g enetics !. g regory m endel born 1822; died 1884 monk and a teacher work not recognized until 1900...
TRANSCRIPT
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
xP generation
xP generation
F1
generation
All of the F1 showed one color
x
F2 produced plants about ¾ one trait and ¼ the other trait
P generation
F1
generation
F2
generation
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 heterozygous plant with a homozygous 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