a complete understanding of variation and genetics. how changes in genetics inherit and how genetically disease inherited... Complete info on Mendelian inheritence

1. VARIATION & GENETICS
CHAPTER 22
2ND YEAR BIOLOGY

2. Gene Pool

3. MENDLE’S LAWS OF INHERITENCE

4. Seven Contrasting Pairs studied by
Mendle

5. Due to its short life span
Short time between generation
Rapid growth
Many generations can be raised within short period of
time
Capability of self fertilization as well as cross fertilization
Easy to handle

6. Monohybrid Cross
F3 Generation results
1/3 of F2 Round produced only round
(True breeding like P1)
2/3 of F2 round produced both round
and wrinkled in 3:1 ratio(Monohybrids
like F1 round)
F2 wrinkled produced wrinkled

7. Mendles’s Interpretation
Particulate Herditary Factor (Elementen)
Homozygous (RR)________Homozygote
Hetrozygous(Rr)_________Hetrozygote
F1 Segregation
Gametes 1/2 1/2
Rr
R r
Monohybrid Cross Interpretation
Phenotypic Ratio 3:1
Genotypic Ratio 1:2:1
1/4 = RR (Homozygous round)
2/4 = Rr (Hetrozygous round)
1/4 = rr (Homozygous Wrinkled)

8. Used to test the genotype of an individual
showing a .dominant phenotype

10. Probability is chance of an event to occur
In monohybrid cross there is a independent chance for a seed to be round is ¾ or wrinkled ¼.
When two independent events are occurring simultaneously
the ratio of each joint phenotypic combination
can be obtained by
multiplying the probabilities
of individual phenotypes and it is a product rule.

12. Independent assortment of genes depends upon independent assortment of their chromosomes
The genes present on homologous chromosomes does not assort independently henxe co assortment
happened.
They are linked on homologous chromosomes as linkage group.
Mendles knew nothing about chromosomes
The traits studied by Mendle confined to these four chromosomes who assort independently while
other three present far away from each other on homologous chromosomes hence no linkage
possible so assort independently.
1865---Mendle presented his work to Brunn Society for study of natural Science
1866—work Published
1990 his work was rediscovered and acknowledged after 34 Years

14. 1) Complete Dominance
2) Incomplete Dominance
3) Codominance
4) Over Dominance

15. Incomplete Dominance

16. Codominance

18. Over Dominance
In over dominance the expression
of heterozygous allele become
more dominant than both
homozygous allele

19. Genes having more than two altered forms or alleles are multiple alleles
Well understood by ABO blood group System in humans.

20. Karl Land
Steiner in
1901
Encoded by
single
polymorphic
gene I on
chromosome 9.
Gene has three
multiple alleles
IA, IB and i.
Blood group
start their
expression at
early embryonic
stage and keep
on expressing
till death.

21. Anti Bodies appear in Plasma
during few months after birth
Naturally occurring in absence
of corresponding antigen
Phenotype A will agglutinate or
clump any RBC with B antigen
and vice versa
AB phenotype has neither A nor
B Antibody and O phenotype
has neither A nor B Antigen
The Blood serum
containing antibodies is
called antiserum
Any blood transfusion is safe if
its not causing agglutination in
recipient.
Agglutination leads to serious
results because clumped cells
can not pass through fine
capillaries ultimately leading to
capillary blockage.

22. A child having AB Phenotype
can nor be the child of O type
phenotype
Similarly Blood group type B can
not be the father of child having
A type phenotype whose
mother is of phenotype O.

23. Rh Blood Group System
Encoded by three genes C,
D and E which occupy two
tightly linked loci.
Allele of D occupy one
locus while other locus is
occupied by C and E
alternatively.
Prime importance is of D.
Gene D has two alleles D
(dominant) and d
(recessive).
DD or Dd= Rh+
dd= Rh-
Rh antibody production
requires stimulus from
respective Rh antigen.

24. Erythroblastosis
foetalis
If Fathers genotype is DD
then all of their offspring
Rh+ and
If the genotype is Dd then
half of their offspring Rh+.
Liver and Spleen of baby swell
due to rapid production of RBC.
The breakdown product of RBC
is Bilirubin.
Bilirubin damages brain cells
and turns his skin and whites of
the eye yellow. (Jaundice)

25. When an effect caused by a gene or gene pair at one locus interferes with or hides the effect
caused by another gene or gene pair at another locus.

26. Expression of IA or IB gene
depends upon another gene
present on chromosome no.19.
H gene insert a precursor
substance which insert a sugar
molecule onto surface
molecule (glycoprotein) of RBC.
Respective antigen then attach
to that sugar molecule
But the recessive hh gene lack
that precursor and no sugar
molecule is inserted. Antgens
don’t get space to adhere hence
fall away.
Their RBCs lack antigens A or
B but genes IA and IB
present. So they look
phenotypically O but they
are not O genotypically

31. Numerous characters controlled by thousands of genes residing on limited no of chromosomes.
All genes present on homologous chromosomes linked together through linkage group.
staying together of all of genes together on same chromosome is called linkage.
No of linkage group corresponds to the no of homologous pairs of chromosomes present.
genes for colour blindness, haemophilia, gout etc form 1 linkage group on X chromosome.
Gene for sickle cell anemia, leukemia and albinism make another linkage group on human
chromosome 11.
Gene linkage minimizes the chances of genetic recombination.

33. Exchange of segments
between non sister
chromatids of homologous
chromosomes during
meiosis.
Crossing over produces
genetic variations among
offspring's

35. Proportion of recombinant types between two gene
pairs as compared to sum of all combinations
Recombinant frequency is directly proportional to
distance b/w the linked gene loci.
Genes can be mapped on a chromosome on the basis
of their recombination frequency.

36. SEX CHROMOSOME
8 chromosomes in 4 homologous pair
Morgan notices notable difference in male and female
drosophila
Female had 2 similar rod shaped x chromosome
Male had one rod shaped x chromosome but other
morphologically different j shaped Y chromosome

37. 46 chromosomes in 23 pairs are present
23rd pair is different and is call sex chromosome
Male is heteromorphic having a x and a very short y
chromosome
Female is homomorphic having same 2 x chromosomes
SRY is male determining gene
Male= 11 pairs of autosomes with only 1 x chromosome
Female= 11 pairs of autosomes with 2 x chromosome

38. XX-XO TYPE
XY-XX TYPE
ZZ-ZW TYPE

39. XX-XO Type

40. XX-XY type

41. ZZ-ZW Type

42. Syndrome Drosophila Humans
Turner’s Syndrom
(XO)
Sterile male Sterile female
Klinefelters Syndrome
(XXY)
Sterile Female Sterile male

43. X-Y System
X-chromosome autosome balance system for sex determination
Correns (1970) discovered pollens to be sex determining
Many microorganisms like Yeast don not have sex chromosomes
Depends on genic system for determination of sex

48. GENETICS OF HAEMOPHILIA

49. Normal trichromatic colour vision is based on three kinds of
cone cells
Red Opsin is on X Chromosome
Green Opsin is on X Chromosome
Blue Opsin Is in Autosome 7
Mutation in opsin genes gives 3 types of blindness
Dichromat---perceive 2 primary colours
Monochromat—perceive one coloue
Tricchromat—perceive no colour
Protanopa—Red Blindness
Deuteranopa—Green Blindnedd
Tritanopia—Blue Blindness

52. LIMITED TO ONE SEX DUE TO ANATOMICAL DIFFERENCE
Affects structure present only in males or females
E.g. Genes for milk yields in Cows
SEX INFLUENCES TRAIT
Occurs in both male and females but more common in one sex
Controlled by allele that is dominant in one sex but recessive in other sex.
E.g. Baldness

53. Type I IDDM & Type II NIDDM
Type I-- immune disorder
Insulin gene is located on short arm of chromosome 11
Polymorphism and genetic variation within this locus is responsible for diabetes Type I
susceptibility
Multifactorial or Polygenic
MODY
Blood Pressure is also a multifactorial trait.

54. https://youtu.b
e/FrpDuekMX8
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