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Genetics
the study of inheritance
There are 2 types of cell
division:
● Mitosis- growth and repair involved in cells
replicating themselves and all of their DNA into
exact copies of original cells
● Meiosis- sexual reproduction combining sperm &
egg to produce an new and original organism that
has half of it’s DNA from each parent into a original
and unique combination of traits
Gregor Mendel
http://science.discovery.com/tv-shows/greatest-discoveries/videos/100-greatestdiscoveries-shorts-genetics.htm
• Father of Genetics
• Austrian monk
• discovered heredity principles
• studied pea plants
What Is Heredity?
Crossing Pea Plants
Mendel devised a way to cross-pollinate pea plants.
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Common traits Mendel
identified in Pea Plants:
seed shape- round vs. wrinkled
seed color-yellow vs. green
pod shape-pinched vs. smooth
pod color-green vs. yellow
flower color-purple vs. white
flower position-top of stem vs. side of stem
stem height- tall vs. short
What Is Heredity?
Alleles in Pea Plants
Mendel studied the inheritance of seven different traits in pea plants.
What Is Heredity?
Results of a Cross
In Mendel’s crosses, some forms of a trait were hidden in one
generation but reappeared in the next. What was surprising about the
offspring in the F2 generation?
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asexual reproduction
sexual reproduction
heredity
trait
genetics
purebred
parental P1 generation
First filial F1 generation
Second filial F2 generation
offspring
gene
allele
dominant
recessive
hybrid
probability
Punnett square
phenotype
genotype
homozygous
heterozygous
Sample Crosses
If a purebred tall pea plant with was cross
pollinated with a purebred short pea plant
describe it's offspring:
Parent (P) GenerationFirst Filial (F1) GenerationSecond Filial (F2) Generation-
Sample Crosses Part 2
If a purebred pea plant with purple flowers
was cross pollinated with a purebred pea
plant with white flowers describe it's
offspring in each:
Parent (P) GenerationFirst Filial (F1) Generation-
Second Filial (F2) Generation-
Sample Crosses Part 3
If a purebred pea plant with wrinkled seeds
was cross pollinated with a purebred pea
plant with round seeds describe it's
offspring in each:
Parent (P) GenerationFirst Filial (F1) GenerationSecond Filial (F2) Generation-
A GREAT visual
representation!
http://www.doctortee.com/dsu/tiftickjian/genetics/mendels-experiments.html
Probability and Heredity
How to Make a Punnett Square
What are the steps in using
a Punnett Square to find the
probabilities of a genetic cross?
Probability and Heredity
Describing Inheritance
An organism’s phenotype is its physical appearance. Its genotype is its
genetic makeup. Complete the missing information in the table.
Punnett squares
Punnett Square-draw, label & complete
A homozygous pea plant with yellow seeds is crossed with a homozygous pea plant
with green seeds.
y
y
Y
Y
Describe the results in: percentages, ratios and fractions & use the terms heterozygous and
homozygous in your results
Phenotypes of each plant:
Genotype of each plant
Punnett Square- Draw, label & complete
A heterozygous pea plant is crossed with another heterozygous pea plant with both
with yellow seeds.
Y
y
Y
y
Describe the results in: percentages, ratios and fractions & use the terms heterozygous and
homozygous in your results
Phenotypes of each plant:
Genotype of each plant
Punnett Square Practice:
For each sample question fill in the Punnett square and describe the offspring in the F1 generation. Include:
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Genotypes (Percentages, ratios, fractions of alleles)
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Phenotypes (Percentages, ratios, fractions of each physical appearance)
Sample #1: In Guinea pigs black fur color is dominant over white fur color. Suppose a
homozygous black male guinea pig mated with a heterozygous black female guinea pig.
(P) Parent Alleles:
F1 Generation:
Sample #2: In Guinea pigs Smooth fur is dominant over Cow licked fur. Suppose a heterozygous
smooth male guinea pig mated with a homozygous cow licked female guinea pig.
(P) Parent Alleles:
F1 Generation:
Sample #3: In Guinea pigs Solid fur color is dominant over Calico fur color. Suppose a
homozygous Solid male guinea pig mated with a Calico female guinea pig.
(P) Parent Alleles:
F1 Generation:
Dihybrid crosses
Sample #4: In Guinea pigs Black fur color is dominant over White fur color & Solid fur
color is dominant over Calico fur color. Suppose a homozygous Solid black male guinea
pig mated with a heterozygous Calico black female guinea pig. What would the offspring
be like?
(P) Parent Alleles:
F1 Generation:
Sample #5: In Guinea pigs Smooth fur is dominant over Cow licked fur and Black fur
color is dominant over white fur color. Suppose a heterozygous Black & Smooth haired
Male mated with a White & Cow licked haired female guinea pig. What would the
offspring be like?
(P) Parent Alleles:
F1 Generation:
Sample #6: In Guinea pigs Black fur color is dominant over White fur color & Solid fur
color is dominant over Calico fur color. Suppose a heterozygous Solid black male guinea
pig mated with a homozygous Calico black female guinea pig. What would the offspring
be like?
DiHYbrid Crosses
http://www.biology.arizona.edu/mendelian_g
enetics/problem_sets/dihybrid_cross/03t.html
Vocabulary/Terms List Part 2:
• Mendel’s experiments with pea plants led to an understanding of
how traits are controlled by genes. However, some traits are not
controlled by genes with only 2 possible alleles.
There are 4 other complex patterns of inheritance: Give an
explanation of each below: Include examples!!!
o Incomplete dominanceo Codominanceo Multiple alleleso Polygenic inheritanceDefine: Meiosis-
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What does the chromosome theory of inheritance state?
Compare and Contrast the processes of Mitosis and Meiosis: be sure to
include when/what each is used for and in what types of cells
https://www.youtube.com/watch?v=zGVBAHAsjJM
Patterns of Inheritance
Blingwings
An imaginary insect called
the blingwing has three
alleles for wing color: R
(red), B (blue), and Y
(yellow).
1. What are the 6 possible
allele pairs that can be
inherited?
2. Suppose the 3 alleles are
codominant, what wing color
would each pair of alleles
produce?
Nature:
DNA, Genes and Chromosomes
• Genes make you who
you are.
Genes hold the key to heredity
• A gene is a short segment of DNA that
contains the instructions for how to make
one (or more) proteins.
• Each protein carries out a specific function
within our body.
MS, HS – LS3A
Chromosomes and Inheritance
Paired Up
Sutton studied
grasshopper
cells through a
microscope. He
concluded that genes are
carried on
chromosomes.
Chromosomes and Inheritance
A Pair of Chromosomes
Chromosomes in a pair
may have different alleles
for some genes and the
same alleles
for others. Is the organism
homozygous or
heterozygous?
Chromosomes and Inheritance
Meiosis
During meiosis, a cell produces sex
cells with half the number of
chromosomes. The correct number
is restored when sperm and eggs
combine!