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What genes are, their purpose and how gene expression and regulation are controlled.
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What is a Gene? A gene is the basic unit of inheritance.
Gregor Mendel, 1865. Experiments in Plant Hybridization. Verhandlungen des naturforschenden Vereines in Brünn, 4:3-47
Probability # of times outcome is expected/ # of opportunities Given as a fraction, percentage, or proportion of 1
Product Rule: The probability that two independent events both occurring is the product of each event occurring separately.
Using a fair die, the chance of rolling a 1 is 1/6, 16.7%, or .167
Using a pair of fair dice, the chance of rolling two 1s is 1/6 X 1/6 = 1/36 or 0.027
Sum Rule: The probability that either of two mutually exclusive events will occur is the sum of the probability of each event.
Using a fair die, the chance of rolling either a 2 or a 3 1/6 + 1/6 = 1/3 or 0.333
and
or
1/36
Using a pair of fair dice, the chance of rolling two 1s is 1/6 X 1/6 = 1/36 or 0.027
Product Rule: The probability that two independent events both occurring is the product of each event occurring separately.
1/36
1/36
Sum Rule: The probability that either of two mutually exclusive events will occur is the sum of the probability of each event.
Using a pair of fair dice, the chance of rolling a 2 and a 3 or A 3 and a 2 are 1/36 + 1/36= 2/36 or 1/18
You are playing backgammon and your opponent has you on the ropes. However you can knock him off the board with a role of a ten. What is the probability of rolling a ten with two die?
The seven phenotypic pairs studied by Mendel
Gamete – specialized haploid cells that function during reproduction
Egg ♀ Sperm ♂
Plants: Egg is located in Ovule Sperms cells are located in Pollen
Cross-pollination and selfing are two types of crosses
Figure 2-12 part 2
Figure 2-12 part 3
Yellow trait is dominant Green is recessive
Figure 2-12 part 4
Figure 2-12 part 5
Figure 2-12 part 6
Figure 2-12 part 7
Figure 2-12 part 8
Figure 2-12 part 9
Figure 2-12 part 10
Figure 2-12 part 11
Figure 2-12 part 12
Figure 2-12 part 13
Figure 2-12 part 14
Figure 2-12 part 15
Punnett Squares
Test Cross
Table 2-1
These data are pretty darn close to the expected 3:1, but are they close enough to support the hypothesis?
χ2 (chi-square) Test Goodness of Fit
χ2 = Σ(0bserved-Expected)2/Expected
Class Observed Expected (O-E) (O-E)2 (O-E)2/E
round 5474 5493
(75%) -19 361
361/5493= 0.065
wrinkled 1850 1831 (25%)
19 361 361/1831 = 0.197
Total 7324 7325 χ2 = 0.262
Degrees of Freedom = # of independent variables i.e., # of groups -1
χ2 Distribution - degrees of freedom
Prob
abili
ty
χ2 = Σ(0bserved-Expected)2/Expected
Class Observed Expected (O-E) (O-E)2 (O-E)2/E
Yellow 105
Green 95
Total 200 χ2 =
Degrees of Freedom = # of independent variables i.e., # of groups -1
Yellow X Green Test the Hypothesis that it is a Test-Cross
χ2 (chi-square) Test
Important considerations: * the P value is the probability of a deviation at least as large as what was found. A p of 0.05 means that 1 in 20 times, you may find a deviation this large or larger– not never. * having passed the test means that the results are consistent, not that the results prove the hypothesis. * Since the chi-square value is related to 1/# of expected, the test becomes more accurate with larger numbers.
1)Recessive trait present in F1 hybrid -heterozygotes. One maternal copy and One Paternal copy.
2) Recessive trait in progeny was same as in grandparent.
3) Traits found in a 3:1 ratio in F2
generation
Mendel’s First Law of Inheritance
Begins to differentiate Genotype (internally coded trait) from Phenotype (outwardly manifested trait).
Figure 3-3 step4
Forked-Line Diagram for Gamete Frequencies
RrYy Dihybrid
R
r
Y
y
Y
y
1/2
1/2
1/2
1/2
1/2
1/2
Gamete Frequency
RY ½ X ½ = ¼
Ry ½ X ½ = ¼
ry ½ X ½ = ¼
rY ½ X ½ = ¼
χ2 (chi-square) Test χ2 = Σ(0bserved-Expected)2/Expected
Phenotype Observed Expected (O-E) (O-E)2 (O-E)2/E
Round, Yellow
315 313 2 4 0.013
Round, Green
108 104 4 16 0.154
Wrinkled, Yellow
101 104 -3 9 0.087
Wrinkled, Green
32 35 -3 9 0.257
Total 55566
556 χ2 = 0.511
Df = 3
Data are consistent with Independent Segregation
Rules of Inheritance
1) The units of inheritance (genes) come in pairs. Each gamete will get only one of the two units of inheritance . The progeny then gets one maternal and one paternal copy.
2) The segregation of one gene pair is most often independent of the segregation of another gene pair – independent assortment.