Mendelian genetics Flashcards
(24 cards)
What is genetics?
The study of how traits are inherited
Who was the first to scientifically study inheritance of traits?
Gregor Mendel
What is a trait?
A specific characteristic that varies from one individual to another
Give examples of traits.
- Brown hair
- Blue eyes
- Freckles
What are genes?
The sequence of DNA that codes for a protein and thus determines a trait
What are alleles?
The different possibilities for a given trait
How many alleles does every trait have?
At least two alleles (one from the mother and one from the father)
What does the Law of Dominance state?
When parents with pure, contrasting traits are crossed, only one form of trait appears in the next generation
Define recessive allele.
An allele that only has an effect on the phenotype when present in the homozygous state
Define dominant allele.
An allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state
What is phenotype?
Physical description of an organism
What is genotype?
Combination of alleles for a characteristic
What does homozygous mean?
An organism that carries two identical alleles for a given trait
What is homozygous dominant?
Both alleles in the pair are the dominant trait
What is homozygous recessive?
Both alleles in the pair are the recessive trait
Define heterozygous.
An individual that carries two different alleles for the same trait
What does the Law of Segregation state?
Traits are determined by pairs of alleles that segregate during meiosis
What is the Law of Independent Assortment?
Different pairs of alleles are passed onto the offspring independently of each other
What is a Punnett Square?
A tool to determine the genotypic and phenotypic frequencies expected from a genetic cross
What is a monohybrid cross?
When the parents crossed differ by one trait
What is the expected genotype frequency for a cross of gg x Gg?
50% gg, 50% Gg
What is the expected phenotype frequency for a cross of gg x Gg? is G is allele for yellow and g is allele for green?
50% yellow, 50% green
If long hair is recessive (h) and short hair is dominant (H), what are the genotype probabilities for Hh x Hh?
- 25% HH
- 50% Hh
- 25% hh
What are the steps to create a Punnett Square?
- Determine the gene and alleles
- Determine the genotype of the parents
- Determine the alleles of the gametes
- Create the Punnett Square
- Cross the alleles
- Calculate genotype and phenotype possibilities
