4 genetics - gene linkage (by elizabeth)

Elizabeth Jeon

•Define linkage group (10.2.4)

•Explain an example of a cross between two linked genes. (10.2.5)

•Identify which of the offspring in such dihybrid crosses are the recombinants. (10.2.6)

Assessment Statements

Normal Dihybrid CrossesPpGg x ppgg

• P - normal skin

• p - prune skin

• G - nomral gait

• g - grasshopper gait P P

p p

G G

g g

p p g g

p p g g

Normal Dihybrid CrossesPpGg x ppgg

P

Pp

pGG

gg

PG pGPg pg

pg PpGg PpggppGg ppgg

INDEPENDENT

ASSORTMENT

p p g g

p p g g

Linked Genes• Group of genes whose loci are on the same chromosome

CcGg x ccgg• C- normal

skeleton

• c - malformed skeleton (csp)

• G - nomral gait

• g - grasshopper gait

C C c cG G g g

GC

GC

cg

cg

g gc c

g gc c

CG cg

cg CcGg ccgg

PARENTAL!

CcGg ccgg

YET, crossover

C C c c

G G g g

- @ Prophase I in Meiosis

YET, crossover

YET, crossover

Chiasmata

YET, crossover

YET, crossover

YET, crossover

C

G

c

g

c

g

C

G

Frequency of cross over depends on Distance between linked gene

Distance between linked gene

Linked Genes• Group of genes whose loci are on the same chromosome

CcGg x ccgg

C C c cG G g g

g gc c

g gc c

CG cg

cg CcGg ccgg

PARENTAL!C

G

c

g

c

g

C

G

Linked Genes• Group of genes whose loci are on the same chromosome

CcGg x ccgg

C C c cG G g g

g gc c

g gc c

CG cg

cg CcGg ccggC

G

c

g

c

g

C

G

Cg cG

Ccgg ccGgRECOMBINENT

!

Ccgg ccGg

13%87%

How to distinguish recombiant

•In test cross of GC

GC

c g

c g

C g c GOR !!

Thank you