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Study Guide for the Heredity Test
Date of Test: _________
 heredity: the passing of traits from parents to offspring
 offspring- the young (or baby) of two parents
 probability: the mathematical chance that an event will occur
 phenotype: an organism’s inherited physical appearance (blue eyes, tall, curly hair)
 genotype: an organism’s inherited combination of alleles (BB or Tt)
 alleles: two forms of the same gene (represented by letters such as TT, Tt, or tt) These
may be dominant or recessive. Alleles make up your genotype
 dominant trait: a trait observed when at least one dominant allele (capital letter) for a
characteristic is inherited (for example Rr or RR). When present a dominant trait
will cover up a recessive trait and will ALWAYS appear in the first generation
offspring.
 recessive trait: a trait that is apparent only when two recessive alleles (small letters) for
the same characteristic are inherited (for example rr or bb) This trait recedes
into the background in first generation offspring.
 generation: all of the people born at about the same time (example brothers and sisters)
 Genes: set of instructions donated by parents to offspring (genes are found on
chromosomes)
 Sex cell: sperm and egg cells which hold half the number of chromosomes as body cells
 Sex chromosomes: The X and Y Chromosomes that are responsible for determining an
organism’s gender. XX= female XY= male
 Mitosis: is the process in which one cell copies its DNA and divides into two identical
body cells that have the same number of chromosomes as the parent cell.
(produces 2 identical daughter cells)
 Meiosis: is the process in which one cell goes through two divisions to become four
separate sex cells (sperm and egg cells have half the amount of chromosomes)
Back 
Important People:
-
Punnett developed a square that is used to visualize all the possible combinations of alleles
in offspring resulting from a genetic cross.
- Gregor Mendel was the first to discover genetics.
He used plants to study the way traits
are passed from one generation to the next
Know the difference between mitosis and meiosis
Kind of cell
made
Number of
cells made
Mitosis
body cell
2
Meiosis
sex cell (egg
or sperm)
4
A= Red apples
Number of
chromosomes
made
same as
original cell
Half as many
as the original
cell
Purpose of
cell
Growth and
Repair
Reproduction
a= green apples
Statistics:
Genotype Ratio
Phenotype Ratio
1 : 2 : 1
AA
Aa
aa
3
:
Red apples
Phenotype Percentage
1
green apple
75% or 3 red apples
4
25% or 1_ green apples
4