Genetics review

Chapters 12-15

Mitosis

• Why mitosis?• Homologous chromosomes• Chromatids• Haploid• Diploid• Binary fission• Tumor• Metastasis

Fig. 12-40.5 µm Chromosomes

Chromosomeduplication(including DNAsynthesis)

Chromo-some arm

Centromere

Sisterchromatids

DNA molecules

Separation ofsister chromatids

Centromere

Sister chromatids

Fig. 12-5

S(DNA synthesis)

MITOTIC(M) PHASE

Mito

sis

Cytokinesis

G1

G2

Fig. 12-17b

Cyclin isdegraded

Cdk

MPF

Cdk

MS

G 1G2

checkpoint

Degradedcyclin

Cyclin

(b) Molecular mechanisms that help regulate the cell cycle

G2

Cyclin

accum

ulatio

n

Meiosis

• Genetic variation• Chiasmata• Synapsis

Mendel genetics

• Homozygous• Heterozygous• Parental, F1, F2

• Genotype• Phenotype• Testcross• Monohybrid• Dihybrid

Mendel

• Law of segregation• Law of independent assortment• Incomplete dominance• Codominance• Multiple alleles• Epistasis• Pleiotropy • Polygenes • Dominant disorders

Fig. 14-14

Fig. 15-2P Generation Yellow-round

seeds (YYRR)

Y

F1 Generation

Y

R R

R Y

r

r

r

y

y

y

Meiosis

Fertilization

Gametes

Green-wrinkledseeds ( yyrr)

All F1 plants produceyellow-round seeds (YyRr)

R R

YY

r ry y

Meiosis

R R

Y Y

r r

y y

Metaphase I

Y Y

R Rrr

y y

Anaphase I

r r

y Y

Metaphase IIR

Y

R

y

yyy

RR

YY

rrrr

yYY

R R

yRYryrYR1/41/4

1/41/4

F2 Generation

Gametes

An F1 F1 cross-fertilization

9 : 3 : 3 : 1

LAW OF INDEPENDENTASSORTMENT Alleles of geneson nonhomologouschromosomes assortindependently during gameteformation.

LAW OF SEGREGATIONThe two alleles for each geneseparate during gameteformation.

1

2

33

2

1

Wild type (w+)

http://upload.wikimedia.org/wikipedia/commons/9/94/EyeColors.jpg

Sex linked

• Hemophilia• Color blindness• Duchene’s muscular dystrophy

Fig. 15-4

PGeneration

Generation

Generation

Generation

Generation

Generation

F1

F2

All offspring had red eyes

Sperm

EggsF1

F2

P

Sperm

Eggs

XX

XY

CONCLUSION

EXPERIMENT

RESULTS

w

w

w

w

ww

w w

+

+

++ +

w

ww w

w

w

w

ww

+

+

+

+ +

+

Linked genes

• Genes on same chromosome• Testcross more parental types

Fig. 15-10Testcrossparents

Replicationof chromo-somes

Gray body, normal wings(F1 dihybrid)

Black body, vestigial wings(double mutant)

Replicationof chromo-somes

b+ vg+

b+ vg+

b+ vg+

b vg

b vg

b vg

b vg

b vg

b vg

b vgb vg

b vg

b+ vg+

b+ vg

b vg+

b vg

Recombinantchromosomes

Meiosis I and II

Meiosis I

Meiosis II

b vg+b+ vgb vgb+ vg+

Eggs

Testcrossoffspring

965Wild type

(gray-normal)

944Black-

vestigial

206Gray-

vestigial

185Black-normal

b+ vg+

b vg b vg

b vg b+ vg

b vg b vg

b vg+

Sperm

b vg

Parental-type offspring Recombinant offspring

Recombinationfrequency =

391 recombinants2,300 total offspring

100 = 17%

Human disorders

• Aneuploidy• Nondisjunction• Down syndrome• Klinefelter’s syndrome• Turner syndrome• Philadelphia chromosome• Deletion, duplication, inversion,

translation

Nondisjunction