Nick Mason
#19
10/16/10
Science 8
Chapter 5
heredity
Heredity is the passing of physical characteristics from parents to
offspring.
trait
Each different form of a characteristic such as, seed color or height,
is called trait.
Genetics
The scientific study of heredity is called genetics.
fertilization
A new organism begins to form when egg and sperm join in the
process called fertilization.
purebred
A purebred organism is the offspring of many generations that have
the same trait.
gene
Scientists use the word gene for the factors that control a trait.
alleles
Alleles are the different forms of a gene.
dominant allele
A dominant allele is one whose trait will always show up in the
organism when the allele is present.
recessive allele
A recessive allele is hidden when the dominant allele is present.
Nick Mason
#19
10/16/10
Science 8
hybrid
A hybrid organism has two different alleles for a trait.
probability
Probability is a number that describes how likely it is that a certain
event will occur.
Punnett square
A Punnett square is a chart that shows all the possible combinations
of alleles that can result from a genetic cross.
Phenotype
An organism’s phenotype is its physical appearance, or visible traits.
genotype
An organism’s genotype is its genetic makeup, or allele
combinations.
homozygous
An organism that has two identical alleles for a trait is said to be
homozygous.
heterozygous
An organism that has two different alleles for a trait is heterozygous.
codominance
In codominance, the alleles are neither dominant nor recessive. As
a result, both alleles are expressed in the offspring.
Nick Mason
#19
10/16/10
Science 8
sexual reproduction
In sexual reproduction, genetic material from two parents combines
to produce a new organism, which differs from both parents.
diploid
A diploid is a cell that contains two sets of chromosomes, one set
from each parent.
meiosis
Meiosis is the process by which the number of chromosomes is
reduced by half to form sex cells – sperm and eggs.
messenger RNA
Messenger RNA copies coded messages from the DNA in the
nucleus and carries the message to the ribosome in the cytoplasm.
transfer RNA
Transfer RNA carries amino acids to the ribosome and adds them to
the growing protein.
mutation
A mutation is any change in a gene or a chromosome. Mutations
can cause a cell to produce an incorrect protein during
photosynthesis. As a result, the organism’s trait, or phenotype, may
be different from what it normally would have been.
MLA
Focus on California Life Science
Copyright 2008
Padilla, Miaoulis, Cyr
Nick Mason
#19
10/16/10
Science 8