Genetics
Study of Inheritance
Reproduction
• Asexual
– Cell divides, creating an
identical daughter cell
• Sexual
– Exchange of genetic material,
both parents contribute to
fertilization of egg/ovary
– Increases diversity
– In Animals  Egg & Sperm
– In Plants  Pollen & Ovary
Heredity
• We share many similarities with our
parents & siblings, but we are not
genetically identical due to the mixing of
genes
Chromosomes
• A chromosome is a rod-shaped
bundle of DNA
• In sexual reproduction, each
“parent” contributes ½ of the
offspring’s genetic info
– ½ from “mom’s egg” & ½ from
“dad’s sperm”
• The physical characteristics that
show are due to “genetics”
Genes vs Alleles
• A gene is a section of a chromosome that
codes for a specific trait
– EX: Eye Color
• An allele is a variation of that instruction
– EX: Brown vs blue eyes
• Every gene has 2 alleles, which we
represent with a single letter (capital or
lowercase)
– BB or Bb or bb
Genotype vs Phenotype
• Genotype the Genetic code
– BB
• Phenotype  the Physical trait
– Brown eyes
Dominant vs Recessive Alleles
• A dominant allele (represented by a
capital letter), if present, shows that
specific trait
– BB or Bb = Brown Eyes
• A recessive allele (represented by a
lowercase letter), must have both alleles
to show a trait
– bb = Blue eyes
• If both letters are the same, BB or bb, we
say it is HOMOZYGOUS (dominant or
recessive)
• If both letters are different, Bb, we say it
is HETEROZYGOUS
Look at this…
• HH = Does not have trait
• Hh = Does not show trait,
but is a carrier
• hh = shows trait
Trait could be anything
inheritable, such as
baldness or albinism
Let’s watch this video…
• https://www.youtube.com/watch?v=CBe
zq1fFUEA
Punnett Squares
• We can predict the outcome of offspring
by using a PUNNETT SQUARE
Let’s Practice…