GENETICS
OBJECTIVE
 Take
a class survey on genetic traits.
 Distinguish



between:
dominant and recessive alleles
homozygous and heterozygous allele pairings
genotype and phenotype
Rolled Tongue
Dimples!!
Widow’s
Peak
Cleft Chin
Straight
hairline
CLASS SURVEY OF GENETIC TRAITS

GENE: a unit of DNA that controls a trait of a
particular organism (ex. Freckles)
Homologous Chromosomes
Allele #1
Allele #2
Gene

ALLELE: an alternative form a gene (one
member of a pair) that is located at a specific
position on a specific chromosome.
DOMINANT allele
An allele that can “mask over” a
recessive allele. Only the
dominant trait is expressed.
It is generally represented by a
CAPTIAL letter
RECESSIVE allele
An allele that can only be
expressed if a dominant allele is
absent.
It is generally represented by a
LOWER CASE letter
Ex. “b”
Ex. “B”
HOMOZYGOUS
(purebred)
HETEROZYGOUS
(hybrid)
A term used to describe a pair
of alleles that are IDENTICAL
or the SAME.
A term used to describe a pair
of alleles that are DIFFERENT.
Ex. BB or bb
Ex. Bb
GENOTYPE
PHENOTYPE
The description of the gene pair. The observable trait that results
from the action of an allele pair.
Ex. BB, Bb, bb
Ex. Brown eyes or blue eyes
Genotype(s):
Phenotype:
Genotype:
Phenotype:
REVIEW
1. A ____________________ allele “masks” recessive
alleles.
2. Another word for purebred is ____________________.
3. You have two ___________________ for eye color.
4. Bb is homozygous or heterozygous?
5. What is the difference between genotype and
phenotype?
OBJECTIVES


To simulate the process of fertilization and
determining the genotypes and phenotypes of
potential offspring
To be able to use a punnett square to predict the
genotype and phenotype probabilities of future
offspring.
HOW TO SET UP YOUR PUNNETT SQUARE
1.
2.
3.
4.
5.
6.
Read the word problem. Identify the dominant
and recessive traits.
Make a key to represent the dominant and
recessive alleles.
Determine the alleles of the parents.
Place the alleles of the parents along the top
and left side of the punnett square.
Cross the alleles inside the boxes.
Determine the ratios of the offspring.
CROSS A HOMOZYGOUS PURPLE FLOWER WITH A
WHITE FLOWER. PURPLE IS DOMINANT TO
WHITE.
PHENOTYPIC
RATIO:
GENOTYPIC
RATIO:
CROSS TWO HETEROZYGOUS BROWN HAIRED
PARENTS. BROWN IS DOMINANT TO BLONDE.
PHENOTYPIC
RATIO:
GENOTYPIC
RATIO:
A HETEROZYGOUS TALL PLANT IS CROSSED
WITH A HOMOZYGOUS SHORT PLANT.
PHENOTYPIC
RATIO:
GENOTYPIC
RATIO:
OBJECTIVE

To trace the genotype and phenotypes of a
particular trait through a family pedigree.
FACEBOOK MESSAGE ON MAY 24TH 2012
Dear family and friends,
As many of you already know, a few weeks ago our family were given
the most devastating news parents could ever receive.
Our son Oliver, at only 25 months old, has been diagnosed with an
incredibly rare genetic disorder called metachromatic leukodystrophy. Our
lives have been shattered and we’re simply at a loss for words.
We know that many of you have been asking after Oliver and how
he’s been doing and since we are not comfortable posting any details on
facebook and we simply do not have the strength to call and retell the same
bad news and updates to everyone we have decided to start a blog that we will
help keep everyone informed on what is going on with us.
There is not much there yet, but I will post in the next few days to
bring everyone up to date. Thank you all for your unending love and support,
it means the world to us.
Sincerely, Katie, Chris and Ollie
Here is our blog: http://www.oliversteam.blogspot.com/
HTTP://WWW.OLIVERSTEAM.BLOGSPOT.COM/

Blog #1: May 30th Have A Cookie Or Three

Blog #2: August 22nd Yah, Equipment!

Blog#3: November 7th Kohl’s Woman

Blog #4: January 20th Failing
PEDIGREE ANALYSIS
Male =
Sibling =
Female =
Fraternal Twins =
Marriage =
Identical Twins =
(Non-identical)
Organization Rules:
1. Generations are numbered using Roman numerals, I, II,
III, etc.
2. Children are placed in birth order starting from the left
side.
KEY
= healthy
= MLD
PEDIGREE
KEY
= brown eyes
= blue eyes
PEDIGREE
KEY
Immune to poison ivy (R) =
Susceptible to poison ivy (r) =
I.
II.
III.
KEY
Six-fingered (F) =
Five-fingered (f) =
OBJECTIVE
 Use
a Punnett square to predict the
genotypic and phenotypic probability
of offspring for:
Incomplete dominance
 Co-dominance


INCOMPLETE DOMINANCE:
A type of inheritance when a heterozygous
geneotype expresses a blending phenotype.
R= red
W= white
#1 Cross a snapdragon white flower with a pink flower.
R= red
W= white
#2 Cross a snapdragon pink flower with a pink flower.
R= curly hair
r = straight hair
#3 Cross a wavy haired person with a straight haired person.

Co-Dominance: 2 alleles are equally dominant
and expressed.

There are 3 alleles for blood typing: A, B, O
A and B alleles are co-dominant
 O allele is recessive
• Even though “O” is capitalized, it is still considered a
recessive allele.

PHENOTYPE
GENOTYPE
“A” blood
AA, AO
“B” blood
BB, BO
“AB” blood
AB
“O” blood
OO
EACH BLOOD TYPE HAS A DIFFERENT
PROTEIN
#1 CROSS A PERSON WITH HOMOZYGOUS “A” BLOOD AND
A PERSON WITH HOMOZYGOUS “B” BLOOD.
#2 CROSS AN “O” BLOOD PERSON WITH A “AB”
BLOOD PERSON.
#3 CROSS A HETEROZYGOUS “A” BLOOD PERSON
WITH A HETEROZYGOUS “B” BLOOD PERSON.
DONATING BLOOD
http://www.redcrossblood.org/learn-about-blood/blood-types
OBJECTIVE
 Use
a Punnett square to predict the
genotypic and phenotypic probability
of sex-linked traits.
COMPLEX INHERITANCE

SEX-LINKED: A type of inheritance where certain
alleles are found only on one sex chromosome (X)

Ex. color-blindness, hemophilia, werewolf syndrome
TEST# 1
TEST# 2
RED-GREEN COLOR BLINDNESS
GREEN-YELLOW COLOR BLINDNESS
BASIC SEX DETERMINATION PUNNETT
SQUARE
PHENOTYPE
GENOTYPE
Normal Female
XBXB
Normal Female
XBXb (carrier)
Abnormal Female
XbXb
Normal Male
XBY
Abnormal Male
XbY
#1 CROSS A COLORBLIND MALE WITH A NORMAL
FEMALE.
#2 CROSS A COLORBLIND MALE WITH A NORMAL
FEMALE CARRIER.
#3 CROSS A NORMAL MALE WITH A NORMAL
FEMALE (THAT HAS A COLORBLIND FATHER).
KEY
Normal =
Colorblind =