GENETICS Flashcards
father of genetics
GJ Mendel
father of modern genetics
W Bateson
father of experimental genetics
Th Morgan
father of human genetics
carrod
term gene was given by?
Johannsen
genotype and phenotype term was given by?
Johannsen
who rediscovered Mendelism?
Carl Correns, Tschermak, Hugo de Vries
trick: - chemistry test was hard.
in year 1900
experimental year of Mendal?
7 years (1856-1863)
“experiment in plant hybridization “ paper was pulished in journal in 1865
incomplete dominance was first discovered by?
carl Correns ; in mirabilis jalapa
chromosomal theory of inheritance was given by?
Sutton and Theodor Boveri
Quantitative inheritance was first time studied by?
J kolreuter
cytoplasmic inheritance was discovered by?
Correns
who gave experimental verification of chromosomal theory?
TH Morgan
Linkage was first time observed by?
Bateson and Punnet
term linkage and detailed studied by?
TH morgan
unit of inheritance/heredity?
gene
What is hemizygous term?
condition in which only single allele of a gene is present
e.g.-human males are hemizygous for sex linked genes
pre Mendelism scientists? and their postulates?
trick -
Most-moist vapor P-Pythagoras
Famous-fluid E- Empedocles
Rahul-reproductive A-Aristotle
Pyari-preformation S-Swammerdam
Priyanka-pangenesis Dal se- Darwin
Gandhi ko-germplasm Wish kiya-Weisman
Back cross
performed between F1and one of the parent
test cross
individual crossed with pure recessive genotype
objective- to know whether individual is homozygous or heterozygous
>if all tall progeny produced - homozygous dominant condition
>if 50% tall and 50% dwarf progeny produced- heterozygous condition
Mendel studied 7 pair of contrasting traits name them with chromosome no?
trick -
1 - FirSt - C (flower colour and seed colour)
4 - remaining (flower position, shape of
pod, length of plant)
5 - PC (pod colour)
7 - SS (seed shape)
describe Mendel’s experimental techniques
step 1- selection of pure breed
step 2 - hybridization between plants
Emasculation
Bagging
Dusting
Rebagging
Tagging
Crossing
Seed collection
step 3- selfing of F1 to btain F2
Law based on monohybrid cross
- Law of paired factors
- Law of dominance
Mendel formulated law of purity of gamete on the basis of which type of cross?
Monohybrid crossing
Genotype and phenotype ratio in F2 generation in monohybrid cross
PR-3:1
GR-1:2:1
Law based on dihybrid cross
- Law of segregation
2.Law of independent assortment
Genotype and phenotype ratio in F2 generation in Dihybrid cross
PR-9:3:3:1
GR-1:2:1:2:4:2:1:2:1
Intragenic/ allelic interactions
interaction between alleles of same gene
Intergenic/non allelic interactions
interaction between allele of two different gene
example of intragenic / allelic interactions
1.Incomplete dominance
2.Co dominance
3.Multiple alleles
4.Pleiotropic gene
example of intergenic/non allelic interactions
1.complementary gene
2.Epistatic gene
3.Supplementary gene
what are qualitative characters?
characters which are independent of number of dominant allele
what are quantitative characters?
characters which depend on number of dominant alleles
Example of Incomplete dominance
- flower colour in Miraibilis jalapa/4 “o”
clock/Gul e Bansi
2.flower colour in Antirrhinum
majus/snapdragon/Dog flower
3.size of starch grains in pea plant(pisum
setivum)
Genotype and phenotype ratio in F2 generation in Incomplete dominance
PR-1:2:1(Red:Pink:White)
GR-1:2:1(RR:Rr:rr)
phenotype of F1 in Incomplete dominance
all pink flower; F1 hybrid does not resemble to any of the parent
in heterozygous condition an intermediate phenotype appear
describe incomplete dominance
in this condition dominant allele is not fully dominant over recessive allele so in heterozygous condition an intermediate phenotype appears
describe codominance
in this interaction in heterozygous condition both allele are equally dominant and show their independent expression
example of codominance
1.skin colour of short horned cattles
when a black parent crossed with white
parent , a Roan colored F1 progeny is
produced
2.AB blood group system
3.carrier of sickle cell anemia
Genotype and phenotype ratio in F2 generation in Co dominance
PR- 1:2:1
GR-1:2:1
phenotype of F1 in Co dominance
F1 hybrid resemble both parents(mosaic inheritance), intermediate phenotype does not occur
describe multiple allelism
> more than two alternative form of a gene
multiple allele is formed due to mutation
multiple allele is located on same locus of
homologous chromosome
a diploid individual can have only two
allele of a gene and other allele can be
seen in other members of population
type of different possible genotype and phenotype in multiple allelism
n/2 x (n+1) and (n+1)
example of multiple allelism
- ABO blood group system (3)
- eye color in drosophila melanogaster(15)
describe pleiotropic gene
gene which control more than one character
these gene shows multiple phenotypic effects
examples of pleiotropic effect
1.seed shape and size of starch grain in pea
plant are controlled by the same gene
located on 7th chromosome.
(for seed shape B gene shows Dominance over b gene)
(for size of starch grains B gene shows incomplete dominance over b gene)
2.Phenylketonuria (autosomal recessive)
(most of the human genetic disorders are pleiotropic)
3. Sickle cell anemia (autosomal recessive)
describe complementary gene
two pairs of non-allelic dominant gene shows a similar effect in independent condition.
but produce a new trait when present together in dominant form (at least one dominant allele of both gene must be present to express new trait)
complementary gene studied by ?
Bateson and punnet
studied on lathyrus odoratus (sweet pea)
phenotypic ratio of F2 in complementary gene
PR-9:7
(C_P_)-9
(C_pp)-3
(ccP_)-3
(ccpp)-1
genotypic ratio of F2 in complementary gene
1:2:1:2:4:2:1:2:1
describe Epistasis
a gene prevent the expression of another non allelic gene also known as inhibiting gene
epistasis reduces the number of phenotypes appearing in F2
both non allelic gene may be mutually epistatic to each other
gene whose effect get suppressed in epistasis?
hypostatic gene
types of epistasis
dominant and recessive epistasis
describe dominant epistasis
one dominant inhibiting gene is enough to suppress the expression non allelic gene
phenotypic and genotypic ratio in dominant epistasis
PR-12:3:1(white:yellow:green)
GR- 1:
example of dominant epistasis
fruit colour in summer squash(cucurbita pepo)
Phenotypic and genotypic ratio in dominant epistasis
PR - 12:3:1 (white:yellow:green)
A=dominant allele for yellow
a=recessive allele for green colour
B=Epistatic gene over A & a gene
A_B_=9white
A_bb=3yellow
aaB_=3white
aabb=1green
GR -1:2:1:2:4:2:1:2:1
Example of recessive epistasis
Color of onion bulb and color of rat
Describe recessive epistasis
A recessive homozygous genotype at one locus (aa) supress the expression of not allele at another locusa (B_)
Phenotypic and genotypic ratio of recessive epistasis
PR=9:4:3
ii = epistatic gene
I_R_=9 red
I_rr= 3 yellow
iiR_=3 white
iirr = 1 white
GR=1:2:1:2:4:2:1:2:1
Describe supplementary gene
Two non allelic gene which produce their own effect independently when present in dominant state and also interact to form a totally new trait (with both dominant )
Example of supplementary gene
Comb types in poultry
Phenotypic and genotypic ratio in supplementary gene
PR=9:3:3:1
P_R_= 9 walnut comb
P_rr= 3 pea comb
ppR_ = 3 rose comb
pprr = 1 single comb
GR =1:2:1:2:4:2:1:2:1
Describe duplicate gene
When a non allelic gene determine the same phenotype so that either of the gene is able to produce the character in question
Example of duplecate gene
Fruit shape in shephered’s purse , cucurbita pepo (additive duplicate gene condition , {T_D_}= shape change)
In cucurbita pepo F2 ratio = 9: 6:1
Phenotypic and genotypic ratio in duplecate gene
PR = 15:1
T_D_= triangular shape
T_dd = triangular shape
ttD_= triangular shape
ttdd = enlongated shape
GR =1:2:1:2:4:2:1:2:1
Type of phenotype in polygenic inheritance
2n+1
Phenotypic ratio in polygenetic/Quantitative/ human skin color inheritance
PR = 1:6:15:20:15:6:1
20 - mulatto
Contribution of each dominant allele in polygenic inheritance
Maximum expression - minimum expression/ total number of dominat allele
Inheritance of cytogene occurs through male or female ?
Female
What is cytogene
Extra nuclear gene
Total cytogene in a cell is called?
Plasmon
Relation between strength of linkage and crossing over
Strength of linkage is inversly proportional to crossing over
Describe linkage group
All the gene which are located on one pair of homologus chr form one linkage grp
Gene which are present on same homologus chr are inherited together
No of linkage group in diploid individual is ?
No of haploid no of chromosome
No of linked grp in drosophila is ?
4
No of linked grp in human is ?
23
In male linked grp = 24 due to y gene
What is cis/coupling arrangement of linked genes?
When all dominant allele of a gene is present on same homologus pair of chr
And all recessive allele of the gene present on other pair of homologus chr
++/ab
No of linked grp in pisum sativum is ?
7
What is trans / repulsion arrangement of linked gene?
+b/a+
What is recombination frequency or cross over value
No of recombinant/total no of offspring x 100
1st chromosomal map of drosophila was prepared by whom?
Alfered sturtevant
Chromosomal map provide information about ?
Distance between two linked gene
Sequence of different linked gene
%age of recombinant in body / eye color experiment in drosophila by morgan
1.3%
%age of recombinant in eye color& wing size experiment in drosophila by morgan
37.2%
