Transcript Mendel`s genetics

Mendelelian
Genetics
I CAN: TELL THE ROLE
OF MEIOSIS IN GENETIC
VARIABILITY.
1
Gregor Mendel
(1822-1884)
Studied the
inheritance of
traits in pea
plants
Developed the
laws of genetics
aka “Father of
Genetics”
Particulate Inheritance
Mendel stated that
physical traits are
inherited as
“particles”
Mendel did not know
that the “particles”
were actually GENES
Genetic Terminology
 Trait - any characteristic that
can be passed from parent to
offspring
 Heredity - passing of traits
from parent to offspring
 Genetics - study of heredity
Punnett Square
A diagram used to
show the
probability of a
trait being
present in
offspring.
“Genes”
 Alleles - two forms of a gene
(dominant & recessive)
 Dominant - stronger of two genes.
Expressed in a cross; represented by
a capital letter (R)
 Recessive - gene that shows up less
often in a cross; is dominated or
overpowered by the dominant gene;
represented by a lowercase letter (r)
More Terminology
 Genotype – genetic makeup or
gene combination for a trait
(e.g. RR, Rr, rr)
 Phenotype - the physical
feature resulting from a
genotype (e.g. red, white)
Genotypes
 Homozygous genotype - gene
combination where both
alleles are alike (e.g. RR or
rr); also called pure bred
 Heterozygous genotype gene combination where the
alleles are different (e.g.
Rr); also called hybrid
Mendel’s Laws
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Law of Dominance
•Some alleles are dominant
and some are recessive.
•When combined in a hybrid,
the dominant overpowers the
recessive.Like  Rr
•The dominant form of the
trait ALWAYS shows in the
phenotype if ONE dominant
gene is present.
Law of Dominance
T = tall (dominant)
t = short (recessive)
R = round (dominant)
r = wrinkled (recessive)
TT – tall
Tt – tall
tt - short
RR – round
Rr – round
rr - wrinkled
Y = yellow (dominant)
y = green (recessive)
P = purple (dominant)
p = white (recessive)
YY –
Yy –
yy -
PP –
Pp –
pp -
Law of Segregation
During meiosis, the two alleles
responsible for a trait separate
from each other.
(when the homologous
chromosomes separate)
Alleles for a trait are
"recombined" at fertilization
Study diagram!!!
Law of Segregation
Let’s Practice Using SpongeBob!!!


Assignments For Today!!
Begin Spongebob
Practice Sheet
Watch Video to
Better Understand
How to use Punnett
Squares.

Practice Doing
Punnett Squares –
Spongebob
Worksheet.
Complete Lecture Quiz
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
Paper Pet Genetics
Power Notes
Female Parent
Meiosis
Female Gametes
Male Parent
M
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S
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s
Male
Gametes
GENOTYPE vs. PHENOTYPE
B – brown eyes (dominant)
b – blue eyes (recessive)
What are the possible genotypes for brown
eyes?
What are the possible genotypes for blue eyes?
W – widow’s peak ( ? )
w – no widow’s peak ( ? )
Possible genotypes for having a widow’s peak:
Possible genotypes for not having a widow’s
peak:
HETEROZYGOUS vs. HOMOZYGOUS
F – free earlobe (dominant)
f – attached earlobe (recessive)
FF – homozygous
Ff –
ff H – hitchhiker’s thumb ( ? )
h – no hitchhiker’s thumb ( ? )
HH –
hh –
Hh -
PUNNETT
SQUARES
Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Homozygous Round seeds x Heterozygous
Round seeds
Genotype:
Phenotype:
Genotypic
Ratio:
Phenotypic
Ratio:
Female Parent
Meiosis
Female Gametes
Male Parent
M
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Male
Gametes
Female Parent
Meiosis
Female Gametes
Male Parent
M
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S
I
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Male
Gametes
ALLELE KEY
TRAIT
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DOMINANT (ALLELE)
RECESSIVE (ALLELE)
TRAITS FOR THE MALE…
TRAIT
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GENOTYPE
PHENOTYPE
TRAITS FOR THE FEMALE…
TRAIT
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GENOTYPE
PHENOTYPE
Complete at least 2 Punnett Squares Using
Parents Genotypes…Show the Percents.
Female Parent
Meiosis
Female Gametes
Male Parent
M
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S
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Male
Gametes
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Last Part of Project
Pick a DIPLOID # for your ORGANISMS
and Draw a Karotype like the one on page
168
Be sure the last pair gives THE sex of
each organism.
Lastly, write or type a one page paper
that explains the following:
••
••
••
•
ITS NICHE (TOTAL WAY OF LIFE
TYPE OF REPRODUCTION, ADAPTATIONS)
DIET (CARNIVORE, HERBIVORE OR OMNIVORE)
HABITAT..(NAME THE BIOME ) DESCRIBE THE CLIMATE
YOUR HYPOTHESIS ABOUT HOW IT WENT EXTINCT
ANY OTHER INTERESTING BIOLOGY STUFF YOU WOULD LIKE TO ADD TO SHOW THE
TEACHER YOU ARE LEARNING 
Types of Genetic Crosses
 Punnett Square - cross
involving a single trait
e.g. flower color
 AKA Monohybrid cross
 Dihybrid cross - cross
involving two traits
e.g. flower color & plant
height
▪ Examines the cross of 2 different traits
Y = Yellow (dominant)
Seed color
y = green (recessive)
R = Round (dominant)
Seed shape
r = wrinkled (recessive)
Cross 2 heterozygous yellow, heterozygous
round plants: what are the genotypes?
Law of Independent
Assortment
Alleles for different traits are
distributed to the gametes
independently of one another.
This law can be illustrated using
dihybrid crosses.
Y = Yellow
y = green
R = Round
r = wrinkled
YyRr
YyRr
Summary of Mendel’s laws
LAW
DOMINANCE
SEGREGATION
INDEPENDENT
ASSORTMENT
PARENT
CROSS
OFFSPRING
TT x tt
tall x short
Tt
100% tall
Tt x Tt
tall x tall
75% tall
25% short
RrGg x RrGg
round & green
x
round & green
9/16 round seeds & green
pods
3/16 round seeds & yellow
pods
3/16 wrinkled seeds & green
pods
1/16 wrinkled seeds & yellow
pods
Non-Mendelian Inheritance
Incomplete Dominance
One trait is not dominant over the
other.
The offspring’s trait is a MIXTURE of
the 2 parents.
+
Codominance
One trait is not dominant over the
other.
BOTH alleles are expressed in the
offspring.
=
+
WW
BB
WB
+
Homozygous Red
Homozygous White
=
Roan
Human Blood type
AA or AO
BB or BO
AB
OO
EXIT TICKET…….
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COMPLETE ALL
PARTS OF THE
MONSTERS
GENETICS
WORKSHEET
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BE SURE TO DRAW
AND COLOR MIKE…
YOU WILL NEED
GREEN AND YELLOW
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GENETICS WITH A SMILE
EACH PARENT CREATE YOUR OWN
BABY BASED ON IT’S TRAITS..
INCLUDE THE FOLLOWING ON YOUR
BABY’S PICTURE:
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BABY’S NAME & PARENT’S NAME
BIRTHDAY
CUTE HAIR BOW IF A GIRL!
NICE NECK-TIE IF A BOY!
SEX LINKED TRAITS
▪ Genes located on sex chromosomes are called
sex-linked genes.
▪ Y chromosome genes in mammals are responsible
for male characteristics.
▪ X chromosome genes in mammals affect many
traits.
SEX LINKED TRAITS
* Most sex linked (X-linked) disorders are
recessive and show up only in males.
* Females are carriers of sex linked
disorders
POLYGENETIC TRAIT
▪Trait produced by 2 or more genes
that interact
▪Human skin color
▪Human eye color
Order of dominance:
brown > green > blue.
PEDIGREES
▪ A pedigree is a chart for tracing genes in
a family
▪Trace phenotypes to infer the genotypes
-Male without trait
-Male with trait
-Male carrier
-Female without trait
-Female with trait
-Female carrier
Autosomal genes: widow’s peak
Sex Linked genes: colorblindness
M – normal color vision
m - colorblind
-Male without trait
-Male with trait
-Male carrier
-Female without trait
-Female with trait
-Female carrier