View
225
Download
4
Tags:
Embed Size (px)
Citation preview
Gregor Mendel• Mendel was an Austrian monk.
• Mendel formulated two fundamental laws of heredity in the early 1860's.
• He had studied science and mathematics (including statistics) at the University of Vienna.
• Mendel’s knowledge of statistics later proved valuable in his research on Heredity – the transmission of characteristics from Parent to Offspring.
• Mendel's work was unrecognized until 1900.
Genetics Vocabulary
• Monohybrid cross - cross involving a single pair of genes, one trait
• P – “parents”
• F1 – “kids”
• F2 – “grandkids”
• Law of Segregation: Each organism contains two factors for each trait; factors segregate in the formation of gametes. When two gametes combine during fertilization, the offspring have two factors controlling a specific trait.
• Law of Independent Assortment: states that factors for different characteristics are distributed to gametes independently.
Genetics Vocabulary• Gene - the unit of heredity; a section of DNA
sequence encoding a single protein• Alleles - two genes that occupy the same
position on homologous chromosomes and cover the same trait
• Locus - a fixed location on a strand of DNA where a gene or one of its alleles is located
• Trait: observed expression of the gene (Physical manifestation of information)
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
F1 Crosses
In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?
Genetics Vocabulary
• Dominant - the trait that appears in the heterozygous condition.
Dominant allele capital letter Height ex: T = tall
• Recessive - the trait that is masked in the heterozygous condition.
Recessive allele Recessive allele lowercase letter lowercase letter
Height ex: t = shortHeight ex: t = short
Genetics Vocabulary• Homozygous - having identical genes (one
from each parent) for a particular characteristic.
• Heterozygous - having two different genes for a particular characteristic.
Genotype & Phenotype
Genotype Phenotype
• Genetic makeup• Can’t see• Height ex: TT, Tt, or tt (letter code)
• Physical characteristic/appearance
• Can see• Depends on genotype• Height ex: tall or short
Question: Can two organisms have the same phenotype but have different genotypes? Explain.
Traits exist because of 2 alleles
• Every trait has 2 _______ that determines its phenotype.– AA or Aa or aa
• AA = Homozygous Dominant• Aa = Heterozygous • aa = ___________ __________
• It is because of this, that the recessive trait can disappear in the F1 generation.
Genetics Vocabulary
Punnett squares - used to aid in predicting the probability that certain traits will be inherited by
offspring
• Probability - is the likelihood that a specific event will occur or is the likely outcome a given event will occur from random chance
1. Determine the dominant and recessive trait
Will be stated in the problem
ie. Black is dominant to white in bunnies
Monohybrid Crosses
2. Assign letters for the trait
Dominant trait gets the capital letter
Recessive traits gets the lower case letter
B = blackb = white
5. Determine genotype of offspring
Punnett square holds offspring genotypes
B b
b
b
Genotype = letter code
Bb bb
Bb bb
7. Determine phenotype ratio
Phenotype = what they look like
Count offspring in the Punnett square phenotype ratio = 2 black:2 white
*If ratio doesn’t add up to total number of boxes in the punnett square you’ve made a mistake
Practice Problems
A pure-breed white flower crosses with a pure-breed purple flower. Purple is dominant to white.
• Show the punnett square• What is the genotype of the F1
generation• What is the phenotype of the F1
generation
More practice
A homozygous black rat is crossed with a heterozygous black rat.B = black b = brown
• Show the punnett square• What are the genotypes of F1?• What are the genotype ratio of F1?
More practice
If you had a black rat how could you tell it’s genotype was homozygous or heterozygous?