question??? if two blue eyed people have kids, what color eyes will their kids have? if two brown...
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Question???
• If two blue eyed people have kids, what color eyes will their kids have?
• If two brown eyed people have kids, what color eyes will their kids have?
• Have color sticks!
Genetics: Episode IA Monk, His Peas, and Genes
Ag BiologySutherlin AST
Genetics
• What is genetics?– Branch of biology studying heredity
• What is heredity?– Passing of traits from parent to offspring
• What are traits?– Physical characteristics
Genetics
• Gregor Mendel– A monk, 1800’s Austria– First to study and determine
factors of heredity– Used carefully controlled
experiments: only changed one factor at a time
Genetics
• Why peas?– Produce sexually– Male and female
parts on same flower• Male parts are
called?• Female parts are
called?
Genetics
• Pollination – male sex cells (pollen) lands on female parts (pistil)
• Fertilization – DNA from pollen combines with DNA from ovum (egg)– Becomes seed
Genetics
• Self-pollination: male and female sex cells come from same plant
• Cross-pollination: sex cells come from two different plants– Create hybrid
Genetics
• What did Mendel do?– Studied TALL traits and SHORT traits in plants
(parents = P1)– Cross-pollinated these plants to get hybrids
– ALL of the offspring (F1) were TALL
Genetics
• What did Mendel do next?– Took the offspring (F1), then crossed them
together
– This time, not all offspring the same.
Genetics
• What did Mendel do next?– ¾ of plants were tall– ¼ were short plants– This is called a 3:1 ratio
Genetics
So what does this mean?• Unit Factors– Mendel concluded two factors control each trait– We know these are genes• One factor from the mother• One from the father
Genetics
• Unit Factors– For each gene, there are
alleles• Different forms of each
gene• Example: there is a gene
for height (T)
It could be the Tall allele – T It could be the Short allele - t
Genetics
• Unit Factors– Since we have two copies of each gene, three
combinations• Two Tall (TT) alleles• Two Short (tt) alleles• One Tall allele and one
short allele (Tt)
But how is this possible?
Genetics
What else does this mean?• Rule of Dominance– Only one allele is observable– Dominant alleles: observable trait– Recessive alleles: unobservable trait
– So which is dominant for height in pea plants?
Genetics
• So what does each look like?
– TT:
– tt:
– Tt:
Genetics
• What about cows?– If you cross purebred black angus cattle with red
angus cattle, you get black cattle
– What does this mean?
Question:
1. You are growing peas. Use the chart of dominant and recessive genes.
You are crossing axial (AA) and terminal (aa) bud plants. What would the F1 generation be?
Would terminal or axial be more beneficial for the plant?
Mendel’s 7 Traits of Pea Plants
Genetics
• Two organisms can look the same, but carrying different genes
• Phenotype: how an organism looks (think physical)– Tall? Short?
• Genotype: the genes an organism has– Tall: could be Tt– Tall: could be TT
Genetics
• Homozygous – both alleles are the same– TT, tt
• Heterozygous – alleles are different– Tt
All of this, by a monk, in the 1800s!
Genetics
• Dihybrid cross– Looking at just one trait (height) is monohybrid
(one)– But what if we track more than one trait?
Genetics
• Mendel’s Dihybrid Cross– Round peas (R=round, r=wrinkled)– Seed color (Y=yellow, y=green)
Parents (P1)Round Yellow X Wrinkled Green
Genetics
• Mendel’s Dihybrid Cross Parents (P1)
Round Yellow X Wrinkled GreenRRYY rryy
Result? Offspring (F1) ALL Round YellowsRrYy
Genetics
• Mendel’s Dihybrid CrossF1 Cross
X
So now what do you get?
Genetics
• Mendel’s Dihybrid Cross– The point?– Law of Independent Assortment: genes for
different traits are inherited independently of one another (green seeds do not have to be wrinkled!)
Genetics
• Punnett Squares– Tool for projecting Phenotypes and Genotypes of
offspring– Developed by Reginald Punnett (England)
Genetics
• Monohybrid Punnett Square
Genetics
• Dihybrid Punnett Square
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