Heredity
Heredity
• Heredity – the
passing of traits from
parent to offspring.
• Dominant traits – one
trait that appears and
other disappears.
• Recessive traits – trait
that is masked by the
dominant gene.
Genes
• Genes – each parent
donate a set of
characteristic instructions
to offspring.
• Alleles – 2 forms of a
gene – 1 from each
parent
• Genotype – inherited
combo of alleles.
• Phenotype – an
organisms appearance
• Probability –
mathematical chance that
an event will occur.
Gregor Mendel
• He lived in Austria in 1822.
• He was a monk that studied
pea plants to learn about
heredity.
• When Gregor breeds pea
plants he noticed that one trait
always appeared and the other
disappeared.
• He concluded that each parent
must donate one set of
chromosomes to the offspring
= genes
• Two forms of a gene = alleles
• Gene – eye color / allele –
brown & blue
Punnett Square
• The punnett square is used to show possibilities
of offspring.
• Genotype = inherited combo of alleles
• Capital letters are dominant
• Lowercase letters are recessive
• Dominant letter always appears first
• The chance that an event will occur = probability.
• Each box in the Punnett Square equals 25%.
Mitosis vs. Meiosis
• Mitosis is the process
where body cells are
reproduced.
• Mitosis is part of the cell
cycle. (4 out of 6 steps)
• Mitosis produces 2 cells
that are identical to the
original body cell.
• Mitosis copies
chromosomes once and
divides once.
• Meiosis is the process
where sex cells are
reproduced.
• Meiosis has 8 steps.
• Meiosis produces 4 cells
that have half of the
genetic information in
each cell.
• Meiosis copies the
chromosomes once and
divides the cells twice.