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GENETICS
Gregor Mendel
“Father of Genetics”
1822 - 1884
Mendel History
• Austrian Monk
• In 1856, 1st started
researching
inheritance of traits
• Studied pea plants
• Laws of Heredity
Mendel’s 7
traits studied
Pure Breeding Purple & White Flowers
1st Generation (F1)
2nd Generation (F2)
Mendel crossed a purple
flower with a white flower.
Mendel crossed 2 F1 purple
flowers.
Result: 4 purple flowers
Result: 3 purple flowers and
1 white flower (3:1 ratio)
Mendel’s Conclusions
• Organisms inherit 2 copies of each gene
• One from each parent
• Variations in traits caused by alternative
versions of genes called alleles.
• Expression of trait
• Dominant alleles trumps recessive alleles
Genetic Vocabulary
• Genetics - study of heredity
• Heredity - passing of traits from parent
to child
• Gene – piece of DNA that provides set
of instructions to make certain proteins
– Located on chromosome
– Inherited from mom and dad
– Come in different versions called
alleles
• Example: Flower color
White allele or Purple allele
• Example: Rolling Tongue
Can roll tongue or Can’t
Phenotype – appearance/expression of a trait
Genotype – genetic makeup of a specific set of genes, made up of alleles
Dominant allele – CAPTIAL LETTER (R)
Recessive allele – lower case letter (r)
Genotype
Phenotype
TYPES OF
GENOTYPES
HOMOZYGOUS
DOMINANT
HETEROZYGOUS
HOMOZYGOUS
RECESSIVE
Genetics Vocabulary Review
Choices:
1) YY
2) Tall
3) Yy
4) SS
5) yY
6) gg
7) Smooth
8) Green
9) TT
10) Dwarf
Which choice(s) are examples of:
Genotypes?
1, 3, 4, 5, 6, 9
Phenotypes?
2, 7, 8, 10
Homozygous genotypes?
1, 4, 6, 9
Heterozygous genotypes?
3, 5
Homozygous recessive genotypes?
6
Homozygous dominant genotypes?
1, 4, 9
Autosomal Inheritance
• Autosome: Non-sex
chromosome
• Autosomal disorders are
caused by genes found on
the non-sex chromosomes
– ex: Sickle cell =
chromosome #11
– ex: Cystic fibrosis =
chromosome #7
• Usually recessive
– Must inherit two
copies to be sick
Attached earlobes is a homozygous recessive trait (ee). Cross a person
who is homozygous dominant (no attached earlobes, EE) with a person
who has attached earlobes.
Probability offspring will have attached earlobes?
0%
Probability offspring will be homozygous dominant?
0%
Probabilitiy offspring will be heterozygous?
100%
Maria is a heterozygous healthy (Hh) female and Jeff
suffers from recessive cystic fibrosis (hh).
Key
H = healthy
h = cystic
fibrosis
Probability of having a healthy
50%
child? _________
Probability of having a homozygous
0%
dominant child? ________
Kobe Kuiz
1) How are dominant alleles expressed? Recessive?
2) Which of the following are genotypes? Phenotypes?
TT Green yY Pp Purple gg Smooth
3) Which of the following are heterozygous genotypes?
TT Green yY Pp Purple gg Smooth
4) Genes may often be found in two forms (dominant and recessive). What are
these alternate forms of a gene called?
5) Genes are segments of DNA found on _______________.
6) If item A is found in a 2:1 ratio compared to item B, what percentage is item A?
7) If item A is found in a 4:1 ratio compared to item B, what percentage is item A?
8) George & Martha are planning a family. Each has a family history of autosomal
recessive disorder and they agree to have their blood tested. George is found to
be heterozygous healthy and Martha is found to be homozygous dominant
healthy. What are the chances they have a healthy child? Homozygous dominant
child? Heterozygous child? Homozygous recessive child?