Mendel's Laws of Inheritance Flashcards
What is the mlcr unit of heredity?
gene
means the thing that is actually passed from parent to offspring
What are gene variants called? What is another description for gene variant?
alleles; different forms of a gene
each trait has at least ____ alleles for a given ____
- 2
- gene
some genes have more than 2 what? what is an example?
alleles
- ie. ABO blood type
one trait is always coded by one gene. T or F?
false. sometimes more than one gene can code for one trait
what is a locus?
the location of the alleles for a gene for a trait on a chromosome
What does homozygous dominant mean?
you have 2 of the same alleles that are both dominant for the trait from both parents
ie. AA
What does heterozygous mean?
you have one dominant and one recessive allele for the trait
ie. Aa
What does homozygous recessive mean?
you have 2 of the same alleles that are both recessive for the trait from both parents
ie. aa
What is phenotype?
the physical appearance/ expression from the alleles for the gene that you have
What is genotype?
the actual set of alleles you have
What are the 3 Mendel’s laws of heredity?
- Law of dominance
- Law of segregation
- Law of independent assortment
Explain the law of dominance
a heterozygous individual with a dominant allele and recessive allele for a trait will show the dominant trait bc the dominant allele masks the recessive allele.
a mendelian law
Explain the law of segregation
each gamete only contains ONE gene copy aka ALLELE of a single trait.
* this is randomly selected during gamete formation
* one gamete is randomly chosen for fertilization
a mendelian law
Explain the law of independent assortment
a pair of traits will segregate INDEPENDENTLY from each other during gamete formation; traits DO NOT influence each other
* exception: linked traits
think about a dihybrid cross
What are 2 examples of non-mendelian inheritance?
- incomplete dominance
- co-dominance
Explain incomplete dominance. Give an example.
- no dominant or recessive allele aka both are expressed and there is a mixed/ intermediate phenotype in the heterozygote
- example: flower color (RR= red; WW= white; RW= pink)
Explain co-dominance. Give an example
- both alleles are expressed, but there is NO mixing like incomplete dominance / when 2 dominant alleles are present, both are expressed
- example: ABO blood type (A and B are co-dominant and O is recessive)
-AB blood. the RBC’s have BOTH A and B antigens on the surface
How can you distinguish mendelian from NON-mendelian inheritance?
if there are two HETEROZYGOUS PARENTS,
* if dealing with one trait, then look for the 3:1 phenotypic ratio of dominant to recessive trait in the F2 generation
* OR
* if dealing with two traits, then look for the 9:3:3:1 phenotypic ratio of 2 dominant traits: one dominant and one recessive trait: 2 recessive traits in the F2 generation.
if the ratios ARE MET = MENDELIAN inheritance IS present
how many traits are involved in a monohydrid cross? What is a typical heterozygous cross phenotypic and genotypic ratio?
- 1 trait
- 2 heterozygous parents phenotypic ratio: 3: 1 [dominant: recessive]
- 2 heterozygous parents genotypic ratio: 1: 2: 1 [ homozygous dominant: heterozygous: homozygous recessive]
how many traits are involved in a dihybrid cross? What is the typical phenotypic ratio for 2 heterozygous parents?
- 2 traits
- 2 heterzygous parents phenotypic ratio: 9:3:3:1 [ 2 dominant traits: one dominant and one recessive trait: 2 recessive traits]
What is the general definition of non-mendelian inheritance?
there are factors OTHER than dominant and recessive traits
