Mendelian Genetics Flashcards
(26 cards)
character
a heritable feature that varies among individuals
e.g. hair colour, widow’s peak, tongue rolling, eye colour etc
trait
each specific variant of a character
arise through mutation
e.g. red hair
What were the conclusions of Mendel’s experiments?
H1. Alternate versions of genes (different alleles) account for
variation in inherited characters.
Alternate versions of genes are termed alleles.
H2. For each character, an organism inherits two alleles, one per parent.
e.g. A purple allele from one parent and a white allele from the other.
H3. If the two alleles differ, the dominant allele is fully expressed in the organism’ s appearance. The other (recessive) allele has no noticeable effect on the organism’s appearance.
H4. The two alleles segregate during gamete production.
i.e. An ovum only receives one of two alleles for a character. The same applies for a sperm.
If different alleles are present in a parent, then 50% of gametes
receive the dominant allele and 50% the recessive allele.
This is Mendel’s law of segregation.
What is true-breeding?
Self-pollinating individuals have the same traits
What does P generation refer to?
True-breeding parental generation
What is hybridisation?
Crossing (crossbreeding) of true-breeding varieties
What is the F1 generation?
First generation offspring of hybridisation
What is the F2 generation?
Generation from allowing F1 hybrids to self-pollinate
How did Mendel contribute to quantitative genetics?
Used large sample sizes and kept accurate records of results
What is a Punnett square used for?
To predict expected ratios of dominant and recessive genes
What is a testcross?
Breeding an unknown genotype with a homozygous recessive individual
i.e. PP or Pp x pp and observe the phenotype of the offspring produced
What are monohybrids?
F1 generation hybrids from breeding experiments following a single character
What are dihybrids?
F1 generation hybrids from breeding which crosses two characters
What is Mendel’s law of independent assortment?
Explains the independence of different traits during inheritance
What are Mendel’s two laws?
Segregation and independent assortment
What is incomplete dominance?
F1 hybrids have an appearance intermediate between two parental varieties
e.g. red parent x white parent = pink offspring
Give an example of incomplete dominance.
Red parent x white parent = pink offspring
e.g. in carnations and snapdragons
What does dominance depend on?
Level of phenotype examined: organismal, biochemical, molecular
True or False: Dominant alleles subdue recessive alleles.
True
True or False: Dominant alleles are necessarily more common in a population.
False
e.g. polydactyly (having an extra digit) is dominant but not neccesarily common
What is pleiotropy?
A single gene with multiple effects in an organism
What is epistasis?
One gene alters the expression of a gene at a separate locus
What is a locus?
Where a gene is physically located in a chromosome
What is polygenic inheritance?
Two or more genes have an additive effect on a single character
e.g. human skin colour
