Download mendelian genetics powerpoint 2015

GENETICS
I. Heredity:
How traits are passed from parents to offspring
II. GREGOR MENDEL (1822- 1884)
- “Father of Genetics”
- Austrian Monk from 18221884
- Job was to take care of the
garden- worked with peas
- 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, easy traits to view, many
offspring
- Pea plants have DNA just like we do
A. Self Fertilization:
Sperm and egg from the same plant produce offspring
Offspring= Purebred
B. Cross Pollination
process by which sperm from one flower's pollen fertilizes
different flower’s eggs
a. Offspring = Hybrid  heterozygous
HYBRID
COCKER
SPANIEL
+
POODLE
COCKAPOO
HYBRID
PUG
+
BEAGLE
PUGGLE
HYBRID
DOG AND WOLF
Liger
male lion
and
a female
tiger
Peas!
GENETIC
TERMINOLOGY
• Dominant
• Recessive
• Homozygous
• Heterozygous
• Genotype
• Phenotype
• Trait
• Allele
Dominant & Recessive Alleles
• Dominant allele- trait is always expressed
- Written as capital letter
- Ex. Tall= T
• Recessive allele- only expressed if no dominant
allele is present (Dominant allele masks this one)
- For a particular trait written as the same
letter but lower case
- Ex. Short= t
• Homozygous – identical alleles for a trait
– TT, tt
• Heterozygous – not identical alleles for a trait
– Tt
• Genotype- the genes you get from parents
– Two letters represent the two chromosomes
– One from each parents
– Ex: TT, Tt, tt
• Phenotype- the physical trait, what you look like
– “Tall”, “short”, “yellow”, or “green”
Trait = A genetic characteristic
Ex: Height
TALL
 alleles  SHORT
Allele- alternative forms of a gene
Flower Color Trait
Introduction to Monohybrid Crosses
• Punnett Square- chart to predict
offspring
• Monohybrid- looks at ONE trait
•
Ex: Looking at just plant color, or just
height, or just seed color
Reginald Punnett
In Starfish being
red is dominant
over being pink.
What would
Patrick’s
phenotype be?
What would his
genotype be?
Because
Patrick is
pink… his
phenotype is
PINK
And since pink
is recessive –
his genotype
would be “rr”
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. Select a “good” letter to use
2. Write down your “givens”
3. Determine parents and record
4. Set up Punnett Square
5. Determine genotypes &
phenotypes of offspring
(use percentages or fractions)
In pea plants,
Tall is dominant to short
Cross a
Heterozygous Tall plant
with a
Homozygous Tall plant
T
T
t
Tt x TT
T
A
Geno =
T T
T AT
50% T T
50% T t
T t
A
Pheno =
T t
100% Tall
Heterozygous
Blue = Bb
Recessive
Yellow = bb
so we cross…
Bb x bb
Time for some
LOONEY
Monohybrid
Crosses on
your own!
MENDELS LAWS
1. Dominance &
Recessiveness
2.Segregation
3. Independent
Assortment
1. Dominance & Recessiveness
one gene (dominant) can mask
the other (recessive)
2. Segregation
• genes are separated during the formation
of sex cells.
• Offspring inherit only one gene from each
parent.
3. Independent Assortment
• genes for different traits inherited
independently from each other
• In dihybrid crosses, gives you several
possibilities
– Ex: In Nemo- short fin can be inherited with a
red body or an orange body- separate
chromosomes
Independent Assortment
T
E
S
T
C
R
O
S
S
Test Cross:
In a test cross, always cross the unknown
genotype
(TT or Tt) with homozygous recessive (tt).
Using the context of what the results were, will
determine which genotype is the unknown.
PEDIGREE
male
female