Heredity Flashcards
What did most scientists believe about how traits were inherited during Mendel’s time?
Believed traits were blended in the offspring
What did Mendel’s experiments show about how traits are actually inherited
Traits inherited as discrete units
What do we call these units?
Genes
What is a purebred plant?
Genetically Uniform
Why was it important that Mendel began his experiments with purebred plants?
If he observed change, he would know the result of a cross he made.
When mendel crossed purebred purple with purebred white, he observed only purple flowers in the F1 generation, but purple and white in the F2 generation. How did this help him see that traits are inherited as discrete units?
It helped him see that the units for purple and white were both individually present
What are two conclusions Mendel made which are now called the law of segregation?
- Organisms inherit 2 alleles from each parent for each trait
- organisms only put one allele from each trait in the gametes
What segregates during gamete formation?
2 alleles for each trait
Describe the relationship between the gene; locus and allele
Gene– sequence of DNA codes for each trait
Allele–all aternative forms of that gene
Locus–physical location of gene in a chromosome
What is the difference between genotype and phenotype?
Genotype: Alleles organism has for each trait
Phenotype: Physical expression for the trait
If an organism is heterozygous for a trait, which allele will be expressed, the dominant or recessive allele?
Dominant
What symbols are used to represent the alleles for a gene?
letters
For what is a punnett square used?
Predicting all the possible genotypes of offsprings from a cross
What do the letters on the axes of a square represent?
gametes for each parent
what do the letters in the boxes represent?
Possible offspring
What is a monohybrid cross?
Inheritance of one trait
what is a test cross?
Trying to find genotype of unknown, crossing unknown with homozygous recessive genotype
What is a dihybrid cross?
Looking at inheritance pattern or two different traits
What question did Mendel hope to answer by doing a dihybrid cross?
Did tall purple plants always produce tall purple plants when crossed with short white ones?
Mendel observed the same ratio of phenotypes in the F2 generation of his dihybrid crosses, regardless of which two traits he was studying. What was the ratio?
9:3:3:1
What did Mendel conclude from these resutls?
can be inherited independently
This conclusion is now called Mendel’s second law of genetics. Whats the name of this law?
Law of independent assortment
Describe how this law relates to gamete formation in meiosis
Chromosomes separate independently
In our human traits inventory lab, did we observe the 3:1 ratio of dominant to recessive traits?
no
