Chapter 1: The Mendelian View of the World Flashcards
Published molecular structure of nucleic acid that proposed double helical structure
James watson and Francis crick
Studied the transmission of heredity from one generation to another
Gregor mendel
This experiment illustrates the behavior of each pair of differing traits in a hybrid association is independent of all other differences in the two parental plants
Mendels “Experiments in plant hybridization”
Alternate forms of a gene pair that control a characteristic
Alleles
RR, rr, YY, yy
Homozygous
Rr, Yy
Heterozygous
R and Y
Dominant
r and y
Recessive
Bred True
Produces progeny with a characteristic identical to the parental strains
F1 x F1
F2 generation
True breeding parents are crossed to produce
F1 generation
3:1 phenotypic ratio and 1:2:1: genotypic ratio
F2 generation
Incomplete dominance
Neither dominant nor recessive. Mixes well
Red x White = Pink
Snap dragons flowers are an example of …
incomplete dominance
Co dominance
Neither allele is dominant over the other. No intermediate phenotype. Does not mix well
Red x White = Red/white
When one gene modifies another
Epistasis
Traits controlled by two or more genes
polygenic
What reproduction process produces daughter calls (2n –> 2n)
Mitosis
What reproduction process produces gametes (2n –> 1n)
Meiosis
Crossing over occurs in
meiosis I
- Genes located on separate chromosomes
2. Genes are far apart on same chromosome
Two rules of Independent Assortment
Genotype
Actual genes
Diploid
2n = 46 chromosomes
Haploid
n = 23 chromosomes
Segregation
Separation of two alleles
Independent assortment
Independent sorting of two different traits
This event between two traits restores the original phenotype, resulting in a non-recombinant offspring
Double crossover
What can be performed to determine gene order
a single three-factor cross
Which gene is in the middle of the double cross over?
- 675 ABC, abc
- 25 abC,ABc
- 75 AbC, aBc
- 225 Abc, aBC
C
Multiple traits can be used to determine relative positions of genes on a ____________
Genetic map (linkage map)
1 cM = __ % chance of crossing over
1
Recombination frequency of 28% means
C. They are linked on the same chromosome
One gene pair sorts independently of another gene pair
Independent assortment
Law of Segregation
Genes occur in pairs (allelles) and at the time of gamete formation, one of each pair enters the gametes. Half the gametes carry one allele, the other half the other allele
Law of Independent assortment
Genes for different traits assort independently of one another in the formation of gametes
Principle of Dominance
Some alleles are dominant while others are recessive, and an organism with at least one dominant allele have the dominant phenotype
True or False:
Independent assortment of two traits shows a F2 generation that has a 9:3:3:1 phenotypic ratio
TRUE
True or False:
Allele pairs never segregate
FALSE
True or False:
The principle of segregation states that genes for different traits assort independently of one another in the formation of gametes
FALSE
AaBbcc x AabbCC, probability for aaBbCc
1/4 x 1/2 x 1 = 1/8
From an RrYy x RrYy cross, calculate the probability for genotype RRYy
1/4 x 1/2 = 1/8
Sex linkage
Genes linked to chromosomes
True or false:
Regarding McClintock’s and Creighton’s experiment with corn, the dominant phenotype could only appear as a result of crossing over
FALSE
The RECESSIVE phenotype could only appear as a result of crossing over
