Download Tt - kendricknovak

What is the probability of rolling a
1 and 5 in two separate rolls?
Agenda for Tuesday March 30th
• Mendel notes
• Punnett Squares
Law of Segregation
• Chromosomes separate
during meiosis and unite
during fertilization
Law of Independent Assortment
• Random distribution of chromosomes occurring
during meiosis
– Genes on separate chromosomes sort independently
The point?
• It’s all random
– Which alleles we get (genes) (traits)
– Crossing over
– Etc.
What is a trait?
Agenda for Thursday March 31st
1. Mendel
2. Punnett Squares
Mendel
• Father of genetics
• Loved nature
• Austrian monk
– taught natural science
– worked on plant breeding experiments
using pea plants
• Developed basic understanding of
genetics and inheritance
Mendel’s Work
• It took him 2 years to select the pea plant
• He collected data for 10 years.
• His sample sizes were large; he tabulated
results from 28,000 pea plants.
• He replicated his experiments.
• Published work but was dismissed
– Found later
Mendel’s Experiment
• P Generation – parent generation
• F1 generation – first filial generation, offspring
of parents
• F2 generation – second filial generation,
offspring of F1 generation
• Ratio of 3:1
Mendel’s Results
P1
F1
F2
F2 ratio
smooth X wrinkled
seeds
all smooth
5474 smooth
1850 wrinkled
2.96:1
yellow X green
seeds
all yellow
6022 yellow
2001 green
3.01:1
axial X terminal
flowers
all axial
651 axial
207 terminal
3.14:1
red X white flowers
all red
705 red
224 white
3.15:1
882 inflated
299 constricted
2.95:1
all green
428 green
152 yellow
2.82:1
all tall
787 tall
277 dwarf
2.84:1
inflated X
constricted pods
green X yellow pods
tall X dwarf plants
all inflated
Collected
6022 yellow
and 2001
green
3:1 ratio
Conclusions
• 2 forms of seed traits in the pea plants
– Alleles – forms of a gene passed on to each generation
• Green and yellow pea seeds
– We use letters to represents alleles/genes/traits
– Individuals are diploid so we use 2 letters
**Genes are on the chromosomes
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
• Mendel’s experiment, green color was masked
– Recessive
• 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
Punnett Squares
Let’s Practice
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?
Practice
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. If an Rr guinea pig is crossed with
an Rr guinea pig. What are the chances of each
genotype and phenotype? Include genotypic and
phenotypic ratios.
Define homozygous, heterozygous,
phenotype, and genotype
Agenda for Friday April 1st
1.Quiz
2. More practice with Punnett Squares
A Tt (tall) plant is crossed with a tt
(short plant). What percentage of
the offspring will be tall?
• Quiz
• Review Punnett Squares
• Making Dragons
Making Dragons
A Rr (round) seed is crossed with a
Rr (round plant). What are the
phenotypic and genotypic ratios?
• Finish making dragons
• Comparing ratios of Punnett squares to actual
ratios lab
What is the process of combining
two gametes called?
• Finish Comparing Punnett Square ratios
• Dihybrid Crosses
Dihybrid Cross
• a cross between of two individuals that differ
in two traits of particular interest
For example: GGbb/ggBb or RRYY/rryy
What is a dihybrid cross?
• Dihybrid Review
• Gene Linkage and Polyploidy
– Mapping Chromosomes
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%
Polyploidy
• Most cells are Diploid (2n)
• Polyploidy – one or more extra sets of
chromosomes
– Triploid – 3n
• In humans polyploidy is lethal
– Other organisms it is not
– Roughly 1 in 3 plants are polyploidy
• Increased vigor and size