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REPRODUCTION
CHAPTER 3
TRAITS
• Heredity is the passing of traits from parents to
offspring.
• What are traits?
ASEXUAL REPRODUCTION
• Asexual Reproduction – A new organism or
cell is produced from one organism or cell
– Because there is only one parent, the offspring will
be genetically identical to the parent
– The offspring will have all the same traits as the
parent
TYPES OF ASEXUAL REPRODUCTION
Fission
• Parent cell splits in
two
• Very fast, can take as
little as 20 minutes
TYPES OF ASEXUAL REPRODUCTION
Forming Spores
• Spores can develop
into new organism
with the same DNA
TYPES OF ASEXUAL REPRODUCTION
Budding
During budding, the
organism grows a “bud”
on a part of it by mitosis.
When the bud grows large
enough, it breaks off and
lives on its own.
TYPES OF ASEXUAL REPRODUCTION
Regeneration
Regeneration is the process
that uses mitosis to regrow
body parts.
Some organisms will only
regrow the body part that was
severed.
In some organisms, the
severed part will become its
own separate organism
HOW ARE TRAITS PASSED ON?
CHAPTER 3, LESSON 2
DNA
• The instructions for an
organism’s traits can be
found in it’s DNA
• The structure of DNA
makes it possible for
organisms to pass traits
to their offspring
GENES
• A gene is a series of
base pairs
• The number of base
pairs varies from gene
to gene
DNA NITROGENOUS BASES PAIRING
• Nitrogenous bases in DNA always
pair up in a specific pattern
• Adenine (A) always pairs up with
Thymine (T)
• Cytosine (C) always pairs up
with Guanine (G)
A->T
C-> G
SEXUAL REPRODUCTION
CHAPTER 3, LESSON 3
MITOSIS VS. MEIOSIS
• Meiosis is the formation of sex
cells
– Mitosis is asexual reproduction
• Sex cells have half the number of
chromosomes of the parent cell
– Parent cells have chromosome
pairs, sex cells have single
chromosomes
• Meiosis results in 4 new cells
– Mitosis results in 2 new cells
• Meiosis has 2 cycles
– Mitosis has 1 cycle
FERTILIZATION IN FLOWERING PLANTS
• The stamen is the male
reproductive organ of flowers
• Produces pollen
• The pistil is the female
reproductive organ
• The ovary is the base of the
pistil
• Ovules are formed in the
ovary
FERTILIZATION IN ANIMALS
• Sperm cells contain unpaired chromosomes
• Egg cells contain unpaired chromosomes
• During fertilization, the sperm cell and egg cell
unite, and the DNA of the two cells combines
• The fertilized egg cell is called a zygote
INDIVIDUALS DIFFER
• Offspring produced by sexual
reproduction get half of their
chromosomes from their
mother and half from their
father, resulting in shared
characteristics from both
parents
– Offspring from asexual
reproduction have an exact
copy of the chromosomes
from the one parent cell
COMPARING SEXUAL AND ASEXUAL REPRODUCTION
ASEXUAL REPRODUCTION
•
•
•
•
Can happen quickly
Requires less energy
Needs just one parent cell
Produces offspring with
DNA identical to parent
SEXUAL REPRODUCTION
•
•
•
•
Is a slow process
Requires more energy
Must have two parent cells
Produces offspring with
unique DNA
HOW DO GENES DETERMINE
TRAITS?
CHAPTER 3, LESSON 4
DOMINANT AND RECESSIVE
• Genes work together to determine individual traits.
• Dominant Trait – A trait that will appear in the offspring
if one of the parents contributes it.
– In humans, dark hair is a dominant trait; if one parent
contributes a gene for dark hair and the other contrib
utes a gene for
light hair, the child will have dark hair.
DOMINANT AND RECESSIVE
• Recessive Trait – A trait that must be contributed by both
parents in order to appear in the offspring.
• Recessive traits can be carried in a person's genes
without appearing in that person.
– A dark-haired person may have one gene for dark hair,
which is a dominant trait, and one gene for light hair,
which is recessive.
– Because of this, it is possible for two dark-haired parents
to have a light-haired child
– Both parents would have had to pass on their recessive
gene to the child
SHARING DOMINANCE
• Not all genes follow the
dominant-recessive
pattern
• Some traits show both
versions of a gene at
work
– Erminette Chicken
– Four O’Clock Plants
SELECTIVE BREEDING
• Selective Breeding – Selecting a
few organisms with desired traits
to serve as parents of offspring
– Selective breeding has been
used for thousands of years
– Used in plants and animals to
get desired traits such as
better fruits and vegetables,
better/stronger animals, colors
of flowers, etc.