Download simple genetics powerpoint 2013

GENETICS
I. Heredity: how traits are passed from parents
to offspring
II. GREGOR MENDEL
(1822- 1884)
“Father of Genetics “
• Austrian Monk
• Worked with pea plants
• Noticed that traits were
passed from parent peas to
their offspring
• Before him people believed
in the blending hypothesis
A. Why are pea plants good to study?
• Reproduce quickly
• Self-fertilize
• Easy traits to view, many offspring
• Pea plants have DNA just like people
B. 7 traits Mendel
Studied
III. Fertilization
A. Self Fertilization
Offspring= Purebred
B. Cross Fertilization
a. Offspring = Hybrid
CROSS POLLINATION
HYBRID
COCKER
SPANIEL
+
POODLE
COCKAPOO
HYBRID
PUG
+
BEAGLE
PUGGLE
Liger
male lion
and
a female
tiger
Peas!
GENETIC
TERMINOLOGY
• Dominant
• Recessive
• Homozygous
• Heterozygous
• Genotype
• Phenotype
• Trait
• Allele
IV. Genetic Terminology
A. Dominant allele: trait is always expressed if
present
- Written as capital letter
Ex: Tall = T
B. Recessive allele: only expressed if no
dominant allele is present (Dominant allele
masks this one)
- Written as the same letter but lower case
Ex: Short = t
C. Homozygous – two identical alleles for a
gene
- TT or tt or SS
D. Heterozygous – two different alleles for a
trait
- Tt or Ss
E. Genotype: the genes you get from your
parents
– You get two copies of every trait
– One from mom one from dad
– Ex: TT, Tt, tt
F. Phenotype: the physical
appearance, what you look
like
– Ex: “Tall” “short”
“yellow” or “green”
– Ex: TT, tt what is the
phenotype?
G. Trait: variation of a particular
character
Trait = Height
TALL  alleles  SHORT
H. Each trait is controlled by a gene that is in two
contrasting forms
The different forms of a gene are called alleles.
I. Gene:
section on
DNA that
codes for a
protein
(trait)
Reginald Punnett
Punnett Square:
chart to predict offspring
Monohybrid:
looks at ONE trait
In Starfish being
red is dominant
over being pink.
1)What would
Patrick’s
phenotype be?
2)What would his
genotype be?
1) Because
Patrick is pink…
his phenotype is
PINK
2) And since pink
is recessive – his
genotype would
be “r r”
Red is dominant
over pink
Suppose we had a
HETEROZYGOUS red
starfish.
What would the
genotype be?
Let’s do some…
MONOHYBRID
CROSSES!
Monohybrid means
we are only using
ONE TRAIT
STEP by STEP
1.
2.
3.
4.
5.
Select a letter to use
Write down your “givens”
Determine parents and record
Set up Punnett Square
Determine genotypes & phenotypes
of offspring
(use percentages or fractions)
In pea plants being tall is
dominant over being short
Cross a heterozygous tall plant
with a homozygous tall plant.
Heterozygous tall parent= T t
Homozygous tall parent = T T
Tall= T
short= t
What is the
genotype ratio?
50% TT
50% tt
What is the
phenotype ratio?
100% Tall
T
t
T
TT
Tt
T
TT
T t
Punnett Square
2) Cross two heterozygous tall parents.
What are the
genotypes?
25% TT
50% Tt
25% tt
What is the
phenotype ratio?
75% Tall
25% short
T
t
T
TT
Tt
t
Tt
tt
Heterozygous Blue
= Bb
Recessive Yellow
= bb
so we cross…
Bb x bb
B
b
b
B b
b b
b
B b
b b
Genotype:
50% Bb 50% bb
Phenotype:
50% blue 50% yellow
Time for some
LOONEY
Monohybrid
Crosses on
your own!
Red
is dominant
over Blue
T
E
S
T
C
R
O
S
S
Test Cross: mate an unknown genotype ( TT or Tt)
with homozygous recessive (tt)
MENDELS LAWS
1. Dominance &
Recessiveness
2.Segregation
3. Independent
Assortment
Dominance and Recessiveness
• One gene (dominant) can mask the other
(recessive)
Principle of Segregation
• Genes are
separated or
segregated during
the formation of
sex cells
• Only one gene
from one parent
Independent Assortment
• Genes for traits
separate
independent of
each other
• In Nemo- short fin
can be inherited
with a red body or
an orange body due
to separate
chromosomes
PEDIGREE
male
female
Albino
polydactyly.