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Genetics
Vocabulary
 Allele – a pair of chromosomes
 Dominant – a gene that is always
expressed (seen)
 Gene – a part of a chromosome made
up of DNA
 Hybrid – Having two different types of
genes for a particular trait
Vocabulary
 Offspring – new individuals produced
as a result of reproduction
 Purebred – Having two identical genes
for a trait
 Recessive – Genes that are hidden by
dominant genes, there must be two of
them for the trait to be expressed
(seen)
 Traits – characteristics of an organism
Chromosomes:
 Made up of several
___________
(unit of
Genes
Hereditary
_______________
for a particular trait)
 All human cells have
23
______
pairs (46)
except sex cells have
_____
total
23
 A pair
Allele
(______________)
determines the trait
expressed
DNA:
 Structure:
Double
_______________
helix (twisted
ladder)
 Makes up
Genes
__________
Genetics:
Mendel
Pea

A. Studied ______
plants height,
seed color, and seed shape
Genetics:
B. Dominant Genes
 1. __________
or mask another trait
Hides
Capital letter Ex. Tall = T
 2. Written as a _________
 3. Only1______
gene needs to be present for the trait to be
expressed Ex. Tall = TT or Tt
C. Recessive Genes
 1. ____________
by dominant genes
Hidden
 2. Written as the lower case letter of theDominant
_________
trait
Ex. Short = t
 3. ______
Two are needed for the trait to be expressed
Ex. Short = tt
Genetics:
D. Purebred
Homozygous
1. Also known as _______________________
Same
2. Having the __________
genes for a trait
E. Hybrid
1. Also known as _______________________
Heterozygous
Different
2. Having __________________
genes for a trait
F. Principle of segregation
Alleles
1. States ____________
(gene pairs) separate during
meiosis (formation of gametes)
2. Nondisjunction - occurs when part or all of a
separate
chromosome does not _____________
during meiosis
resulting in too many or too few chromosomes in an egg or
sperm cell ex. Trisomy 21 (Downs Syndrome)
Punnett Squares:
Grid used to determine gene pairs of
________________
Offspring
Example: Tt x Tt
 1. Draw the square
 2. Place one parent at the top of the square
(one gene above each box) and the other
parent to the left of the square (one gene next
to each box).
 3. Write in the top genes in each box below
them.
 4. Write in the side genes in each box to the
right of them. Be sure that the capital letter is
written first in each box.
Punnett Squares:
 5. Determine the genotypes and express as
a ratio or percent.
Dominant : Hybrid : Recessive
1:2:1
Purebred
Purebred
25% Purebred Tall, 50% Hybrid Tall, and
25% Short
 6. Determine the phenotypes and express
as a ratio or percent.
Dominant : Recessive
3:1
75% Tall and 25% Short
Genetics:
 Incomplete Dominance
Blending

A. ____________
of two traits

B. Example: Four o’clock flowers
Variation:
 Causes:
 A. Sexual Reproduction - offspring appear
different from parents due to inheriting
_________
from both parents
Genes
 B. Nondisjunction - Part or all of a
chromosome doesn’t separate during
____________
Meiosis
 C. Mutation - a change in DNA causing a
Trait
change in a ______
Sex Determination
 Sex chromosomes are the 23rd pair
 Females have two x chromosomes
 Males have an x and a y chromosome
Sex Linked Traits
 Traits located on the upper portion of
the x chromosome
 Ex. Colorblindness, baldness,
hemophilia
 They are recessive traits, so they
won’t be expressed (seen) if there is
a dominant gene without the trait
present
Females and Sex Linked Traits
 Inherit 2 dominant x’s without the trait
(don’t exhibit the triat)
 Hybrid – inherit 1 dominant x without the
trait and 1 recessive x with the trait (called
a carrier – does not exhibit the trait but can
pass it to their offspring)
 Inherit 2 recessive x’s with the trait
(exhibits the trait)
 Rare for females to have sex-linked traits
because they need to inherit 2 recessive x’s
Males and Sex Linked Traits
 Inherit 1 dominant x without the trait
(don’t exhibit the trait)
 Inherit 1 recessive x with the trait (exhibits
the trait)
 Males can not be carriers because they only
have 1 x gene (y doesn’t have genes for
these traits)
 Higher percentage of males with sex linked
traits because they only need to inherit 1
recessive x to exhibit the trait
Pedigree Chart:
Traits
 Shows inheritance of ___________
through generations
Genetic Engineering:
 Altering an organisms genetic
material to affect its Traits
____________
Selective
 ________________
breeding breeding organisms with specific
traits
 Cloning - creating new organisms
One
from cells of _______
organism
 Uses - food production and
Medical Purpose
_______________
•A gene is inserted into a fertilized egg so that the
organism that develops will have that trait
•Example: Inserting the gene that allows fish to
survive in icy waters into tomato seeds so that the
tomatoes can survive a frost
•Remove the nucleus from a skin cell (full set of
chromosomes)
•Remove the nucleus from an egg cell
•Insert the skin cell nucleus into the empty egg so it has
a full set of chromosomes
•Egg will divide to produce an identical copy of the
organism that the skin cell came from
•Cloning is a type of asexual reproduction
Review - Heat
 Conduction – heat transfer by direct
contact ex. Frying an egg
 Convection – heat transfer within
fluids (liquids and gases) ex. Boiling
water
 Radiation – heat transfer through
empty space ex. Warming hands by a
campfire
Review – Phase Changes
 Melting – solid to a liquid, heat absorbed
 Freezing – liquid to a solid, heat released
 Condensation – gas to a liquid, heat
released
 Evaporation or Vaporization (Boiling) –
liquid to a gas, heat absorbed
 Sublimation – solid to a gas (no liquid
phase), heat absorbed
 Deposition – gas to a solid (no liquid
phase), heat released