Chapter 8-extension (advanced notes on Mendelian Genetics)
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Transcript Chapter 8-extension (advanced notes on Mendelian Genetics)
Chapter 11 Notes
Introduction to Genetics
Genetics – Study of heredity
Heredity – How things or
characteristics (traits) are passed on
from parent to offspring
Gregor Mendel ( 1822-1884 )
1. “Father of Genetics”
2. Austrian Monk in the 1800’s –
worked with pea plants
3. Why garden peas?
- Reproduced by self-pollination
- Have seven different traits (ex.
Tall vs. short,
round vs. wrinkled)
4. His experiments led to 4 Laws
Fundamental Laws of Heredity
Law of Unit Characters
Traits are controlled by factors called genes
For every trait you have 2 genes
1 from each parent
Law of Dominance
One of the gene pair can mask the other
The gene which appears or does the
masking is called the dominant gene
The gene being masked is called recessive
Law of Segregation
- During the formation of gametes (meiosis)
each gamete only receives one gene from the
pair. (The chromatids separate and go to
separate cells)
Law of Independent Assortment
- Chance is involved in determining
which gene a gamete will receive
Genetic Terms and Abbreviations:
Dominant Gene – (the masker)
- Symbolized by a capital letter
Recessive Gene – (the masked)
- Symbolized by a small letter
Homozygous – Alleles/genes are the same
- Purebred (TT, tt)
Heterozygous – Alleles/genes are different
- Hybrid (Tt)
Genotype – The genetic make-up of an
individual
-Letters (TT, Tt, tt)
Phenotype – The individuals physical
appearance
- Words (tall, short, straight hair, green eyes, etc.)
Punnett Square – Resembles a checker board
and shows the possible gene combinations of
offspring
Abbreviations and Generations
P1 – Pure breeding parent generation
F1 – (1st Fillial) Offspring generation; cross
between members of the P generation
F2 – (2nd Fillial) Offspring of crosses
between members of F1 generation
Ratios for MONOHYBRID CROSSES
Phenotypic Ratio – Shows the ratio of physical
traits
How many dominant : How many recessive
Ex. 3 Tall : 1 Short
Genotypic Ratio – Shows the ratio of different
genotypes
Homozygous dominant: Heterozygous dominant: Homozygous recessive
Ex. 1TT : 2Tt : 1tt
Example Monohybrid Cross
In humans, being a tongue roller (R) is dominant over nonroller (r). A man who is a non-roller marries a woman who is
heterozygous for tongue rolling.
Father’s phenotype _____
Father’s genotype _____
Mother’s phenotype _____
Mother’s genotype _____
What is the probability of this couple having a child who is a
tongue roller? ________
Example Monohybrid Cross
In humans, being a tongue roller (R) is dominant over non-roller (r). A
man who is a non-roller marries a woman who is heterozygous for
tongue rolling.
Father’s phenotype :non-roller
Father’s genotype : rr
r
r
Mother’s phenotype: roller
Mother’s genotype : Rr
R
r
Rr
rr
Rr
rr
What is the probability of this couple having a child who is a tongue
roller? 2/4 = 50%