zain ul abideen ppt file of genetics

1. GENETICS
MUHAMMAD ZAIN UL ABIDEEN

2. Gene:
• “Basic functional unit of heredity that maintain organism’s cells and
pass genetic traits to offspring”
• Each gene consist of specific nucleotide sequence
• Each gene codes for a specific protein
• All genes present in all cells (in form of heterochromatin or
(euchromatin)

4. Allele:
• “Alternative form of a gene (one member of a pair) that is located at a specific position
(loci) on a specific chromosome”
• Each gene have 2 alternative forms (each located on one homologue)
• These alternative forms of alleles may be same or different
• A person having different alleles of gene controlling a specific trait, will be called as
heterozygous for that trait

5. ABO
Gene IA
IB

8. • Such an allele that masks the effect of other allele in a pair is called
dominant allele and such trait is dominant.
• Such a trait or allele that appears in Fl in Mendel's genetics is called
dominant.
• For example, in pea plant, round (R) is dominant over wrinkled (r)

9. •Such an allele that is masked by another allele in gene pair is called
recessive allele and such trait is called recessive trait.
•Such a trait or allele is not appeared in FI but reappears in F2 in
Mendel's cross.
•For example, in pea plant, green (y) is recessive while yellow (Y) is
dominant.

11. •FI stands for first filial generation.
F2 stands for second filial generation

12. Phenotype:
•Physical appearance of a trait is called phenotype.
•For example, round and wrinkled are phenotypes of seed
shape which is a trait.

13. Genotype:
• Genotype is the genetic complement i.e. the genes in an individual for a
particular trait.
• For example, genotype of AB blood group is IaIb

15. Homozygous:
• When both alleles of a gene pair in an organism are same, the organism is
homozygous for that gene pair.
• An individual with homozygous genotype is called homozygote or true
breeding.
• For example, RR is genotype of homozygous round seeded pea plant

16. Heterozygous
• If both alleles of a gene pair are different from each other, the organism is
heterozygous for that gene pair
• An individual with heterozygous genotype is called heterozygote or hybrid.
• For example, Rr is genotype of heterozygous round seeded pea plant.

18. LAW OF
SEGREGATION

19. • Mendel selected pea plant (Pisum sativum) as experimental material due
to following
• Its flowers were hermaphrodite. It was normally self-fertilizing but could
be cross
fertilized.
• It has short generation time.
• It has many sharply distinct traits

21. Introduction:
• According to law of segregation, the two coexisting alleles for each trait in an
individual segregate (separate) from each other at meiosis, so that each
gamete receives only one of the two alleles. Alleles unite again at random
fertilization of gametes when zygote is formed.
• Law of segregation was developed through monohybrid cross (varying in one
trait).

23. RESULTS:
•Yellow is dominant over green.
•Phenotype ratio of F2 generation is 3:1
•Genotype ratio of F2 Generation is 1:2:1.

24. TEST CROSS.
IT IS A MATING IN WHICH AN INDIVIDUAL
SHOWING A DOMINANT PHENOTYPE IS
CROSSED WITH AN INDIVIDUAL SHOWING
ITS RECESSIVE PHENOTYPE

25. Definition:
• It is a mating in which an individual showing a dominant phenotype is crossed with an
individual showing its recessive phenotype
Significance:
This cross finds out the homozygous or heterozygous nature of the genotype
Details:
If round is crossed with wrinkled seeded plant and all offspring's are round seed
Seed producing then round of P1 will be homozygous
If round is crossed with wrinkled seeded plant and offspring's are obtained in
1:1 then round of P1 will be heterozygous.

26. LAW OF
INDEPENDENT
ASSORTMENT:

27. Introduction:
• Law of independent assortment is stated that when two contrasting pairs of
traits are followed in the same cross, their alleles assort independently into
gametes
• The distribution of alleles of one trait into gametes has no influence on the
distribution of alleles of the other trait
• Law of independent assortment was developed by studying dihybrid crosses (
varying in two traits).

29. Probability and Product rule:
• Probability is the chance of an event to occur e.g in F2 offspring of a monohybrid cross
the independent chance for a seed to be round is ¾.
• When two independent events are occurring simultaneously like in dihybrid cross the
ratio of each joint phenotypic combination can be obtained by multiplying the
probabilities of individual phenotypes.
• It is called product rule.

30. Event No. 1
Seed Shape
Independent Probability
Event No. 2
Seed Color
Independent
Probability
Both Events at a Time
Seed Shape and Color
Joint Probability
Round = 3/4 Yellow = 3/4 Round Yellow = 3/4 × 3/4 = 9/16
Round = 3/4 Green = 1/4 Round Green = 3/4 × 1/4 = 3/16
Wrinkled = 1/4 Yellow = 3/4 Wrinkled Yellow = 1/4 × 3/4 =
3/16
Wrinkled = 1/4 Green = 1/4 Wrinkled Green = 1/4 × 1/4 = 1/16

31. Limitations of Law of Independent assortment:
• Genes are located on chromosomes of specific loci Independent
assortment of genes depends upon independent assortment of their
chromosomes.
• All the genes present on a homologous pair of chromosomes are linked
to each other in the form of a linkage group. These cannot assort
independently.
• Those alleles assort independently whose allels are riding non
homologous chromosomes.