1. Single-Gene Inheritance Patterns
Chapter 2
1/26/17

2. Review Questions
In many species, there are two representatives of each chromosome. In such species, the characteristic number of chromosomes is called ___________. It is usually symbolized as ____________.
Haploid; n
Haploid; 2n
Diploid; n
Diploid; 2n

3. Review Question Genetics is the study of___________.
Heredity and variation
Mutation and recession
Transcription and translation
Variation of metagenomics analysis.

4. Chapter 2: Single Gene Inheritance
Wild type vs Mutants
Mutations arise heritable changes in the gene’s DNA
Genotypes vs Phenotypes
Polymorphisms
Coexistence of two or more common phenotypes of a biological property
Wild type is the most common form found in nature and heritable variations observed are mutants

5. Gene Discovery
4 Steps to Gene Discovery 1. Collect mutants affecting a biological property Genetic dissection and forward genetics 2. Cross the mutants to Wild type to see if their descendants show ratios of wild type to mutant that are characteristic of single-gene inheritance 3. Determine the gene function at the molecular level 4. Determine how the gene interacts with other genes to produce the biological property

6. The seven phenotypic pairs studied by Mendel
A a
R r
I i
Y y
L l or S s
P p
G g

8. Remember of Mendelian Genetics
© 2015 W. H. Freeman and Company

9. Complete 2 punnett squares starting with two pure peas, one with purple flowers peas and one with white flowers. Then self-cross for the F1 and F2. What are the three ratios of phenotype and genotype?

10. Quick concept check: What is Mendels 1st law?
Law of Segregation
What does this law state?
During the production of gametes the two copies of each hereditary factor segregate so that offspring acquire one factor from each parent

11. Introduce some terminology
Zygote
a fertilized egg, the first cell that develops into a progeny individual
Homozygous dominant, heterozygous, and homozygous recessive
AA, Aa, aa
Monohybrid
heterozygous for one gene is monohybrid
Monohybrid cross
Yy x Yy
Zygote- a fertilized egg, the first cell that develops into a progeny individual
Monohybrid – heterozygous for one gene is monohybrid

12. Mitosis Somatic cells Programmed stage
Any non-sex cell
Germ-line cells = Gametes = Sex cells
Programmed stage
One progenitor cell -> 2 genetically identical cells
2n  2 daughter cells that are both 2n
(Diploid cells)
2n  4n  2n
n  2n  n

13. Stages of the asexual cell cycle
M – Mitosis
G1 – Growth stage 1
S – DNA synthesis
G2 – Growth stage 2 M G2 G1
GROWTH 1 -growth -increase in size -new proteins and organelles made
Growth 2
preparation for cell division (lower Surface Area to V so the cell can become bigger) S
What is the difference between G1 and G2?

14. Meiosis Specialized diploid cells call meiocytes
(sex cells progenitors)
Two sequential cell divisions take place
Meiosis I and Meiosis II
2n (Diploid)  n + n + n + n (4 haploid cells)
2n  4n  2n + 2n  n + n + n + n

15. 3 cells of the meiotic tetrad abort in females
GP gametophyte
Female – mega gametophyte
Male – microgametophyte
Transient diploid cells only survive for a short time

16. Key stages of meiosis and mitosis

17. Pass Me A
Taco
Cytokinesis

19. More on Meiosis
Each meiotic division (both I and II) is formally divided into:
Prophase
Metaphase
Anaphase
Telophase
Prophase I is the most complex and lengthy
Made up of 5 parts

20. Stages of Meiosis

21. Stages of Meiosis

22. Stages of Meiosis

23. Stages of Meiosis

24. Stages of Meiosis
Linda zipped ping-pongs down Delaware

25. Mitosis and Meiosis Anyone confused on the steps still? IPMATC LZPDD
Quick Review
What are the stages of Mitosis?
What are the 5 stages of Prophase in Meiosis?

26. Mitosis takes place in haploid cells only. diploid cells only.
haploid or diploid cells.
bacterial cells only.

27. Meiosis takes place in haploid cells only. diploid cells only.
haploid or diploid cells.
somatic cells.

28. During meiosis I
homologous chromosomes align and are joined to one another (during synapsis).
homologous chromosomes align individually at the “equatorial plane,” similar to what occurs during mitosis.
homologous chromosomes align and are held together only at their centromeres.
sister chromatids separate and are drawn to opposite ends of a cell.

29. Good morning my fellow geneticists. This is Lecture for January 26th
Good morning my fellow geneticists. This is Lecture for January 26th. I have broken lecture into three parts today to allow you and myself to take breaks between the concepts we are going to cover today. To start off with we are going to discuss single gene inheritance in haploids. We covered single gene inheritance of diploids on Thursday.

34. Nuclear division at the DNA level
PART 2

35. Molecular Basis for Mendelian Inheritance Patterns
What causes different alleles?

36. PKU: Case Study Phenylketonuria disease
Phenylalanine tyrosine Phenylalanine
Hydroxylase (PAH)
Phenylalanine tyrosine
Phenylpyruvic acid
Phenylpyruvic acid interferes with the development of the nervous system, leading the mental retardation.
Babies tested at birth, if the deficiency is detect, phenylalanine is withheld from the diet

38. Mutant sites in the PKU gene
Mutations in black are in exons (expressed)
Mutations in green are in introns(interrupt)
Most are null mutations – make a non-functioning protein (typically a truncated protein)
Others are leaky mutations – makes a functional protein but it lacks the full function of the wt gene