Genes & Inheritance Flashcards
Who was Gregor Mendel?
The scientist who first came up with the laws of inheritance. He used pea plants in his controlled breeding experiments.
What are the laws of inheritance?
1) Genes are passed from one generation to the next.
2) Genes can have alternative forms (alleles).
3) Each individual must have two alternative forms per a feature.
4) Sex cells have one of the alternative forms per feature.
5) One allele can be dominant over the other.
What were the results of Mendel’s experiments?
1) The offspring of pure bred parents are always of one type, not a blend of two parental features, but one or the other.
2) The offspring of pure bred first generation in the ratio of 3:1 (three-fourths are the same as the first generation, whereas one-fourth have the other parental feature).
What is a genotype?
This is the genetic make-up of an organism. It describes the alleles each cell has for a certain feature. It is represented by two letters, each representing one allele of the gene that controls the feature.
What is a phenotype?
It refers to the expressed trait of an organism. It is the characteristic of an organism which can be seen and results from the genotype.
What is a dominant gene?
It is the one that always expresses itself, whether in a homozygous or heterozygous combination. It is represented by a capital letter.
What is a recessive gene?
It is the one that is suppressed by a dominant gene and can only express itself it combines with another recessive gene. It is represented by a lower case letter.
What is meant by a homozygous gene combination?
In this type of gene combination, both the genes are similar. They can be either homozygous dominant (TT) or homozygous recessive (tt).
What is meant by a heterozygous gene combination?
It is the type of gene combination in which one gene is dominant and the other is recessive. For example, the heterozygous combination of a tall plant will be Tt.
Explain the concept of co-dominance.
When none of the genes are recessive, both are dominant and neither can suppress the effect of the other completely. Hence, the new individual is the blend of two. This results in an extra phenotype.
What are the alleles in blood groups?
A, B and O
Explain the dominance of blood group alleles.
A and B are dominant over O, but not over each other, hence they are co-dominant.
