Download 2.0 classical genetics

What is the law of segregation?
Agenda for Thursday March 29th
1. Probability lab
2. Punnett Squares
Dominant and Recessive
• Dominant – the trait we see (expressed with
capital letter, A)
• Recessive – trait that is masked (expressed
with lower case letter, a)
• Which is better, dominant or recessive?
Dominance
• Organism with two of the same allele –
homozygous
– AA, aa
• Organism with two different alleles –
heterozygous
– Aa
– Dominant trait observed (notice the dominant allele)
Homozygous (pure bred)
Same
HH
hh
Heterozygous (hybrid)
Different
Hh
Rr
Genotype
Allele makeup of an individual
Tt
RR
TT
Rr
tt
rr
Phenotype
Observable characteristics of an individual
Predicting traits
• Punnett Squares
Parent’s Genotype
Parent’s Genotype
What does homozygous and
heterozygous mean?
Agenda for Friday March 30th
1. Punnett Square practice
QuizTuesday
Practice
A Tt (tall) plant is crossed with a tt (short plant).
What percentage of the offspring will be tall?
A green pea sead (gg) is crossed with a hybrid
yellow seed (Gg). What will be the genotypic and
phenotypic ratios of the offspring?
A heterozygous plant (Tt) is crossed with another
heterozygous (Tt) plant. What percentage of the
offspring will be tall?
In guinea pigs, rough coats are dominant over
smooth coats. An Rr guinea pig is crossed with
an Rr guinea pig.
What are the chances of each genotype and
phenotype?
Agenda for Monday April 2nd
1. Go over HW
2. Pop Quiz
3. More practice!!!
4. Lab
Quiz Wednesday– punnett squares
In pea plants, round (R) is dominant to
wrinkled (r). A heterozygous female is
crossed with a wrinkled male. What is the
probability of having an offspring that is
round?
In pea plants, round (R) is dominant to
wrinkled (r). A purebred dominant female
is crossed with a wrinkled male. What is
the probability of having an offspring that
is round?
Dihybrid Cross
• a cross between two individuals looking at two
different traits
For example:
Round vs. wrinkled seeds
green vs. yellow seeds
RRYY/rryy
What is a dihybrid cross?
Agenda for Wednesday Dec 21st
1. Polyploidy
2. Review
Test Tomorrow
Polyploidy
• Most cells are Diploid (2n)
• Some are polyploid
– One or more extra sets of
chromosomes
– Triploid – 3n
• Rarely occurs in animals (deadly in
humans)
– Roughly 1 in 3 plants are polyploidy
• Increased vigor and size
Genetic Recombination
• New combination of genes produced by
crossing over and independent assortment
Why is genetic recombination important?
Gene Linkage
• Genes on same chromosomes are said to be
linked
– Travel together during Meiosis
• Not always true – crossing over occurs
• Genes close together cross over more
frequently
– Make chromosome maps based on that info.
Chromosome Map
• Map genes A, B, C, D
• Frequency of crossing over
– AD = 25%
– AB = 30%
– CD = 15%
– BD = 5%
– BC = 20%
What does polyploid mean?
Agenda for Thursday Dec 22nd
1. Test
2. Reading Guide