Transcript genetics_notes_intro

Intro genetics outline
I. Heredity
II. Traits
ex.
III. Gene
alleles:
IV. Gregor Mendel
self vs. cross
pollination
P, F1, F2
V. Vocabulary and ex.
1. dominant
2. recessive
3. phenotype
4. genotype
5. homozygous
6. heterozygous
VI. Laws
VII.Punnett squares
• Genetics—Branch of Biology that
studies heredity
• Heredity—When traits are passed
from one generation to the next
• Traits—characteristics that are inherited and
vary among individuals
• Ex. Hair color, height, pea color, pea shape
• Gene: segment of DNA that controls a
trait (ex. Height, hair color)
• Alleles—Different forms of a gene or trait,
always have 2 alleles for each trait (one copy
from mom and one copy from dad)
– Ex.T is allele for tall plant, t is allele for
short plant
• Gregor Mendel--Austrian monk who used pea
plants to study how traits are passed from one
generation to the next
• “Father of genetics”
Traits Mendel studied
Pod
color
Pod
Plant
shape height
round yellow purple
axial
(side)
green
inflated
tall
green
terminal
(tips)
yellow
constricted
short
Seed Seed Flower Flower
shape color color position
Dominant
trait
Recessive
trait
wrinkled
white
Pollination = Fertilization in plants
• Self pollination: male and female parts of
same plant produce seeds
offspring is identical to parent (purebred)
• Cross pollination: seeds produced from two
different plants
offspring have different traits than
parents(hybrid)
Mendel’s Experiment
• Mendel bred tall pea plants with short plants
– The offspring in the 1st generation were all tall
– The offspring in the second generation were
75% tall and 25% short
– The short trait disappeared in the 1st generation
and reappeared in the 2nd generation
•P1 generation—original
parents
•F1 generation—first filial
(offspring)
P1
Short pea plant
Tall pea plant
F1
All tall pea plants
•F2 generation – second filial
(grandkids)
F2
3 tall: 1 short
•Dominant—trait that covers
over another trait, capital letter
•Ex. T (tall) is a dominant
allele
•Recessive—trait that is
covered over by another trait,
lower case letter
•Ex. t (short) is the recessive
allele
T-tall
t-short
• Common dominant traits in humans--cleft
chin, widow’s peak hairline, hair on fingers
•Phenotype—physical
appearance, how it looks
•Ex. Phenotype is tall
•Genotype—genetic makeup,
letters
•Ex. Genotype can be TT
or Tt
Tall pea plant
•Homozygous—2 same
alleles for a trait (true
breeding)
•Ex. TT, tt
•Heterozygous—2 different
alleles for a trait,
also called a hybrid
•Ex. Tt
TT, Tt-tall tt-short
Practice
•
1.
2.
3.
4.
5.
T = tall , t = short
If individual is TT, what is phenotype?
Is TT homozygous or heterozygous?
If individual is Tt, what is phenotype?
Is Tt homozygous or heterozygous?
If individual is short, what is genotype?
• Law of segregation—Each gene has 2 alleles
for a trait, after meiosis each gamete receives
one of these alleles (not both)
• Law of independent assortment – Genes for
different trait also separate
ex. Blond hair, blue eyed mom and
brown hair, brown eyed dad can have
kids with one of mom’s and one of
dad’s traits (blond hair and brown eyes)
Punnett squares
• Used to find possible genotypes of
offspring (can make predictions but not
say for sure what offspring parents will
have)
• Probability: chances of a possible
outcome
ex. What is the probability of tossing 4
heads in a row? ½ x ½ x ½ x ½ = 1/16
Practice
•
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T = tall, t = short
Cross TT x tt
Cross Tt x tt
Cross Tt x Tt
In each case, what is the probability of
having tall plants?
• Solve the previous problems following
the teacher’s board demonstrations!!
End of Chapter 10 Show