Download Inheritance of Traits

Genetics
Vocabulary
• Heredity- the passing of traits from parent to offspring
• Gene- a section on a chromosome that has genetic information for one
trait
• Allele- different forms of a gene
• Traits- genetic factors
• Chromosomes-threadlike structures in the nucleus that contain genetic
information that controls traits
• DNA- an organism’s genetic material
• Dominant trait-genetic factor that blocks another genetic factor
• Recessive trait-genetic factor that is blocked by a dominant factor
• F1 Generation- first generation offspring
• P Generation- parent generation
• Genotype- alleles that control a phenotype
• Phenotype- how a trait appears
• Every organism requires a set of instructions
that specifies its traits. This hereditary
information (DNA) contains genes located in
the chromosomes of each cell. Heredity is the
passage of these instructions from one
generation to another.
Organization
Mendel and Laws of Heredity
• Gregor Mendel was the first to carry out
studies of heredity
• He studied height, flower color, seed coat
color
• He chose 1-2 traits per generation to watch
• He crossed plants with different traits and
learned that offspring usually had a dominant
trait
Mendel’s Discovery
• He found that the inheritance of traits
was not due to blending but instead
specific traits or units of inheritance were
passed from generation to generation
• Those units are called inheritance genes
Mendel’s Discovery cont.
• The second generation would show a
ratio of 3 to 1
• He deduced the presence of genes and
alleles
• Homozygous = same allele
• Heterozygous = different allele
Rule of Dominance
• Similar genes are arranged in a similar order in
a chromosome, the location on the
chromosome is called a locus
• Since 2 alternate forms are present we
describe them as follows
–Capital letters = dominant genes
–Lower case letter = recessive genes
• In a heterozygous pair, a dominant allele
masks the presence of a recessive allele
Punnett Squares
• Punnett squares were devised as a short-hand
way of finding expected outcomes of a cross
• Punnett squares can be used for monohybrid
crosses or dihybrid crosses
• Each parent has 2 alleles for each trait
• When gametes are produces, 50% have 1
allele for the trait and 50% have the other
Heterozygous X Heterozygous
Cross
Heterozygous X Homozygous
Cross
Homozygous X Homozygous
Cross
Patterns of Heredity and
Human Genetics
• Mendel’s theories can be used to explain
how human traits are passed from one
generation to the next
• Pedigrees are used to show the passing
of traits in humans
Pedigree Symbols
Example Pedigree
Pedigree Tracing Genetic Disorders