Download Mendel Genetics Problems ppt

Ch. 13, 14
 Physical attributes (hair color)
 Sections of DNA that code for a specific trait
 AGCGTTTACT = red hair (phenotype)
 DNA wrapped around histones
 Different forms of a gene
R: red allele
r: gray allele
 Genotype: Rr
 Phenotype: red hair
 Natural Selection
 Favorable traits are passed on to offspring
 Unfavorable traits mean death & no offspring!
 But he couldn’t figure out how…
 Gregor Mendel: Inheritance
 How traits are passed on (parent  offspring)
 Many varieties:
 white flowering plant or purple flowering plant
 Control reproduction:
 cross-pollinate/hybrid or self-pollinate/purebred
 Short lifespan:
 Three generations in only three years
 P-generation, F1-generation, F2-generation
 Collected thousands of pieces of data
Let’s do some science!
 Self pollinated pea plants to
many generations
 Purebred P-generation
 P gametes
 Resulting F1-generation
 Hybrid
 Law of Dominance
 Genotype:
 Heterozygous alleles
 Pp
 F1 gametes
 Resulting F2-generation
 Phenotype:
 3 purple: 1 white
 Genotype:
 1PP:2Pp:1pp
 Discrete units of a trait segregate into separate
gametes during gamete formation
 In rabbits long ears are dominant to floppy ears. If a
purebred long eared rabbit mates with a hybrid rabbit,
what is the probability a bunny will be a hybrid?
 Observing two traits in one cross
 P-generation gametes:
 Purebred:
 round RR yellow YY
 Purebred:
 green rr wrinkled yy
 Resulting F1-generation?
 P-generation gametes:
 Purebred:
 round RR yellow YY
 Purebred:
 green rr wrinkled yy
 Resulting F1-generation
 Hybrid
 Round Rr and Yellow Yy
 Resulting F2-generation?
 F1-generation gametes
 (RrYy X RrYy)
 Resulting F2-generation
 All pea styles
 The inheritance of one gene does not influence
inheritance of another
 In cats Brown hair (B) is
dominant to white hair (b)
AND short tail (S) is
dominant to long tail (s)
 cross a purebred short
tailed, white cat with a
purebred brown, long
tailed cat
 In cats Brown hair (B) is
dominant to white hair (b)
AND short tail (S) is
dominant to long tail (s)
 Parents: SSbb X ssBB
 FOIL:
 In cats Brown hair (B) is
dominant to white hair (b)
AND short tail (S) is
dominant to long tail (s)
 F1: Hybrid for both traits
 SsBb
 F2 generation??????
 In cats Brown hair (B) is
dominant to white hair (b)
AND short tail (S) is
dominant to long tail (s)
 F2 Generation
 9 brown and short tail
 3 white and short tail
 3 brown and long tail
 1 white and long tail
Life is complex
 F1 hybrids have an
intermediate appearance
 Ex: Snapdragons
 red x white 
 F1 hybrids have an
intermediate appearance
 Ex: Snapdragons
 red x white  pink
 Key
 RR - red
 RW - pink
 WW - white
 Both alleles are expressed dominantly
 Neither allele is recessive
 Ex: Roan horses
 red x white 
 Both alleles are expressed dominantly
 Neither allele is recessive
 Ex: Roan horses
 red x white  Red and White
 Key
 RR - red
 RW - roan
 WW - white
 More than two alleles are present for one trait
 Ex: Blood Groups
 A is dominant over O
 B is dominant over O
 A & B are codominant
 More than two alleles are present for one trait
 Ex: Blood Groups
 A is dominant over O
 B is dominant over O
 A & B are codominant
 Key
 AA & AO: type A
 BB & BO: type B
 AB: type AB
 OO: type O
 Traits that are associated with the
X chromosome
 Ex: Red-green colorblindness
 Traits that are associated with the
X chromosome
 Ex: Red-green colorblindness
 Key:
 XCXC: female normal
 XCXc: female carrier
 XcXc: female colorblind
 XCY: male normal
 XcY: male colorblind
 Multiple genes affect one
trait
 Gene 1 codes for brown
or black mice
 Gene 2 codes for
pigment in general
 One gene affects
multiple traits
 Ex: Cats with blue eyes
are deaf
 A continuum of one trait
is affected by multiple
genes
 Ex: human skin color
 Three separate genes
code for 7 shades of skin
color
 Show relationships within a family
 Track traits or disease in a family
 Dominant or Recessive?
 Dominant or Recessive?
 Occurs when an
individual receives an
extra 21st chromosome
 Causes Down’s
Syndrome
 Occurs when an
individual receives
an extra 13th
chromosome
 Causes Patau
Syndrome
 Occurs when males
receive an extra X
chromosome
 Causes men to be
sterile
 Occurs when males
receive an extra Y
chromosome.
 Causes men to
become overly
aggressive
 Occurs when females
only receive one X
chromosome
 Causes Turners
Syndrome