Genetics Module 2.2 Flashcards
are genes located on the same chromosome
Linked genes
are often inherited together into the same gametes
linked genes
these are closely associated linked genes that are always inherited together
complete linkage
these are associated linked genes that partially segregate from each other during gamete formation
incomplete linkage
types of linkage notation
- Cisform or coupling phase
- Transform or repulsion phase
linkage notation
All dominant alleles (AB) or recessive alleles (ab) are on the same chromatid.
Cis form or coupling phase
linkage notation
Both the dominant allele and recessive allele of linked gene A and B are on the same chromatid.
Trans form or replusion phase
it is the process of determining if two genes are linked, or if they tend to be inherited together
linkage determination
types of linkage determination
- deviation
- non-comfornity
linkage determination
1:1 (monohybrid) and 1:1:1:1 (dihybrid) test cross ratio
deviation
linkage determination
9:3:3:1 F2 phenotypic ratio
non-comfority
linkage determination
formula for linkage value
linkage value= (total number of crossover types/total number of population) x 100
refers to the inhibition of further cross over events by crossover event in a nearby region of the chromosome
interference
is the ratio of the observed number of double crossovers to the expected number of double crossovers
coefficient coincidence
formula for coefficient coincidence (cc)
cc= actual DCO/expected DCO
formula for interference
i= 1-cc
is a diagram showing the relative positions of genetic markers along a chromosome that is determined by the recombination frequency during crossover of homologous chromosomes.
linkage or genetic map
who discovered linkage map
Thomas Hunt Morgan (1910)
is based on the crossing over percentage obtained from genetic experiments where 1 map unit is equivalent to 1% crossing over.
map distance
unit of measurement for linkage map
cM (Centimorgan)
Factors Affecting Recombination Frequencies
In general, the heterogametic sex (XY in males) of a species has lower crossover frequencies
sex
Factors Affecting Recombination Frequencies
- sex
- maternal age
- temperature
- cytoplasmic effect
- nutriton
- chemical effects
- radiation
- genotype
- chromosome structure
- centromere
Factors Affecting Recombination Frequencies
Crossing over tends to decrease as ________ increases
maternal age
Every cell of sexually reproducing organism was bisexual – full potential to express both (male & female phenotype) or either one those. This theory help explain bisexuality, hermaphroditism, sex reversal and intersexuality in plant and animals.
sexuality theory
