Karaganda University
Faculty of Chemistry
Patterns of inheritance
of characters and
principles of heredity.
Checked by: Blyalova J. J.
Prepared by: Maratova Ayaulym,
Bibala Kuralay
Group: HB-31
Plan:
1. What is heredity ?
2. Law of Dominance
3. Law of Segregation
4.The Law of Independent Assortment
Conclusion
Objectives:
●
●
●
●
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Explain Gregor Mendel’s laws of inheritance
Discuss the difference between genotypes and
phenotypes
Label the three types of genotypes
Draw and label a Punnett square
Predict outcomes of a Punnett square
Heredity
●
●
Heredity- passing of traits from parent to offspring
Traits- characteristics that are inherited
●
hair color, height, blood type, susceptibility to a certain disease (diabetes,
depression, obesity, breast cancer)
Genetics- the study of heredity
○
Gregor Mendel
• Austrian monk who formulated fundamental
laws of heredity in early 1860s
•
Studied science and mathematics at
University of Vienna
•
Conducted breeding experiments with the
garden pea (Pisum sativum)
•
Gathered and documented mathematical
data from his experiments
Mendel
●
●
●
Modern genetics had its beginnings in an abbey garden,
where a monk named Gregor Mendel documented a
particulate mechanism of inheritance.
He discovered the basic principles of heredity by breeding
garden peas in carefully planned experiments.
His approach to science had been influenced at the
University of Vienna by one of his professors: the physicist
Doppler.
Inheritance in pea
plants
Mendel followed the inheritance of 7 traits in pea
plants. He chose traits that had 2 forms:
Pea shape (round or wrinkled)
• Pea colour (yellow or green)
• Flower colour (purple or white)
• Flower position (terminal or axial)
• Plant height (tall or short)
• Pod shape (inflated or constricted)
• Pod colour (yellow or green).
•
Mendel’s Experiments
Mendel’s work
●
●
●
In order to study inheritance, Mendel chose to use
peas, probably as they are available in many
varieties.
The use of plants also allowed strict control over the
mating.
He chose to study only characters that varied in an
‘either-or’ rather than a ‘more-or-less’ manner.
Why pea?
Garden Pea
•
Easy to cultivate
•
Short generation time
•
Cross-pollination by hand
Self-Pollination
Involves having
the pollen (male
sperm) be directly
deposited on the
female section of
the flower
●
Cross- Pollination
Requires the
removal of the male
stamen (makes
pollen) on 1st flower
and transferring the
pollen from a
different flower
to the first one
●
Mendel’s terminology
●
●
●
True breeding: When the plants self-pollinate, all
their offspring are of the same variety.
Hybridization: Mating, or crossing, of two
varieties.
Monohybrid cross: A cross between two parents
that breed true for different versions of a single
trait.
Mendel’s terminology
●
●
●
P generation: True breeding parents.
F1 generation: (first filial) Hybrid offspring of the
P generation.
F2 generation: (second filial) Offspring from the
self-fertilisation of the F1 hybrids.
Genotypes
●
The genotype refers to the entire set of genes in
a cell, an organism, or an individual. A gene for a
particular character
or trait may exist in
two forms; one is
dominant (E) and the
other is recessive (e).
Dominant and Recessive Genes
●
Dominant Genes
○
●
One gene overshadows the other.
Recessive Gene
○
The gene that is overshadowed by a
dominant gene.
Phenotypes
●
Phenotype is the physical
appearance or other characteristic
of an organism as a result of the
interaction of its genotype and
the environment.
Some examples would be:
•Size
•Shape
•Color
The Punnett Square
●
Is a square grid used in genetics to calculate the
frequencies of the different genotypes and phenotypes
among the offspring of a cross
Alleles on homologous chromosomes
●
These alternative forms of a gene that code for a trait are called
alleles. There are 2 alleles for each trait; 1 allele for a trait is from
mom and 1 allele is from dad.
Homologous Chromosomes
Principle of Dominance
• Dominant allele (capital letter) masks the expression of
the recessive allele (lower-case)
• Alleles occur on a homologous pair of chromosomes at a
particular gene locus (location of gene on the
chromosome)
•
Homozygous = identical alleles (TT, tt)
•
Heterozygous = different alleles (Tt)
Figure 14.2
TECHNIQUE
1
2
Parental
generation
(P)
3
Stamens
Carpel
4
RESULTS
First filial
generation
offspring
(F1)
5
Genotype Vs. Phenotype
• Genotype
•
•
Refers to the alleles an individual receives at
fertilization
If alleles are identical, genotype is homozygous
If alleles are different, genotype is heterozygous
• Phenotype
•
•
Refers to the physical appearance of the
individual
Law of Segregation
•
•
•
•
•
Each individual has two factors for each trait
The factors segregate during gamete
formation
Each gamete contains only one factor from
each pair of factors
Fertilization gives each new individual two
factors for each trait
This law is also referred to as law of purity of
gametes.
Figure 14.5-3
P Generation
Appearance:
Purple flowers White flowers
Genetic makeup:
pp
PP
p
Gametes:
P
F1 Generation
Appearance:
Genetic makeup:
Gametes:
F2 Generation
Purple flowers
Pp
1/
1/
2 p
2 P
Sperm from F1 (Pp) plant
p
P
Eggs from
F1 (Pp) plant
P
p
3
PP
Pp
Pp
pp
:1
Figure 14.6
3
Phenotype
Genotype
Purple
PP
(homozygous)
Purple
Pp
(heterozygous)
1
2
1
Purple
Pp
(heterozygous)
White
pp
(homozygous)
Ratio 3:1
Ratio 1:2:1
1
Law of Independent Assortment
●
●
Pairs of alleles for different traits separate independently
of one another during gamete formation (meiosis).
In other words the inheritance of one trait has no
influence on the inheritance of another trait.
Figure 14.8
EXPERIMENT
YYRR
P Generation
yyrr
yr
Gametes YR
F1 Generation
YyRr
Hypothesis of
dependent assortment
Predictions
Hypothesis of
independent assortment
or
Predicted
offspring of
F2 generation
Sperm
1/
1/ YR
2 yr
2
1/
2
YR
1/
2
YyRr
YYRR
Eggs
1/
1/
4
YR
1/
4
Yr
1/
4
yR
1/
4
yr
Eggs
yr
YyRr
3/
yyrr
1/
4
4
Phenotypic ratio 3:1
9/
16
4
YR
1/
4
Sperm
Yr 1/4 yR
1/
4
yr
YYRR
YYRr
YyRR
YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR
YyRr
yyRR
yyRr
YyRr
Yyrr
yyRr
yyrr
3/
16
3/
16
1/
16
Phenotypic ratio 9:3:3:1
RESULTS
315
108
101
32
Phenotypic ratio approximately 9:3:3:1
THANKS!
Patterns of inheritance of characters
and principles of heredity.
Checked by: Blyalova J. J.
Prepared
by: Maratova Ayaulym,
CREDITS: This presentation template was created by Slidesgo,
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includingKuralay
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Group: HB-31