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Heredity
By: Mr. Hunter
Heredity
Heredity is the
passing of genetic
traits from parent to
offspring.
Why is
Gregor Mendel
important?
Gregor Mendel
 Naturalist
 Grew
up on a
farm and
learned a lot
about flowers
and fruit trees
Gregor Mendel

Mendel was brilliant, but had difficulty
understanding written texts.

He explored the scientific ideas he had
trouble with and became known as the “father
of modern genetics.”
Mendel’s pea plants
 What
does self-pollination
mean?
 Why
are self-pollinating flowers
excellent for scientific study?
 What
is cross-pollination?
How did Mendel use
the scientific
method?
Mendel used the scientific
method!

Ask a question: How are traits inherited?

Form a hypothesis: Inheritance has a
pattern.

Test the hypothesis: Cross true-breeding
plants and offspring.
Mendel/Scientific Method

Analyze the results: Identify patterns in
inherited traits.

Draw conclusions: Traits are inherited in
predictable patterns
Mendel
Dominant/Recessive

Dominant: the trait observed in the first
generation when parents that have different
traits are bred

Recessive: a trait that reappears in the
second generation when parents with
different traits are bred
Mendel’s Second Go-Around
 During
his second set of
experiments, Mendel allowed
the first-generation plants,
which resulted from his first set
of experiments to self-pollinate
and the recessive trait
appeared.
Words (4 Square)
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Genes
Phenotype
Genotype
Allele
First Filial (F1)
Offspring
Dominant
Recessive
Punnett Squares
Heterozygous
Homozygous
What the heck?

In 1918, a prominent scientist miscounted the
number of chromosomes in a human cell. He
counted 48.

It was not until 1956 that the correct number
of chromosomes was found!
How are egg and sperm cells
different?

Egg and sperm cells have only 23 chromosomes.

All other cells have 46 chromosomes, or 2 pairs of
23.

Each pair is called homologous chromosomes.
Homologous Chromosomes

Chromosomes that have the same sequence
of genes and the same structure
Mitosis


Making two identical
cells
Happens in every cell
except _____ and
_____ cells
Phase
Description
Mitosis
Interphase:
Chromosomes are copied (# doubles)
Chromosomes appear as threadlike coils
(chromatin) at the start, but each
chromosome and its copy are known as
sister chromatids



Mitosis


Prophase
Centrioles (or poles) appear and begin to
move to opposite ends of cell
Spindle fibers form between the poles
Mitosis

Metaphase: Chromatids (or pairs of
chromosomes) attach to the spindle fibers
and move to the middle of the cell in a line
Mitosis

Anaphase:Chromatids (or pairs of
chromosomes) separate and begin to move
to opposite ends of the cell
Mitosis


Telophase:• Two new nuclei form
Chromosomes appear as chromatin (threads
rather than rods)
Mitosis

Cytokinesis:• Cell membrane moves inward
to create two daughter cells - each with its
own nucleus with identical chromosomes
Mitosis
Mitosis vs. Meiosis
_____ is when cells divide
and form four cells with
____ the number of
chromosomes as the
original cell.
Meiosis

This type of cell division happens only in
_____ and _____ cells.
Meiosis

Interphase I ->
 Prophase I (different from mitosis– DNA IS
SWAPPED!!!!!!!!! This is called _____ ).
Metaphase I -> Anaphase I -> Telophase I
-> Cytokinesis
THEN…
Prophase II -> Metaphase II -> Anaphase
II -> Telophase II -> FOUR CELLS
Mitosis
Meiosis
Heredity

There is always a 50% chance that a mother
and father will have a male child.

There is always a 50% chance that a mother
and father will have a female child.

Illustrate this with a Punnett Square.
Heredity

1. Why are men more likely to have sexlinked disorders?

2. Describe hemophilia in chromosomes.
Selective Breeding


This process of selecting parents is called artificial
selection or selective breeding, and poses no threat
to nature from man manipulating the course of
nature.
It has allowed our species to increase the efficiency
of the animals and plants we breed, such as
increasing milk yield from cows by continuously
breeding selected cows with one another to produce
a hybrid.