Transcript Ch. 12 Genetics

Ch. 12 Genetics
A. Gregor Mendel (1822-1884) –
The father of Genetics

Mendel discovered the basic
principles of heredity by
breeding garden peas in
carefully planned
experiments.

Mendel defined different types of
hybridization
1. P generation – parental; true
breeding parents
2. F1 generation – 1st generation of
offspring
3. F2 generation – 2nd generation of
offspring
Trait
Form of ripe seed (R)
Color of seed
albumen (Y)
Color of flower (P)
Form of ripe pods (I)
Dominant
Expression
Smooth
Recessive
Expression
Wrinkled
Yellow
Green
Purple
White
Inflated
Constricted
Principles of genetics
 Traits are handed down from one
generation to the next
 Traits are controlled by genes
 Genes are inherited in pairs, one from
each parent

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Some genes are dominant some are
recessive
Dominant genes can mask recessive genes
when one of each is inherited
Some genes are not dominant or
recessive but blend when inherited
together
B. Genetic Vocabulary
1. Chromosomes: hereditary
units of an organism
2. Allele – One gene of gene pair for a trait.
for example: In the gene pair Bb for hair, color both B
& b are alleles
3. Homozygous – pair of BB = Brown
identical alleles for a character
4. Heterozygous – having 2 different
alleles for a character.
Bb = Brown
5. Haploid = contains one copy of each
chromosome (meiosis)
6. Diploid = contains two copies of each
chromosome (mitosis)
7. Genotype – an organism’s genetic
makeup.
BB or Bb
8. Phenotype – an organism’s outward
appearance.
Brown eyes
9. Mutations: changes in genetic material
10. Karyotype: an enlarged photograph of
the chromosomes in an organism
Above is a karyotype of a normal human male.
11. Multiple alleles - when more than 2
alleles control a trait. Example human
blood. A dominant, B dominant, O
recessive
Phenotype ( blood group)
Genotype
A
AA or Ao
B
BB or Bo
AB
AB or ABo
o
oo
12. Sex linked traits - gene for a trait is
carried on one of the sex chromosomes.
example color blindness, hemophilia
XX- Female
XY - Male
13. Meiosis - production of gametes
(sperm or egg cells) which contain half the
normal number of chromosomes
C. Ways to determine inherited
traits - Predicting traits
1.
Punnett square – a square used to
show all the possible combinations of
gametes.
A homozygous brown–eyed mother mates with a
blue – eyed father. What ratio of brown–eyed to
blue–eyed children will they have?
Brown eyes is the dominant trait
B- brown eyes
BB x bb
b- blue eyes
B
B
B
b
Bb
Bb
B BB Bb
b
Bb
Bb
b Bb
genotypic ratio is:
b
bb
100 % Bb
phenotypic ratio is: 100 % Brown
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2. Determining parental genotypes
Pedigree
Test – Test in which you
look at the offspring of parents to
determine the genotypes of the parents.
The
squares are for males and the
circles are for females.
If
the symbol has been darkened it
says the person carries the trait.