1. Biology 331 Genetics
Introduction

2. Genetics: The study of genes A gene is a particular bit of DNA
Deoxyribonucleic acid
Each gene codes for a particular character
The primary products of genes are proteins
Why are proteins important?
When you look at a cell what you see is either a protein or made by a protein...explain.

3. Genes are the agents of heredity:
Why dogs don't give birth to wildebeest?
Different genes yield a different product
But each dog is also different!
Alleles are different varieties of a gene
like eye color
Differences in alleles yield variation within a species

4. How does DNA do what it does?
Replication:
DNA must be able to copy itself
In most organisms this includes both Meiosis and Mitosis
Generation of form:
Something about DNA must let it act as a "blueprint" for life
Mutation:
DNA must be able to change over time
This is required for evolution

5. DNA Replication

6. Definitions: Genome: An organisms complement of DNA
Diploid: Carry two copies of each gene
Haploid: Carries one copy of each gene
Go over life history strategies
Chromosomes:
Units of DNA and protein which make up the genome
Homologous chromosomes:
Chromosomes in a diploid organism which contain copies of the same genes

7. Structure of DNA: A polymer of nucleotides
Composed of a phosphate group a nitrogenous base and a sugar
Differ by the base
Adenine(A)
Guanine (G)
Cytosine (C)
Thymine (T)

8. The Nucleotides

9. Bonding:
A chain of nucleotides is connected by phosphate groups and sugars
Connected by phosphodiester bonds
Always connect between the 3' and 5' carbons
Thus one end of the chain is a 5' phosphate group and the other is a 3' OH group
Has polarity

10. Two strands:
Two chains of nucleotides are bound to each other by hydrogen bonds
The chains are antiparallel (opposite directions)
Bonding between bases is specific
A-T
C-G
Bases which form pairs are complementary
The whole double strand is twisted in a double helix due to hydrophobic interactions

11. Double Helix

12. Double Helix #2

13. Making a copy: DNA must unwind
Exposed DNA can then act as a template for a copy
A new strand is catalyzed by DNA polymerase

14. Going the wrong way!
Copies 3’ to 5’ along the old strand

15. Generation of Form:
If DNA is a plan what is it a plan for?
Protein

16. Transcription: Making a working copy of the plan
The copy is made in RNA
Differs by its sugar from DNA
Contains Uracil (U) instead of thymine (T)
Production of the transcript is mediated by RNA polymerase
Moves down a transcription "bubble"
Goes from 5' to 3'

17. Transcription

18. Eukaryote Gene: Regulatory region: controls transcription
"stop" codon:
Coding region is interrupted by "Introns"
Introns are cut out
The remaining coding regions are Exons
mRNA (messenger RNA)
Composed of transcribed exons
mRNA moves to the cytoplasm
mRNA is read from 5' to 3'
Information is in triplet "codons"
Each codon equals an Amino Acid or a "stop" codon

19. Gene Structure

20. Protein synthesis: Ribosomes
Attach to 5' end and move along the DNA strand
Catalyzes formation of polypeptide strand
AAs brought to the polypeptide strand by tRNA (transfer RNA)
tRNA has a complimentary "anti-codon" to the mRNA codons
This puts AAs in order
RER -vs- "free" ribosomes

21. Translation

22. Making a protein

23. Genetic Variation: Due primarily to different alleles Genotype
varieties of genes
Genotype
Phenotype:
The character an organism possesses
Phenotype is ALWAYS a gene x environment interaction

24. Discontinuous variation:
Character is either present or absent
Often simpler to study
Polymorphisms:
different variant characteristics
"Morphs": Different varieties
"Wild type": A common morph
"Mutant": An uncommon morph

25. Morphs

26. Continuous variation:
Shows and unbroken range of phenotypes
Height, color etc.
Often has a normal distribution

27. Molecular basis for variation:
Modification of DNA code yields a modified protein
Substitution
Deletion
Insertion
Frameshift mutations
How does this affect the phenotype?
Enzyme structure
Induced fit hypothesis
Advantages of Diploidy
Being haplosufficient

28. Albinism

29. Genes and the environment:
Genotype -vs- Phenotype
The gene provides the plan
The environment provides the materials
In some cases it seems the gene is dominant and in others that the environment is dominant
Height in Japan
Twin studies
Sickle cell

30. Norm of reaction:
All of the possible phenotypes for a particular genotype
Tanning
Norms of reaction tend to overlap

31. Eye Size Norm of Reaction

32. Eye Norm of Reaction Continued

33. Achillea growth experiment
No "best" genotype for growth

34. Developmental noise:
An organisms final structure also depends upon developmental pathways
Fingerprints
Exact number of eye facets
Adds another random component