1. Genetics
Chapter 13
Copyright © McGraw-Hill Companies Permission
Required for Reproduction or Display
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

2. Outline Genetics--> Definition Structure of DNA DNA Functions
Transcription
Translation
Mutation
Cytogenetics
Mendelian Genetics
Quantitative Traits
Linkage
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

3. Genetics can be defined as
The biological discipline involving the study of heredity
the study of genes.
the inheritance of physical traits.
the study and inheritance of DNA.
the study and inheritance of chromosomes
all of the above.
Focus on the MOLECULAR-->DNA (deoxyribonucleic acid)
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

4. 5-Carbon Sugar (Deoxyribose) Phosphate Group
Structure of DNA
DNA molecule organized into chain of nucleotides composed of three parts:
Nitrogenous Base
5-Carbon Sugar (Deoxyribose)
Phosphate Group
Nucleotides bonded to each other forming a helix.
Hydrogen bonds hold each base on one side of the helix to another base on the other side.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

5. Three Parts of DNA
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

6. Structure of DNA-->nucleotides
Four types of DNA nucleotides:
Purines--Adenine (A) and Guanine (G)
Pyrimidines--Cytosine (C) and Thymine (T)
Nitrogenous Base Part
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

7. Stern - Introductory Plant Biology: 9th Ed
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

8. Two chains binding together using hydrogen bonds
Helix structure:
Two chains binding together using hydrogen bonds
(base pairs)
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

9. Storage of Genetic Information
DNA Functions (ACGT)
Storage of Genetic Information
Gene - Segment of DNA that directs protein synthesis.
Protein may act as an enzyme influencing cell activities.
Genome - Sum total of DNA in an organism’s chromosomes.
Codon - Groups of three nucleotides.
(in a row, ex. AAT; AAA; GCT; etc…)
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

10. Replication of Information Occurs during S phase of cell cycle.
DNA Functions
Replication of Information
Occurs during S phase of cell cycle.
Strands of double helix unzip allowing DNA polymerase (enzyme) to pair individual nucleotides with the template strands.
Semi-Conservative Replication
Occurs simultaneously in both directions, and begins at several points simultaneously.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

11. DNA Replication
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

12. Expression of Information
DNA Functions
Expression of Information
Different subset of the genetic information is read in each cell type.
Expression requires two processes.
Transcription - Copy of gene message using RNA (intermediate nucleic acid).
Translation
Messenger RNA (mRNA) translated to produce proteins.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

13. Outline Genetics--> Definition Structure of DNA DNA Functions
Transcription
Translation
Mutation
Cytogenetics
Mendelian Genetics
Quantitative Traits
Linkage
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

14. Language metaphor Central Dogma of Molecular Biology
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

15. Three different types of RNA produced:
Transcription
Three different types of RNA produced:
Messenger RNA (mRNA)-->proteins
Transfer RNA (tRNA)-->translation
Ribosomal RNA (rRNA)
RNA Synthesis (ACGU nucleotide parts)
Nucleotides added to single stranded DNA molecule by RNA polymerase.
Only portions of the genome replicated.
Remainder is noncoding DNA (includes directions for expression!).
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

16. Stern - Introductory Plant Biology: 9th Ed
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

17. mRNA transcripts are decoded into proteins.
Translation
mRNA transcripts are decoded into proteins.
Genetic code based on codons.
64 possible combinations of ACGT/U) (43)
Code for 20 amino acids.
tRNA acts as a translator.
Anticodon binds to mRNA codon.
Ribosomal RNA (rRNA) binds to mRNA and facilitates translation
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

18. Genetic Code/ codons encode for 20 amino acids = proteins
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

19. Stern - Introductory Plant Biology: 9th Ed
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

20. Mutations - Changes in DNA sequence. Mutagens - Agents that alter DNA.
Ultraviolet light
Ionizing radiation (Pasta wheat/Ruby red)
Somatic Mutation - Occurs in body cell.
Germ-Line Mutation - Occurs in tissues that will produce sex cells.
Passed on to future generations.
All genetic variability due to mutations.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

21. Changes in Chromosome Structure
Cytogenetics
Cytogenetics is the study of chromosome behavior and structure, from a genetic point of view.
Changes in Chromosome Structure
Inversion - Chromosomal piece is broken and reinserted in the opposite orientation.
ABCDE ABDCE
Translocation - Chromosomal piece breaks off and attaches to another chromosome.
Important in speciation (rye)
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

22. Changes in Chromosome Number
Cytogenetics
Changes in Chromosome Number
Mistakes during chromosome pairing and separation can result in gametes carrying extra or missing chromosomes.
Aneuploid - Carries, or is missing, an extra chromosome(s).
Polyploid - Has at least one complete extra set of chromosomes.
Many cultivated plants are polyploid because they are bigger and produce more.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

23. Tetraploid Diploid S. tuberosum
Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

24. Genetics from Mendel to Today
Gregor Mendel (Austrian Monk) inheritance of traits ( ); rediscovered in 1900s
Used peas
Watson & Crick model of DNA (1954)
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

25. Crossed a tall plant with a short plant. Parental Generation (P)
Mendelian Genetics
Mendel crossed self-pollinated pea plants and recorded his observations.
Crossed a tall plant with a short plant.
Parental Generation (P)
All offspring were tall.
First Filial Generation (F1)
Cross offspring yielded a ratio of three tall individuals to one short individual.
Second Filial Generation (F2)
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

26. Stern - Introductory Plant Biology: 9th Ed
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

27. Mendelian Genetics Law of Unit Characters
Factors (Alleles), which always occur in pairs, control the inheritance of various characteristics.
Genes are always at the same position (locus) on homologous chromosomes.
Law of Dominance
For any given pair of alleles, one (Dominant) may mask the expression of the other (recessive).
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

28. Phenotype refers to an organism’s physical appearance.
Mendelian Genetics
Phenotype refers to an organism’s physical appearance.
Genotype refers to the genetic information responsible for contributing to the phenotype.
Homozygous - Both alleles identical.
Heterozygous - Alleles are contrasting.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

29. start
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

30. Monohybrid Cross (one trait)
A cross is made between two true-breeding parents differing for a single trait, producing an F1 generation. RR X rr
These plants are intercrossed to produce an F2 generation. R r R R RR Rr Rr Rr R r Rr rr Rr Rr r r
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

31. Mendelian Inheritance Pattern
The phenotype of the F1 resembled one parental form.
All F1s looked the same.
The “hidden” parental form reappeared in the F2 generation.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

32. Stern - Introductory Plant Biology: 9th Ed
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

33. Cross made for parents differing in two traits.
Dihybrid Cross
Cross made for parents differing in two traits.
Mendel’s Law of Independent Assortment
Factors (genes) controlling two or more traits segregate independently of each other.
Linked genes do not segregate independently.
Punnett Square used to determine genotypes of the zygotes.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

34. Dihybrid Cross Parents differing in 2 unlinked genetic traits
Green pod, Tall plant
(GGTT) X
yellow pod, dwarf plant
(ggtt)
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

35. A cross between a hybrid and one of its parents.
Mendelian Genetics
Backcross
A cross between a hybrid and one of its parents.
Can be used to test inheritance theory.
Incomplete Dominance
Some genes exhibit traits in which a heterozygote is intermediate in phenotype to the two homozygotes.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

36. Incomplete Dominance Camellias Snapdragons
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

37. Quantitative Traits
Quantitative traits exhibit a range of phenotypes rather than discrete phenotypes studied by Mendel.
Molecular geneticists are able to identify chromosomal fragments, quantitative trait loci, associated with quantitative traits.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

38. Inheritance of Corn height (Quantitative)
Cross Tall corn (6 m) x short corn (2 m)
F2 are not 3:1 tall to short but all heights between 1.5 m and 8 m P1 P2
# of plants
Plant height
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

39. Occurs with 2 traits - often located close together on chromosome
Linkage
Occurs with 2 traits - often located close together on chromosome
Often segregate like a single trait
No recombination occurs
Get a shortage of unique gamete genotypes in F1 generation
Get fewer genotypes in F2 generation
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

40. Stern - Introductory Plant Biology: 9th Ed
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

41. Genes that are together on a chromosome are said to be linked.
Linkage and Mapping
Genes that are together on a chromosome are said to be linked.
Each gene has a specific location (locus) on a chromosome.
Crossing-over should be more likely between two genes located far apart on a chromosome that between two genes located closer together.
Crossing over frequency can be used to construct a genetic map.
1 map unit = 1% crossing over.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

42. Review Structure of DNA DNA Functions Transcription Translation
Mutation
Cytogenetics
Mendelian Genetics
Quantitative Traits
Linkage
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

43. Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

44. Entranuclear DNA is found in both mitochondria and chloroplasts.
Extranuclear DNA
Entranuclear DNA is found in both mitochondria and chloroplasts.
Endosymbiont Hypothesis theorized mitochondria and chloroplasts were free-living, and at some point became incorporated into cells of organisms that evolved into plants and established a symbiotic relationship.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

45. Promoter Region signals transcription enzymes to attach to the DNA.
Single-stranded RNA transcript produced.
Chromosomes contain genes for building tRNA.
Each form of tRNA has a specific anticodon loop.
Base pairs with codon.
Genes for rRNA also transcribed in the nucleus - Used to construct ribosomes.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

46. Hardy-Weinberg Law
Hardy-Weinberg states the proportions of dominant alleles to recessive alleles in a normally interbreeding population will remain the same from generation to generation in the absence of external forces.
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

47. Central Dogma of Molecular Dogma
Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies