Chapter 3 Reproduction and Heredity
Lesson 1 Reproduction and Growth continued
To reproduce is to make more of one’s own kind.
 Living things pass their genetic traits to
offspring in one of two ways:
asexual reproduction or sexual reproduction
Asexual Reproduction- only one parent
produces an offspring
Examples:
1.
Fission- one cell divides to form two
identical cells just like the parent. Ex. Bacteria
2.
Budding- parent grows a small bud. The
bud breaks off to form a new organism. Ex.
Hydra
3.
Runners or shoots- some plants send out
runners or shoots which new plants form on
the ends. Ex. Spider plant, grasses
Sexual Reproduction- two parents produce
offspring that inherit traits from each one
 Each organism gets a unique combination of
traits
 Gametes- specialized reproductive cells:
Female gamete – egg, Male gamete- sperm
 Fertilization- the union of egg and sperm to
form a new cell which forms into a new
organism
Lesson 1 Reproduction and Growth continued
 Cells contain genetic information and when
they divide they pass the genetic plan for the
entire organism to the new cells.
 Different parts of the plan are expressed in
different cells.
 Genetic information- in nucleus in
chromosomes in molecules called DNA
The Cell Cycle
All body cells grow and divide in a regular cycle.
1.
Interphase- longest phase where cell
grows and makes a copy of its chromosomes.
2.
Mitosis- the division of the nucleus.
Organizes chromosomes into two nuclei. Each
nucleus gets one copy of each chromosome.
3.
Cytokinesis- cell wall or cell membrane
divides the two new cells. New cells are on
their own.
Genetic Traits
Traits are characteristics of living things and traits
that genes control are called genetic traits. For
example: eye color, hair color, height
 Chromosomes come in pairs.
 Each member of the pair has genes from one
parent- one came from mom the other from
dad.
 Dominant traits are always expressed.
 Recessive traits only appear when a
dominant trait is not present.
 Selective breeding- two individuals with
desired traits form an offspring. For example:
sheep are bred to produce wool that is easier
to spin into yarn, plants are bred to yield
bigger crops.
Lesson 2 Inherited Traits
Gregor Mendel- father of the science of genetics
-worked with pea plants
Allele- different forms of gene for a trait
For example: Trait: height
Allele 1- tallness
Allele 2- shortness
Dominant allele- an allele that is always
expressed and will cover up a recessive allele
(tallness)
 Written as a capital letter
Recessive allele- an allele that will only be
expressed if a dominant allele is not present
(shortness)
 Written as a lower case letter
Purebred- has two of the same allele for a trait
Hybrid- the offspring of two parents from
different purebred strains
For example: Tall Tall is bred with short short
TT
x
tt
Tt- hybrid offspring
Lesson 2 Inherited Traits continued
Punnett Square – a way to help researchers
predict the results of genetic crossings
Codominant- when two dominant alleles are
both expressed. For example: a chicken offspring
with black and white feathers.
Incomplete dominance- when a dominant allele
is partly expressed. For example: four o’clock
flower is pink and not the dominant color red.
Meiosis- the process that produces gametes. The
number of chromosomes is reduced by half to a
total of 23.
DNA- deoxyribonucleic acid. It is the genetic
material for all living things.
Lesson 3 Transferring Genetic Information
DNA has the shape of a double helix, or a spiral
staircase or twisted ladder.
The sides are made up of sugars and phosphates.
The rungs are made up of base pairs.
Only four different bases:
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
A always pairs with T and G always pairs with C.
Lesson 3 Transferring Genetic Information
continued…
An important property of DNA is that it can
replicate, or make copies of itself.
DNA stores information about cell structure and
function. In order for these instructions to be
carried out, the DNA must be transcribed, or
decoded into RNA.
RNA- ribonucleic acid, is used to make proteins.
Proteins determine the structures of a cell and the
functions they perform. Insulin is a protein that
helps regulate the level of sugar in the blood.
Two types of RNA:
mRNA- messenger RNA, carries genetic
information to the ribosomes
tRNA- transfer RNA, carries amino acids to
ribosomes. Amino acids are the building blocks of
proteins and are need to make them.
Proteins are made in the ribosomes.
Mutation- any permanent change in a gene or a
chromosome. For example, sickle cell anemia.