PLNT3140 Introductory Cytogenetics

Lecture 15

October 31, 2017

MAPPING GENES TO CHROMOSOMES


Learning checklist:

1. Understand how the term "allele" can be applied to mutations at the DNA level, including silent mutations, missense mutations, nonsense mutations, insertions and deletions.

2. Understand why most mutations in eukaryotes are selectively neutral.

3. Understand the methodology behind RFLPs.

4. Understand how molecular markers such as RFLPs segregate according to the laws of Mendel. Be able to calculate linkage distance between two loci in a two point test cross.

5. Understand why genetic linkage cannot be directly calculated from progeny ratios in 2 point crosses.





I. MAPPING A PHENOTYPE

A.  A molecular definition of "allele"


Divergence of protein sequences during plant evolution.

Amino acids from the N-terminal region of thionin proteins from several plant species are shown. Where amino acids have been inserted or deleted during the course of evolution, gap (-) characters have been inserted to optimize the alignment of homologous positions within the proteins.


The Universal Genetic Code
UUU
UUC
UUA
UUG
phe

leu
UCU
UCC
UCA
UCG
ser UAU
UAC
UAA
UAG
tyr

stop
stop
UGU
UGC
UGA
UGG
cys

stop
trp
CUU
CUC
CUA
CUG
leu
CCU
CCC
CCA
CCG
pro CAU
CAC
CAA
CAG
his

gln
CGU
CGC
CGA
CGG
arg
AUU
AUC
AUA
AUG
ile


met
ACU
ACC
ACA
ACG
thr AAU
AAC
AAA
AAG
asn

lys
AGU
AGC
AGA
AGG
ser

arg
GUU
GUC
GUA
GUG
val GCU
GCC
GCA
GCG
ala GAU
GAC
GAA
GAG
asp

glu
GGU
GGC
GGA
GGG
gly

B. RFLP's (Restriction Fragment Polymorphisms) are molecular alleles

parents.gif
Restriction maps of the seven Adh 1 chromosomal regions. The boundaries of the transcription units are denoted by the vertical dashed lines, and the region that hybridized with the ADH1-cDNA probe, pZML84, is also shown. Undisplayed Graphic

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