51 Heredity

1
5-1 Heredity
2
Heredity is the passing of traits from parent to
offspring.
3
Alleles are the traits that a gene carries.
4
Genetics is the study of heredity, or the passing
of traits from parents to offspring.
5
Gregor Mendel-Lived in the mid 1800s. He is
called the father of genetics because of his
early work in genetics.
6
Mendel worked with pea plants. He studied the
traits that cause a plant to be tall or short. He
performed a lot of experiments.
7
The first step in Mendels experiment was the
crosspollination of short pea plants with short
pea plants. All of the offspring were short pea
plants.
8
Mendel called these plants true-breeding plants
because they always produced short plants. They
became known as pure-bred plants.
9
Mendel repeated the experiment with tall plants.
He found out that not all tall plants would
produce tall offspring.
10
The second step was the crosspollination of a
tall and a short pea plant. All of the offspring
were tall.
11
The third step was the self-pollination of tall
plants. This produced some tall and some short
plants.
12
Mendel discovered that some tall plants pure-bred
plants and some were not. He called these plants
hybrids.
13
Mendel called the trait that could be seen
dominant traits (alleles) and the ones that were
hidden recessive traits (alleles).
14
Some alleles are dominant, where as other alleles
are recessive.
15
Dominant alleles hide recessive alleles when both
are inherited by an organism.
16
Probability-The likely hood that something will
happen.
17
Scientist use a Punnett Square to calculate the
probability of receiving inherited traits.
18
Purebred-When an organism contains the same
allele for a trait (BB, bb).
19
Hybrid-When an organism has different allele for
a trait (Bb).
20
Phenotype-A visible, physical, characteristic.
What it looks like (color, height, etc.).
21
Genotype-The actual gene make-up of an organism (
Bb, BB, bb).
22
Homozygous-An organism that has two of the same
alleles for a trait (TT, tt).
23
Heterozygous-An organism that different alleles
for a trait (Tt).
24
Punnett Square-It is a method of calculating the
probability of inheriting a certain trait.
25
1st step-Place the genotype of the first parent
on the top of the Punnett Square, one on each
box.
B b
Blond bb Black BB Black is dominant over
blond.
26
2nd Step-Place the genotype of the 2nd parent on
the side of the Punnett Square.
B b
Brown bb Black BB Black is dominant over
blond.
b b
27
3rd Step-Multiply the top row (genes of 1st
parent) by the 1st gene of the 2nd parent (always
place capital letter first).
B b
Brown bb Black BB Black is dominant over
blond.
b b
Bb bb
28
4th Step-Multiply the top row (genes of 1st
parent) by the 2nd gene of the 2nd parent.
B b
Brown bb Black BB Black is dominant over
blond.
b b
Bb bb
Bb bb
29
Final step-Decide the phenotypes of the
offspring. Remember the dominant gene is the gene
that will show.
B b
Brown bb Black BB Black is dominant over
blond.
b b
Bb bb
Bb bb