Training

1
Epistasis 2 sets of genes interact to produce one
phenotype
flower color in pea plants cc masks P- alleles C
has color P purple c no color (white) p
white Dihybrid cross
2
Complementation reveals whether 2 recessive
mutations are alleles of the same or different
genes
a1a1
a2a2
a1a1B3B3
A1A1b3b3
a1a2
A1a1B3b3
complementation seen 2 mutant alleles of
different genes
no complementation 2 mutant alleles of same gene
3
Complementation Test among 6 Mutant Strains of
Peas
Gene I alleles 1, 5 Gene II alleles 2, 4,
6 Gene III allele 3
4
GENETICS Ch 3
Chromosomal basis of heredity

• Topics
• Mitosis
• Meiosis
• Human sex linkage nondisjunction
• Chromosome structure

5
Mitosis vs. Meiosis

• Mitosis passes on genetic information
• - Asexual reproduction
• - Growth, healing maintenance
• - Clones of cells produced

• Meiosis creates new combinations of genes
• - Sexual reproduction
• - Basis of gamete and spore production
• - Produces genetic variation in organisms

6
Chromosome for Selected Species
7
Cell Cycle
Cytoplasm divides
Cell growth
DNA replication Chromosomes duplicate
cytokinesis
Cell prepares to divide
chromosome copies separate
8
Cell Cycle under Genetic Control
cyclin-CDK complexes kinases add P to
proteins Phosphatase reverses effects of CDKs
9
Mitosis
nucleus
cytoplasm
spindle pole
spindle equator
microtubules as a spindle apparatus
spindle pole
10
one chromosome (unduplicated)
one chromatid
its sister chromatid
one chromosome (duplicated)
ONE CHROMATID
CENTROMERE
ONE CHROMATID
11
CELL AT INTERPHASE
EARLY PROPHASE
LATE PROPHASE
PROMETAPHASE
chromosomes
nucleus
microtubules
pair of centrioles
nuclear envelope
plasma membrane
12
Spindle Attachment at Kinetochore
13
METAPHASE
ANAPHASE
TELOPHASE
INTERPHASE
14
Mitosis
Click to view animation.
15
Mitosis Review
16
Animal Cell Cytokinesis
Microfilaments contract
Cleavage furrow
17
Plant Cell Cytokinesis
cell wall
former spindle equator
cell plate
vesicles converging
18
(interphase) DNA replication
MITOSIS
prophase
Whats missing?
telophase
metaphase
anaphase
19
Sexual Reproduction

• Involves 2 parents
• Each parent passes on a single set of
  chromosomes to offspring
• Chromosome must be maintained in the new
  offspring

1 2 3 4 5 6
7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 XX (or XY)
human karyotype with homologous pairing