Genes - Lecture 16 - Mendel's laws and beyond Flashcards
What is true breeding?
Where the parents are homozygous for every trait
What is a monohybrid cross?
There is one gene with two alleles that is being bred
3:1 ratio in F2 generation
What is a dihybrid cross?
There are two genes being bred
There is 9:3:3:1 phenotypic ratio in the F2
What is mendel’s principle of dominance?
In a heterozygote formed by crossing homozygous organisms for contrasting characters, only one character is in the first generation
What is mendel’s principle of segregation?
Alleles of a single gene segregate equally into gametes
What is mendel’s principle of independent assortment?
Alleles of different genes segregate independently into gametes
How is it determined whether an allele is dominant or recessive?
There are different types of mutations which give rise to a LOF or GOF
The type of protein present an decide whether it is dominant or recessive?
Which type of protein leads to recessive alleles?
Loss of function (LOF)
Which type of protein gives rise to dominant alleles?
Gain of function (GOF)
What is incomplete dominance?
When the heterozygote phenotype is intermediate between the two homozygote phenotypes
Both alleles of the gene are partially expressed
Means the phenotype can appear in a gradient form
What is co-dominance?
When a heterozygote shows a phenotype of both alleles
EG blood groups, someone can have blood type AB
What is meant by multiple alleles?
One gene can have more than two alleles
It can form a dominance series, where one is dominant over one allele but recessive to another
What is pleiotropy?
Where a gene can influence more than one trait
EG PDC causes a lack of dynein
It is needed for beating movement of cilia and flagella, so can therefore lead to infertility and also respiratory problems
What are lethal alleles?
They are alleles that stop the survival when they are homozygous or heterozygous
What are the two features used to explain phenotypic variability?
Penetrance
Expressivity
