Genetics Flashcards
Term genetics was coined by
Bateson.
Father of genetics is
Gregor John Mendel
Living organism studied in classical genetics is/was
Pea plant (pisum sativum) = garden pea Mendel also tried to work on Hawk-weed (Hieraceum).
Which technique is used in classical genetics
Hybridization
Father of modern genetics is
Bateson
Father of experimental genetics is
T.H.Morgan
Aka flyman of genetics (bcz he worked on fruitfly)
Living organism studied in modern genetics was/is
Fruitfly ( Drosophila melanogoster) and Pink bread mould (Neurospora crassa) aka drosophila of plant kingdom.
Father of human genetics is
Sir Archibald Garald.
Worked on a genetic disorder c/d Alkaptoneuria.
Drosophila of plant kingdom is
Pink bread mould (Neurospora crassa).
What’s Eugenics?
Improvement in human race by application of genetics.
Whats euphenics?
Application of genetics for treatment of genetic disorders.
Whats euthenics?
Improvement in human race by providing proper environment.
Diagynic inheritance?
Transmission of charac. from male to male “via female”.
Dia=via ; gynae=female
Diandric inheritance?
Transmission of charac. from female to female “via male”.
Dia=via ; andric =male
Holoandric inheritance?
Transmission of charac from male to male to male and so on.
Holo=complete ; andric =male
Hologynic inheritance?
Transmission of charac from female to female to female and so on.
Holo = complete ; gyna =female
Name the modes of transmission (found in majority).
Diagynic
Diandric
Hologynic
Holoandric
Physical basis of heridity is
Gene
Chemical basis of heredity is
DNA 🧬
_________ is the basis of heredity. [ncert]
Inheritance
Who first time applied statistical analysis & mathematical logic to problems in biology?
Mendel.
During his investigations into inheritance patterns…
Pre-formation theory was given by
Swammerdam
Found small humans inside head of sperms and c/d them homunculus.
Theory of pangenesis was given by
Darwin.
Theory of continuity of germplasm was given by
Weisman.
Said: somatoplasm isn’t inherited (mortal) whereas germ plasm is inherited (immortal).
Sutton & boveri gave ______ theory regarding heredity.
Chromosomal theory of inheritance.
Discontinuous variations (org. is deviated from normal) occur due to
Exposure to some mutagens (x-rays, gamma rays, uv rays, silver nitrate, benzopyrene etc)
Continuous variation (org. isn’t deviated from normal) occur due to
Crossing over.
D.O.B of Mendel
20th July, 1822 in Hezendorf, Austria. “(Austrian monk)”
Mendel cultivated plants for 7 yrs from ____to ___.
1856-63 : he cultivated 25,000 pea plants.
Mendel published his work/paper in
1865.
Death of Mendel
6th jan,1884 due to chronic nephritis (kidney failure).
Main reason for Mendel’s success was
Luck
Other reasons for Mendels success are
Luck
Hardwork
Scientific attitude
Mathematical background
Who re-discovered Mendels work and when?
In 1900, 3 scientists- Hugo de vries, Correns, Tschemark re-discovered Mendel’s work.
1900 => 16 yrs after his death or 34yrs after his publication
Name the dutch scientist who re-discovered Mendel’s work?
Hugo de vries from Holland ( dutch )
Correns was from Germany and Tschemark was from Austria.
T/F
True.
Who re-published Mendel’s work and in which journal?
Hugo de vries re-published Mendel’s work in ‘Flora’ in 1901.
Term gene was coined by
Johnssen.
Gene aka medelian factor aka factor.
Term allele was coined by
Bateson
Dominant allele is the one that expresses in
Heterozygous condition only.
Number of traits selected by Mendel were??
14 i.e 2x7 characters
Complete the table:(in order that chr.no. follows 4414571 ) Characters studied by Mendel | Dominant | Recessive | Chr.no. 1) 2) 3) 4) 5) 6) 7)
Hgt. Of plant _ Tall _ Dwarf _4 Flower position _Axial _Terminal _4 Flower colour _Violet _white _1 Pod shape _inflated _constricted _4 Pod colour _green _yellow _5 Seed shape _round _wrinkled _7 Seed colour _yellow _green _1
Note:to denote these, consider 1st letter of each dominant charac.
Egs., Violet => V => VV & vv
Characters studied by Mendel are present on __ chromosomes with no.s __,__,__,__.
4 chromosomes
I.e 4,1,5,7
No. Of gametes formed =
2^n
Where n is the no. Of heterozygosities.
Eg., AaBbCCeeDd
Here n=3 as Aa , Bb & Dd are heterozygous where as CC & ee are homozygous.
=> no. Of gametes = 2^3=8
**on how to make these gametes, refer notebook.
Phenotypic ratio for mono hybrid cross is
3:1
I.e tall:dwarf = 3:1 or round:wrinkled or dominant:recessive type
Genotypic ratio for mono hybrid cross is
1:2:1
TT : Tt: tt type
Phenotypic ratio for di hybrid cross is
9:3:3:1
T,R : T,r : t,R : t,r type
Genotypic ratio for dihybrid cross is
1:2:1:2:4:2:1:2:1
To know how this looks in punett square refer notebook
In general, phenotypic & genotypic ratio is given by
Phenotypic ratio = (3:1)^x where x is cross no.
Genotypic ratio = (1:2:1)^x where x is cross no.
For mono hybrid cross, cross no.=1
For dihybrid cross, x = 2 …. so on
1) Phenotypic & genotypic ratio remains same for reciprocal cross.
2) By exchanging parents, there’s no change in phenotypic or genotypic ratio.
Both statemnets are correct & 2 maybe regarded as correct explanation of 1.
As, cross obtained by exchanging the parents is K/a reciprocal cross.
Whats back-cross?
Cross of f1-generation with its parents.
Back-cross = f1 x parent
F1 x dominant parent =
F1 x recessive parent =
F1 x dominant parent = out-cross
F1 x recessive parent = test-cross
Mono hybrid test cross ratio =
1:1
I.e dominant:recessive
Dihybrid test cross ratio =
1:1:1:1
Name laws of inheritance
Law of dominance. [ 1st law as per ncert]
Law of unit factors.
Law of segregation. [ 2nd law as per ncert] {@1}
Law of independent assortment. {@2}
{actually 1st law, 2nd law}
State Mendel’s 1st law?
Aka law of dominance.
States that :
i) Characters are controlled by discrete units cd factors/genes.
ii) Factors occur in pair.
iii) In heterozygous condition one gene dominates (dominant) the other is recessive.
Exceptions of law of dominance?
Multiple allelism
Incomplete dominance
Co-dominance
Differential dominance
Concept of incomplete dominance was given by
Correns
Intermediate phenotype is produced in
Incomplete dominance.
Examples of incomplete dominance are
Flower colour in 4 o clock plant (mirabilis )=red/pink/white
Flower colour in snap dragon = red/pink/white
Feather coat colour in case of Andulasian foul =black/blue/white
Starch synthesis in pea = large/medium/small sized
Whats the phenotypic & genotypic ratio in incomplete dominance?
Phenotypic as well as genotypic ratio is 1:2:1
Presence of more than 2 alleles for a single gene is called
Multiple allelism
Examples of multiple allelism are
ABO-Blood group system
Skin coat colour in case of rabbits = agouti /chinchilla /Himalayan albino / albino
No. of phenotypes & genotypes ,of ABO blood group system ,respectively are
4 & 6
4= A/B/AB/O
6= iaia/ibib/iaib/ioio/ibio/iaio
No. Of possible combinations is
n(n+1)/2
Where n is no. Of alleles.
Used for qs like : if a gene has n alleles then no. Of combinations will be?
Condition in which both alleles of a gene are able to express equally in same organism is called
Co-dominance
Examples of co-dominance
ABO- blood group system
MN-blood group system
RS-blood group system
Father of blood groups is
Karl Landsteiner
He gave the concept of blood groups in 1901.
Whats blood group?
Concept based on presence or absence of different types of surface antigens present on the surface of RBC’s.
In humans __ types of blood group systems exist.
33
As reported by ISBT (international society for blood transfusion) in 2012.
A/B/O blood groups where discovered by ______ & AB was later discovered by ______.
Landsteiner (1901)
de-Castello (1902)
A-blood group has: Antigen-A Antibody-A Both None
Has antigen-A
Produces anti-B
Can receive from A and O
Universal recipient/acceptor is
AB-blood group
As it has antigen-A as well as antigen-B
Produces neither anti-A nor anti-B
Can receive from A,B,AB,O
Most common type of blood group in world is
O
Rh-blood group system was discovered by
Eischer.
He Studied RBC’s of monkeys (Rhesus)
9q34 represents
On chromosome 9, long arm, 34th gene
In humans, 9q34 Has 3 alleles ia / ib / io
In humans on chromosome 1, long arm, 35th gene i,e 1q35 has 2 alleles. Name them.
Ia / Ir.
IRIR or IRIr represents
Rh-positive blood group
Has antigen-Rh
doesn’t produce anti-Rh, so it can receive from Rh +ve & Rh -ve
Can Rh-ve blood group receive blood from Rh+ve
No.
Bcz it produces anti-Rh.
Universal recipient is
AB+ve
Universal donor is
O-ve
Blood group testing is based on
agglutination reaction (clumping of cells).
Many gene 1 character expression is called
Polygeny.
________ is aka quantitative inheritance.
Polygeny.
Examples of polygeny are
Human skin colour
Kernel colour in wheat
Skin colour is controlled by ___ gene.
3 genes (AABBCC)
Total gene = 3
Total alleles = 6
XX-XY method is found in
Mammals
Drosophila
Some bryophytes
XX-XO method is found in
Grass hoper and cockroaches
ZW-ZZ method is found in
Birds
Reptiles
Fishes
ZO-ZZ method is found in
Butterflies
Moths
Haplo-diploidy is found in
Bees
Ants
Wasps
Sex id determined by environmental factors in
Turtles Lizards Crocodile Alligators Bonelia Cripidula American crocodile
Cytoplasmic inheritance concept was given by
Correns from 4O’ clock plant (mirabilis)
Whats cytoplasmic inheritance
Inheritance of plasma genes/cytoplasmic genes/extra-nuclear genes from parents to offsprings.
Properties of cytoplasmic inheritance are?
Shows maternal effect (more influence of mother on expres of such genes).
Reciprocal cross shows different result than normal cross. Therfore aka Non-Mendelian inheritance.
Controlled by plasma genes.
Gene mapping is difficult.
Chromosomal theory of ’linkage’ was given by
Morgan and Castle.
Postulates of chromosomal theory of linkage?
Genes present on same chromosome are termed as linked genes.
Linked genes have tendency to remain and inherit together.
Linked genes may occasionally get separated by crossing over.
Chances of separation depend upon strength of linkage.
Strength of linkage depends on distance b/w 2 genes.
Can linked genes be separated. If yes, then how?
Yes. Linked genes may get occasionally separated by crossing over.
Whats recombination frequency?
Recombinants upon tot. No. Of offsprings x 100
Its the %age of recombinants in any cross.
Recombinants = new combinations that were not present in parent.
Calculate the distance b/w 2 genes?
Measured indirectly using RF (recombination frequency).
Distance is said to be ‘x’ cM if RF is x%.
Unit = cM (centi-morgan)
10cM =
100cM =
10cM = 1dM (deci-morgan) 100cM = 1M (morgan)
Whats linkage groups ?
All genes present on one chromosome represent one linkage group.
No. Of linkages groups = haploid chromosome no.
No. Of linkage groups in humans is
23
No. Of linkage groups in human males and female is
Males = 44+X+Y = 24 Females = 44+XX = 23
No. Of linkage groups in pea plant is
7
In drosophila, no. Of linkage groups are
4
In ______ linkage, RF =0% i,e recombinants are not formed.
Complete linkage
In incomplete linkage, recombinants are formed in _______
Less frequency.
Examples of complete linkage are
Male-drosophila and female-silkmoth.
Characteristics of complete linkage?
No recombinants.
RF = 0%
Instead of 4 gametes, only 2 gametes are formed.
Test cross ratio is 1:1 instead of 1:1:1:1
Rare phenomenon.
Characteristics of incomplete linkage?
Recombinants are formed in less frequency.
All 4 types of gametes are formed.
Test cross ratio is deviated from 1:1:1:1
In sweet pea , obtained test cross ratio is
7:1:1:7
BL:Bl:bL:bl
Numericals on linkage
If M&N are incompletely linked , then recombinants will be formed though in less frequency, so the no. Of gametes will be same as we calculated 2^n where n is no. Of heterozygosities. “Solve as if incomplete linkage isn’t written in qs”.
If M&N are completely linked, consider linked genes as one heterozygosity and others independently.
*for better understanding see examples from notebook.
Chromosomal theory of inheritance was given by
Nilson & Stevans.
Acc, to this theory,orgs have 2 types of chr.; autosomes and sex chromosomes.
Genic balance theory was given by
Bridges.
Acc. to this theory, sex is determined by value of X/A ratio.
Where x= no. Of chr.
A = ploidy level of autosomes.
Different values of X/A represent what acc. To genic balance theory?
If value of X/A is <0.5 —> super male =0.5 —> male B/w 0.5 & 1 —> inter-sex =1 —> female >1 —> super female
Whats sex-linked traits?
Genes responsible is present on sex-chromosome.
Eg.s Haemophilia, colourblindness , DMD.
Sex-limited traits?
Gene responsible is present on autosomes.
Gene is expressed in ‘only one sex’.
Eg.s breast development in females, beard development in males, plumage formation in peacock.
Sex-influences traits?
Gene responsible is present on autosome.
Expresses ‘more in one sex’.
Eg.s paternal baldness, muscle development.
Holoandric traits?
Gene responsible is present on Y-chromosome.
Eg.s, hypertrichosis (hair growth in ear), percupine males (standing hair [khade baal] ), webbed toes.
In sex-linked inheritance, there is variation in ratio of reciprocal cross.
T/F
True.
Eg.s eye colour in drosophila.
Who suggested that recombinant frequencies can be utilised in predicting the sequence of genes on the chromosome?
A.H.Sturtevant
Who prepared first chromosomal map or genetic map for drosophila?
A.H.Sturtevant
Chromosomal theory of inheritance was proposed independently by
Sutton & boveri
%age of recombinant type b/w genes y & w in Drosophila?
1.3%
Rest 98.7% is parental type.
%age of recombinants b/w genes w & m of Drosophila?
37.2%
Rest 62.8% is parental type
Who used the frequency of recombination b/w gene pairs on the same chr. to measure distance b/w genes and mapped their position on the chromosome?
Alfred Sturtevant
Sex-linked diseases in humans is
Colour blindness & haemophilia
SCA, Thallasemia, phenyl ketonuria is autosomal recessive disorder.
True
Turner’s syndrome is due to
Monosomy of sex-chr.
44+XO
Klinefelter’s syndrome is due to
Trisomy of sex-chr.
44+XXY
Down’s syndrome is due to
Mostly due to trisomy of 21st chromosome.
