1. Chapter 12: Cell Division, Modes of Inheritance
BIOL 2416
Chapter 12: Cell Division, Modes of Inheritance
Chapter 11: Mendel’s Laws, Punnett Squares, Branch Diagrams, Chi Square Test

3. Fig. 1.22 Comparison of mitosis and meiosis in a diploid cell
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

4. Fig. 1.22 Comparison of mitosis and meiosis in a diploid cell (continued)
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

5. Glossary P = parental generation F1 = 1st filial generation (kids)
F2 = 2nd filial generation (grandkids)
Self cross = selfing = self-fertilization e.g. F1 X F1 to produce F2
Back cross = F1 x P

6. Glossary, cont’d: Character = heritable feature (e.g. eye color)
Trait = specific version of a character (e.g. BLUE eye color)
Gene = discrete unit of hereditary information = meaningful chunk of DNA that is transcribed into (m)RNA and may result in protein (e.g. the gene for eye color pigment)
Allele = specific version of a gene (e.g. blue eye color allele, or brown eye color allele)
Locus = specific location of gene on chromosome

7. Glossary, cont’d: Truebreeding = inbred to the point of homozygosity
Homozygous individual = homozygote = has 2 identical alleles for a given gene (e.g. BB or bb)
Heterozygous individual = heterozygote = has 2 different alleles for a given gene (e.g. Bb)
Dominant allele = fully expressed in heterozygote (e.g. B)
Recessive allele = masked in heterozygote (e.g. b)

8. Glossary, cont’d:
GENotype = GENetic makeup of an individual (e.g. BB, Bb, or bb)
PHenotype = PHysical characteristic of an individual (e.g. brown eyes or blue eyes); may be visible or measurable (biochemical) characteristic, or may refer to disease status.

9. Get in the habit…

10. Genotypes (help) lead to phenotypes:
POSSIBLE GENOTYPES
POSSIBLE PHENOTYPES BB
brown eyes Bb bb
blue eyes

11. More Glossary: Monohybrid cross
= strictly speaking, a cross between 2 individuals that are heterozygous at 1 gene: Aa x Aa
Dihybrid cross
= strictly speaking, a cross between 2 individuals that are heterozygous at 2 genes: AaBb x AaBb

12. Even More Glossary: Reciprocal matings
Male with 1st trait x female with 2nd trait
Female with 1st trait x male with 2nd trait
Test cross
Individual with dominant phenotype and unknown genotype (AA or Aa?) x homozygous recessive (aa)
F1 phenotypic ratios determine whether unknown genotype is AA or Aa

13. It is not possible to predict the genotype of an organism with a dominant phenotype.
The organism must have one dominant allele, but it could be homozygous dominant or heterozygous.
A test cross, breeding a homozygous recessive with dominant phenotype, but unknown geneotype, can determine the identity of the unknown allele.
Fig. 14.6
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14. Probability Review Scale = 0 to1 (fractions or percentages)
Random events occur independently of one another (separate coin tosses)
Rule of Multiplication
Keyword “ AND”
Probability that 2 events occur simultaneously is product of individual probabilities
Rule of Addition
Keyword “ OR”
If 2 or more independent (mutually exclusive) ways lead to Rome, add them up

15. Fig. 10.4 Seven character pairs in the garden pea that Mendel studied in his breeding experiments
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

16. Gregor Mendel’s Particulate Theory of Inheritance
Law of Segregation
2 alleles for a gene are packaged into separate gametes (so each gamete has ONE allele per gene)
Alleles get back together after fertilization (fusion of 1 sperm + 1 egg)
Law of Independent Assortment
Genes on different chromosomes are transmitted independently of one another

17. Fig. 10.6 The F2 progeny of the cross shown in Figure 10.5
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

18. Fig. 10.8a Mendel’s first law, principle of segregation of Mendelian factors: Production of the F1 generation
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

19. Fig. 10.8b Mendel’s first law, principle of segregation of Mendelian factors: Production of the F2 generation
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

20. Fig Using the branch diagram approach to calculate the ratios of phenotypes in the F2 generation of the cross in Figure 10.8
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

21. Table 14.1
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

22. Law of Independent Segregation: SSYY x ssyy
Find genotypic ratios and phenotypic ratios in the F1 by
Punnett square method
Branch diagram method

23. Now self-cross the F1: SsYy x SsYy
Find genotypic and phenotypic ratios in the F2 by
Punnett square method
Branch diagram method

24. Fig. 10.12b Derivation of F2 genotypes and 9:3:3:1 phenotypic ratio by use of the Punnett square
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

25. Fig Using the branch diagram approach to calculate the F2 phenotypic ratio of the cross in Figure 10.12
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

26. Some Useful Numbers # of possible combinations = (# of positions)
(# of choices per position)

27. (max) # phenotypic classes (max) # genotypic classes
Ss x Ss
SsYy x SsYy
SsYyCc x SsYyCc
(max) # gametes
21 = 2
22 = 4
23 = 8
(max) # phenotypic classes
(max) # genotypic classes
31 = 3
32 = 9
33 = 27

28. Chi Square Test
Quantifies the difference between OBSERVED and EXPECTED results
Determines the likelyhood that this discrepancy is due to chance
Chance is GOOD
If the discrepancy is NOT due to chance, the “null hypothesis” must be REJECTED

29. How to Find Chi-square Value
C1: List expected phenotypic classes
C2: List observed numbers (o) for each class
Total
C3: using the expected phenotypic ratio and the total actual offspring, calculate expected numbers (e)
C4: for each row, calculate d = o - e
C5: for each row, calculate d2
C6: for each row, calculate d2/e
Total all values in C6 to find 2 value

30. Chi-Square COIN TOSS C1 C2 C3 C4 C5 C6 Pheno classes o e d = o - e d2
d2 / e
Heads
Tails
Total
100
2 =

31. Chi Square Probabilities
Determine degrees of freedom = df = # of phenotypic classes - 1
In correct df row (see Table 11.5, pg.313), find your 2 value
Move up the table to find P value
If P > 0.05, the null hypothesis stands

32. Table 3-1

33. Fig. 10.16 Symbols used in human pedigree analysis
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

34. Clues
Autosomal = equal opportunity disorder (normal carriers possible)
X-linked = affects males > females, if recessive (most common)
Dominant = once it’s gone, it’s GONE
Recessive = can skip a generation (come out of “nowhere”)

35. Inheritance Patterns Autosomal recessive Autosomal dominant
(se)X-linked recessive
(se)X-linked dominant
(Y-linked)
(see handout on pedigree problem strategies)

36. Fig. 10.17 Example of a human pedigree
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

37. Fig b Part of a pedigree showing the transmission of the autosomal dominant trait of woolly hair
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

38. Human Disorder Resources

39. Autosomal recessive Autosomal dominant Albinism Cystic fibrosis
Tay-Sachs disease
Sickle cell anemia
alkaptonuria
Autosomal dominant
Woolly hair
Achondroplasia
Brachydactyly
Marfan syndrome
Huntington’s disease

40. X-linked recessive X-linked dominant Hemophilia Color blindness
Duchenne’s muscular dystrophy
Lesh-Nyhan syndrome
X-linked dominant
Faulty tooth enamel

41. Tests are also available to determine in utero if a child has a particular disorder.
One technique, amniocentesis, can be used beginning at the 14th to 16th week of pregnancy to assess the presence of a specific disease.
Fetal cells extracted from amniotic fluid are cultured and karyotyped to identify some disorders.
Other disorders can be identified from chemicals in the amniotic fluids.
Fig a
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

42. A second technique, chorionic villus sampling (CVS) can allow faster karyotyping and can be performed as early as the eighth to tenth week of pregnancy.
This technique extracts a sample of fetal tissue from the chorionic villi of the placenta.
This technique is not suitable for tests requiring amniotic fluid.
Fig b
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings