Fundamentals of
Genetics
Chapter 9
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Genetics: The Role of Genes in Inheritance and Development, Schemes and Mind Maps of Genetics
An overview of genetics, focusing on the essential role of genes in providing continuity between generations and controlling the structure, function, and development of organisms. It introduces Mendelian genetics, the discoveries of Gregor Mendel, and the concepts of dominant and recessive genes, alleles, genotypes, and phenotypes. The document also covers the laws of segregation and independent assortment, monohybrid and dihybrid crosses, and various examples of gene expression in pea plants, guinea pigs, fruit flies, and summer squash.
Typology: Schemes and Mind Maps
2021/2022
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Fundamentals of
Genetics
Chapter 9
M
d li
G
ti
M
endelian Genetics
Gregor MendelGregor
Mendel
•^
Trained mathematician & natural scientist whodiscovered the basicrules of heredityrules of heredity
-^
Interested in theinheritance of animal & plant features --- traitsor characteristics
Hybrid
: offspring expressing traits from both
parents
•^
He chose strains that showed 2 different forms of thesame trait.same trait.
ex:
length - tall/short
green/yellow seed color
•^
Worked with 7 different traits in pea plants: a. seed shape – round, wrinkledb. seed color – yellow, green c. flower color – colored, whited. pod shape – inflated, constricted
d^
l^
ll
e. pod color – green, yellowf. flower position – axial, terminalg stem length – long shortg. stem length – long, short
•^
In his 1
st^ experiment, he crossed pure-breeding
p^
,^
p^
g
plants round seeds with pure-breeding wrinkledseeds
P^1
= Parental generation All were round seeds
In his 2
nd^
experiment, he allowed these seeds to grow &
self-pollinate
F^1
= Filial Generation
¾ round (75%)
¼ wrinkled (25%)
ChromosomesChromosomes
GENES
Sex cell
Body cell
2 types of GENES:
d^
i^
t^
ti^
t^
lli
dominant:
exerting a controlling
influence on the expression of a trait.
recessive:
the one that disappears
temporarily.
Dominant
Recessive
-^
Assigned symbols to different genesAssigned
symbols to different genes
ex: R – dominant gene (round)ex: R – dominant gene (round)
r – recessive gene (wrinkled)
Alleles
: the 2 different forms of one gene
R & r
RR
purebreed for round
RR – purebreed for roundrr – purebreed for wrinkled
Mendel
’s Laws
Mendel s Laws
Law of Segregation: a pair of factors is segregated, or
g^
g^
p^
g^
g^
separated, during the formation of gametes.Each gamete receives one trait for each pair. Law of Independent Assortment: factors separateLaw of Independent Assortment: factors separate
independently of one another during the formation ofgametes.
PUNNETT SQUARESPUNNETT
SQUARES
A way to show which genes can combineA way to show which genes can combine
when egg and sperm join.
capital letter
Dominant
capital letter
lower case
l^
b^
f^
F
Dominant Recessive
ex: earlobes
freeattached
F f
FF Ff
Pure Dominant FreeHeterozygous Free
Ff ff
Heterozygous FreePure Recessive Attached
To Determine Possible
C
bi
i
Combinations:
- Set up the key. 2. Determine the cross.3. Draw a Punnett Square.3. Draw a Punnett Square.
4. Decide what kind of genes will be in the sexcells of each parent
Write the letters for the
cells of each parent. Write the letters for thefather on top.
FF
x
FF
FF
x
FF
F^
F