Intro to Genetics
Genetics
Student Expectation:
B 6.F
Predict possible outcomes of various genetic combinations such as
monohybrid crosses, dihybrid crosses and non-Mendelian inheritance.
Readiness Standard
Gregor Mendel
Austrian monk born 1822Lived in a monastery
and taught high schoolExperimented with pea plants by cross
breeding plants with different characteristics and studying results.
Known as the father of Genetics
Mendel’s Principles
Law of Inheritance – Characteristics or traits are inherited by individual units known as “genes”.
Vocabulary
Gene – the sequence of DNA that codes for a protein and thus determines a trait.
Example – a gene
will determine plant
height in peas.
Mendel’s Principles
Law of Segregation - states that during the formation of reproductive cells (gametes), pairs of hereditary factors (genes) for a specific trait separate so that offspring receive one factor from each parent.
Vocabulary
Allele – one of a number of different forms of a gene.
Example: this flower carries an allele for white and an allele for purple flowers
Mendel’s Principles
Law of Independent
Assortment - states
that chance deter-
mines which factor
for a particular trait
is inherited.
Mendel’s Principles
Law of Dominance – states that when 2 or more forms of a gene exist (alleles), some forms are dominant and others are recessive
Dominant/Recessive
Hitch Hikers Thumb Normal Thumb
Dominant/Recessive
Free Earlobes Attached Earlobes
Dominant/Recessive
Polydactyly is Dominant!!
Dominant/Recessive
Other examples of dominant traits:
Dimples
Tongue Rolling
Freckles
Curly hair (may be more than one gene)
Dominant/Recessive
Shapes for Pea seedsR = round (Dominant)r = wrinkled (recessive)
Genotype Phenotype RR Round homozygous dominant
Rr Round heterozygous dominant
rr wrinkled homozygous recessive
Monohybrid Crosses
Monohybrid Crosses
Monohybrid Crosses
Practice some monohybrid crosses
BB x BBBB x BbBB x bbBb x BbBb x bb
What are the genotypic ratios?What are the phenotypic ratios?
Dihybrid Crosses
Non Mendelian Genetics
Exceptions to Mendel’s Principles:- Not all genes show simple patterns of
dominant and recessive alleles- The majority of genes have more than
two alleles.- Many traits are controlled by more than
one gene.
Non Mendelian Genetics
Incomplete Dominance - When one allele is not dominant over the other but the heterozygous offspring produce an intermediate (3rd) phenotype. Neither fully expressed.
Example:
Red (RR) x white (rr)
= Pink (Rr)
Non Mendelian Genetics
Co-dominance - Both alleles contribute to the phenotype. Both are expressed at the same time.
Example:Brown BB x White WW= brown and white - BW
Non Mendelian Genetics
Multiple Alleles - More than 2 possible alleles exist – not “either/or”. Only 2 expressed at a
time.
Example: Blood Type
iA, iB, iAiB, ii
Blood Type GenotypeCan Receive Blood From
AiAi = AOiAiA = AA
A or O
BiBi = BOiBiB = BB
B or O
AB iAiB A, B,AB, O
O ii = OO O
Multiple Alleles – Blood Types
Non Mendelian Genetics
Polygenic Traits - Traits controlled by several genes often on multiple chromosomes.
Examples:
Skin Color
Eye Color
Polygenic Traits
Skin Color
Non Mendelian Genetics
Sex Linked Traits -
Genes that are carried
by the sex chromosomes.
Read More: http://anthro.palomar.edu/biobasis/bio_4.htm
Journal Work
In your journal you will work the following punnett squares. This will be a graded assignment.
You must re-write or abbreviate the questions and you must show your work and circle or hi-lite your answers.
Journal Work Problem 1
Identify each of the following as: Homozygous dominant, homozygous recessive or heterozygous.
A. bb B. HybridC. TTD. GgE. Purebred
Journal Work - Problem 2
Dominant/Recessive Monohybrid Cross
Draw a Punnett square and provide the genotypic and phenotypic information.I = Not allergic to Iodine i – allergic to iodine
Ii x II Genotypic ratios Phenotypic ratios
Ii x ii Genotypic ratios Phenotypic ratios
Journal Work - Problem 3
Dominant/Recessive Monohybrid Cross
Two elephants are crossed and the resulting offspring have 50% large ears and 50% small ears.
E = large ears e = small ears
What are the genotypes of the parent?
SHOW YOUR PUNNETT SQUARE.
Journal Work - Problem 4
Dominant/Recessive Monohybrid Cross
A black rabbit is crossed with a white rabbit. 100% of the offspring are heterozygous for color.
B = black b = whiteWhat are the genotypes of the parent?
What are the phenotype percents for the offspring?
SHOW YOUR PUNNETT SQUARE.
Journal Work - Problem 5
Dominant/Recessive Monohybrid Cross
Cross a homozygous fuzzy bear with a hairless bear.
F = fuzzy f – hairless
What are the F1 genotypic ratios?
What are the F1 phenotypic ratios?
Journal Work - Problem 6
Dominant/Recessive Monohybrid Cross
Cross a heterozygous purple-flowered plant with a plant that has white flowers.
P = purple p – white
What are the F1 genotypic ratios? What are the F1 phenotypic ratios?
Journal Work – Problem 7
Dominant/Recessive Dihybrid Cross:
Y – yellow peas P – purple flowers T-tall planty – green peas p – white flowers t – short plant
Cross two heterozygous tall, heterozygous yellow pea plants.
What are the parent genotypes?
What are the F1 genotypic ratios? What are the F1 phenotypic ratios?
Journal Work – Problem 8
Dominant/Recessive Dihybrid Cross:
Y – yellow peas P – purple flowers T-tall planty – green peas p – white flower t – short plant
Cross a short, purple flower plant that is homozygous for color with a short, purple flower plant that is heterozygous for color.
Whate are the parent genotypes?
What are the F1 genotypic ratios? What are the F1 phenotypic ratios?
Journal Work – Problem 9
Dominant/Recessive Dihybrid Cross:
Y – yellow peas P – purple flowers T-tall planty – green peas p – white flower t – short plant
Cross a heterozygous purple flowered, green pea plant with a plant that has white flowers and is heterozygous for pea color.
What are the parent genotypes?
What are the F1 genotypic ratios? What are the F1 phenotypic ratios?
Journal Work – Problem 10
Incomplete Dominance - Monohybrid Cross:In snapdragons, red and white are both dominant.
When they cross, they produce a pink flower.
R – red R’ – white
Cross a homozygous red and a homozygous whitesnapdragon.
What are the parent genotypes?
What are the F1 genotypic ratios? What are the F1 phenotypic ratios?
Journal Work – Problem 11
Co - Dominance - Monohybrid Cross:
In a certain type of chicken, black and white feather share dominance. When they cross they produce chickens with both black and white feathers.
B - black B’ - white
Cross a homozygous black and a homozygous white chicken.
Whate are the parent genotypes?
What are the F1 genotypic ratios? What are the F1 phenotypic ratios?
Journal Work – Problem 12
Incomplete and Co - Dominance - Dihybrid Cross:
In Fuzzy Trolls, Blue and Purple hair are both dominant. A hybrid genotype produces blue and purple stripes. Yellow skin and Red skin are both dominant. A hybrid genotype produces orange skin.
B – Blue hair Y – yellow skin B’ – Purple hair Y’ Red skin
A troll with purple hair and red skin reproduces with a troll with blue hair and orange skin.
What are the parent genotypes?
What are the F1 genotypic ratios? What are the F1 phenotypic ratios?
Journal Work – Problem 13
Multiple Alleles Monohybrid Cross:
Blood Type: Cross a heterozygous Type A with a heterozygous Type B.
Whate are the parent genotypes?
What are the F1 genotypic ratios? What are the F1 phenotypic ratios?
Blood Type GenotypeCan Receive Blood From
AiAi = AOiAiA = AA
A or O
BiBi = BOiBiB = BB
B or O
AB iAiB A, B,AB, O
O ii = OO O
Journal Work – Problem 14
Sex Linked - Monohybrid Cross:
A female who is a carrier for baldness marries a man with normal hair patterns
H – Normal hair pattern h – bald
What are the parent genotypes?
What are the F1 genotypic ratios? What are the F1 phenotypic ratios?