Heredity Reproduction 6th Grade Chapter 4 Review Mrs Nell Heredity Heredity is the passing on of traits from parents to offspring In this family tree t

							Heredity & Reproduction


   6th Grade
Chapter 4 Review
   Mrs. Nell
                        Heredity

Heredity is the passing on
of traits from parents to
offspring. In this family
tree, traits such as hair color
and poor eyesight are
passed from generation to
generation.
                          DNA
Chromosomes contain genes and
are made up of DNA. Genes are
small sections of chromosomes that
determine traits (physical
characteristics of an organism).
DNA is inside the nucleus of cells
and carries the genetic information.
This information is passed on from
parent to offspring.
The scientific name for DNA is
deoxyribonucleic acid.
                    Alleles
The different forms that a
gene may have for a trait
are called alleles. For
instance, in pea plants
flowers may be purple or
white. Purple is dominant.
Dominance is when one
trait covers over or masks
another form of the trait.
White is recessive. A trait
that is hidden or masked if
the dominant form of the
trait is present is called a
recessive trait.
Dominant vs. Recessive
 In humans, brown eye color is the dominant
 trait, whereas non-brown eye color is the
 recessive trait.
                       Pure
When an organism has two
identical alleles for a trait, it
is said to be a pure bred (ex-
2 purple flower alleles).
When an organism contains
different alleles for a trait it is
said to be a hybrid (ex- 1
purple and 1 white flower
allele).
 Multiple Alleles & Genes
Some traits in organisms, like blood typing, are
controlled by more than two alleles.




Other traits are controlled by more than one gene
(like height, weight, eye, skin, and hair color).
          Reproduction
Reproduction is the process by which organisms
make more of their own kind. Asexual
reproduction is a method of reproduction in
which one organism produces a new organism.

Yeast
budding
                   Hydra     Budding is a form of
                   budding
                             asexual reproduction
                             when an offspring
                             grows off of the
                             parent organism.
                  Regeneration
  Regeneration is a form of asexual
  reproduction when missing parts grow back
  or a whole organism forms from a piece of
  the parent organism.




Starfish, sponges, and planaria are a few organisms that can regenerate.
   Sexual Reproduction
In sexual reproduction, a new cell is
produced when DNA from both parents
combine.
                Embryo
• An embryo is a fertilized egg that has
  begun dividing into more cells.
                       Cloning
Cloning is the creation of an organism
that is an exact genetic copy of another.
This means that the DNA is identical to
another organism.

In 1997 scientists successfully cloned a
sheep named Dolly. Dolly was the first
cloned mammal. In 2003, a decision
was taken to "euthanize" six-year-old
Dolly after a veterinary examination
showed that she had a progressive lung
disease.
            Benefits of Cloning
•   Agriculture: Farmers and ranchers can have their strongest crops and
    animals twinned so that they are less likely to contract diseases.
•   Transplants: Pig hearts are often used as transplants to replace
    diseased human hearts.
•   Knowledge of Cells: Learning how cells become specialized could
    benefit people with diseases such as diabetes or could help those with
    spinal cord injuries walk again.
                Cloning Today
Since Dolly’s creation, scientists have
cloned many other mammal species --
cattle, pigs, cats, rabbits, dogs, and
even horses. Still, researchers are far
from mastering the cloning process.
Attempts to clone animals have
resulted in numerous losses and
abnormalities. More study,
experimentation, and technological
advancements are needed.                  The female foal, dubbed
                                          Prometea, is actually a clone of
                                          the mare that gave birth to it.
           Cell Division
All cell division is not the
same. Cells can divide by
mitosis, so each daughter
cell retains a full set of
chromosomes, or by
meiosis, which halves the
chromosomes and
produces sperm and eggs.
               Mitosis
Mitosis is the process when the nuclei of
body cells split. This produces two nuclei
with the exact same information.
  Mitosis (Stage 1: Prophase)
• Chromosomes become visible
• Nuclear membrane breaks down
• Spindle fibers form at opposite "poles" of the cell
Mitosis (Stage 2: Metaphase)
• The nuclear membrane disappears completely
• Chromosomes line up near the center of the cell
Mitosis (Stage 3: Anaphase)
• Paired chromosomes separate and
  move to opposite ends (poles) of the
  cell
Mitosis (Stage 4: Telophase)
• Two separate groups of chromosomes at each
  pole
• A nuclear membrane begins to form around
  each set of chromosomes to form two nuclei
                 Meiosis
Meiosis is the process of sex
cell formation. Eggs are
female sex cells and sperm
are male sex cells.


Fertilization is the process in
which sperm and egg unite,
resulting in a new individual
with a full set of chromosomes.
                      Genetics
Genetics is the study of how traits are passed from parent to
offspring. Individual animals and plants differ from other
individuals of the same species in all sorts of ways, even when
they are offspring of the same parents. These differences between
individuals of the same species are called variations.
                                                 Height is a
                                                 variation
                 Mutations
Sometimes genes change by
mutation- a random mistake during
the copying of genetic material in
meiosis or mitosis. Mutations can
also occur due to environmental
factors (X-rays, dangerous
chemicals, etc.). Mutations are the
source of all genetic variation and
therefore the basis of evolutionary
change.                               Down's syndrome is caused by the
                                      presence of an extra chromosome in
                                      chromosome set 21.
          Gene Mutations
 In gene mutations a chemical change occurs in an
individual gene. Although this change may be very
small, it can cause abnormalities such as albinism.
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