genetics- the study of heredity. heredity is the passing of characteristics from parent to offspring
TRANSCRIPT
Genetics- the study of heredity. Heredity is the passing of characteristics from parent to
offspring.
Gregor Mendel-Father of Genetics
Gregor Mendel- 1840’-1860’s did research on heredity.
An Austrian Monk who became the Father of Genetics. Used Pea plants to do test-crosses.
Genetic Crosses
• Parent generation (P1) the first two organisms that are crossed
• F 1 generation - offspring from first generation
• F2 generation-offspring from crossing the F 1 generation. Common in plants and animals
Seed Shape
Flower Position
Seed CoatColor
Seed Color
Pod Color
Plant Height
PodShape
Round
Wrinkled
Round
Yellow
Green
Gray
White
Smooth
Constricted
Green
Yellow
Axial
Terminal
Tall
Short
Yellow Gray Smooth Green Axial Tall
Section 11-1
Figure 11-3 Mendel’s Seven F1Crosses on Pea Plants
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Mendel’s 4 Principles
1. 1. The principle of dominance states that some alleles are dominant and some are recessive.
• 2. The principle of probability can be used to predict offspring outcome.
• 3. The principle of independent assortment states that alleles for different genes usually separate independently of each other.
• 4. The principle of inheritance of biological characteristics -genes are passed from parent to offspring.
Dihybrid Crosses
When two traits that separate
independently of each other are
put into a cross you get 16
Offspring .When both individuals
are heterozygous you get a
9:3:3:1- phenotypic ratio.
(what they look like)
Section 11-3
Figure 11-10 Independent Assortment in Peas
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Beyond Simple Dominant and Recessive Alleles
Some alleles are neither dominant or recessive, and multiple alleles or multiple genes control many traits
Incomplete Dominance- The phenotype of the offspring is intermediate (blend) of the parents. Example :red flowers x white flowers make pink
.
Example Incomplete Dominance
Co-Dominance
Both alleles are expressed equally giving striping spots or checkered appearance. Example: some chickens have equal number of white and black feathers giving a checkered appearance. In cattle red cattle and white cattle make roan cattle (some red patches some white)
Multiple Alleles- In the population of organisms there are more than two
alleles for certain traits. An individual can only have 2 alleles for each trait but more can exist in
the population. Example:
Human blood type A, AB, O, B
Polygenic Traits
Trait produced by the interaction of several genes. This causes a wide variation in outcomes. Example: Human skin color –controlled by 4 different genes
Sex-LinkedThe trait is on the Chromosome that determines
the sex of the offspring. Females=XX Males=XYBecause males only receive one X from their
mother if the trait is on the X it will show up even if it is recessive.
Y chromosome is very small and does not carry many traits .
Examples: Color-blindness, hemophilia