F 1 generation
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Transcript F 1 generation
GENETICS!
GREGORY MENDEL
Born 1822; Died 1884
Monk and a teacher
Work not recognized until
1900
Studied heredity by
studying pea plants
What is heredity?
MENDEL’S PEA PLANTS
Observed seven
characteristics of pea
plants with two
different traits
Controlled how each
plant was pollinated
Self-pollination or
cross-pollination
What’s the difference?
MENDEL’S EXPERIMENTS
Grew true-breeding plants
What does it mean to be true breeding?
Starting strain called parent generation or P
generation
Cross-pollinated P generation to produce offspring
called the first filial generation or F1 generation
F1 generation self-pollinated and produce the second
filial generation or F2 generation
P
generation
x
P
generation
F1
generation
x
All of the
F1 showed
one color
P
generation
x
F1
generation
F2
generation
F2 produced
plants about
¾ one trait
and ¼ the
other trait
RESULTS
Factor was controlling the traits since there were two
traits there were two factors
Alleles: represent the factors - dominant CAPITAL
LETTERS; recessive lower case letters; They are
alternate forms of genes.
Dominant trait: Able to repress the other trait
Recessive trait: repressed by the dominant
Homozygous: same alleles; RR or rr – also called
purebred or true breeding
Heterozygous: one of each allele forming a hybrid Rr
Genotype: allele pairs/actual DNA: RR, Rr, or rr
Phenotype: physical appearance; red, yellow, green, tall,
short, etc. *You only see the recessive phenotype when
there are two of the recessive alleles. Whenever you see
the dominant phenotype, you cannot tell the genotype.*
Lead to the modern study of molecular genetics, the
study of chromosomes and genes.
Y
y
LAWS OF GENETICS
Law of Segregation: a pair
of factors is segregated or
separated during the
formation of gametes (i.e. the
homologous chromosomes are
separated during anaphase I
of meiosis I into different
gametes.)
Law of Independent
Assortment: factors for
different characteristics are
distributed to gametes
independently – factor for
different traits do not follow
each other into the same
gamete
PROBABILITY
Probability that a specific event will occur; expressed as
a decimal, fraction, or percent
Probability =
Number of times an event happened
Number of possible opportunities
The predicted results are more likely to occur the more
trials that are performed
MONOHYBRID CROSSES
Monohybrid cross: between individuals with one
pair of contrasting traits ( mono = one)
Punnett squares are used to help predict the
probability of a trait
HOMOZYGOUS X HOMOZYGOUS
Crossing two plants
homozygous for color
(P)
One dominant one
recessive
PP x pp
Genotype
4 Pp
Phenotype
4 purple
HOMOZYGOUS X HETEROZYGOUS
Crossing a homozygous
dominant with a
heterozygous plant for
color (P)
PP x Pp
Genotype
2 PP
2 Pp
Phenotype
4 purple
HOMOZYGOUS X HETEROZYGOUS
Crossing a heterozygou
plant with a homozygou
recessive for color (P)
Pp x pp
Genotype
2 Pp
2 pp
Phenotype
2 purple
2 white
HETEROZYGOUS X HETEROZYGOUS
Both heterozygous for
color (P)
Pp x Pp
Genotype
1 PP
2 Pp
1 pp
Phenotype
3 purple
1 white
TESTCROSS
Used to determine the genotype of a individual with an
unknown genotype
Must use an organism of an known genotype hence use
a homozygous recessive