Download Genetics: The Science of Heredity

Chapter 4 Review
heredity—the passing of physical
characteristics from parents to
offspring
genetics—the science of heredity
trait—a biological characteristic
Dominant allele
 one whose trait
always shows up in
the organism when
the allele is present
Recessive allele
 Hidden whenever the
dominant allele is
present
 Only shows up when
if the organism does
not have the
dominant allele
 A chart that shows all the possible combinations of
alleles that can result in a genetic cross
Phenotype
 an organism’s physical
appearance
 Descriptive; will always
be given in words
 Ex.—curly hair,
smooth pods, spotted
egg shell
Genotype
 an organism’s genetic
makeup
 Will always will be
given in letters; allele
combinations
 Ex.—Gg, TT, DD, rr, Bb
Genotypes
can be either
homozygous
or
heterozygous
 Fertilization—process that occurs when egg and
sperm cells join to form a new organism
 Sex cells have half the number of chromosomes as
does body cells.
 The chromosome theory of inheritance states that
genes are carried from parents to their offspring
on chromosomes.
 During meiosis, the chromosome
pairs separate and are distributed
to two different cells.
 The resulting sex cells have only
half as many chromosomes as the
other cells in the organism.
*genotype
*phenotype
*heredity
*Punnett square
*meiosis
*allele
*gene
*genetics
*homozygous
*heterozygous
*fertilization
*trait
*chromosome
*recessive allele
*dominant allele
Chromosomes
are made up of
many genes
joined together
like beads on a
string.