The genetic code matches each RNA codon with its amino acid or function.

47. Translation
For translation to begin, tRNA binds to a start codon and signals the ribosome to assemble.
A complementary tRNA molecule binds to the exposed codon, bringing its amino acid close to the first amino acid.

48. Translation
The ribosome helps form a polypeptide bond between the amino acids.
The ribosome pulls the mRNA strand the length of one codon.

49. Translation The now empty tRNA molecule exits the ribosome.
A complementary tRNA molecule binds to the next exposed codon.
Once the stop codon is reached, the ribosome releases the protein and disassembles.

51. Summary of Protein Synthesis
Messenger RNA is made by a single strand of DNA in the nucleus. This is called transcription. The DNA code is passed to the messenger RNA.
Messenger RNA is carried from the nucleus, through the porous nuclear membrane, to the cytoplasm.
Messenger RNA travels to the ribosome.
Transfer RNA picks up amino acids in the cytoplasm, combines with them, and carries them to the ribosome.
Each transfer RNA lines up with its matching codon. Now the amino acids at the other end of the transfer RNA are in the right position to form a protein chain.
As the amino acids are lined up beside each other, they form bonds between them – forming a polypeptide chain or protein molecule.

52. Summary Function of DNA:
a) to replicate itself and pass code from one cell to daughter cells without change.
b) to function as a template for transferring code to mRNA.
2) Function of mRNA: to function as a template for translation of code into protein structure.
3) Function of protein:
a) structure of cells
b) as enzymes, they control all chemical activity of the cell.