18 Questions
What process creates different combinations of alleles in gametes?
Recombination
Where is genetic recombination most likely to occur during meiosis?
Prophase I
What provides clues about which chromosome contains a gene and its precise location on the chromosome?
Gene Mapping
According to Sturtevant, what can be used as an index of the distance between two genetic factors?
Frequency of crossing over
Which process could be used to map out genes on a chromosome if the frequency of crossing over was related to distance?
Crossing over
In genetic mapping, what can offer firm evidence that a disease transmitted from parent to child is linked to certain genes?
Gene Mapping
What do characteristic patterns in the chemical bases that make up DNA, seen only in family members with a certain disease or trait, represent?
Markers
What is the relationship referred to as when genes on a chromosome are so close together that they are always inherited as a single unit?
Complete linkage
How can two genes that are completely linked be differentiated as separate genes?
Through genetic mutations
What type of linkage occurs when two genes show a recombination level greater than 0% and less than 50%?
Incomplete linkage
Which term is used for linked genes that do not independently assort?
Statistical linkage
What is the term for unique patterns in DNA used to identify family members with a certain disease or trait?
Markers
What is genetic recombination?
The exchange of genetic material between multiple chromosomes
Who discovered genetic recombination?
Thomas Hunt Morgan
What is the relationship between recombination frequency and gene distance on a chromosome?
The closer two genes are, the greater the chance of inheritance together
How is DNA recombination generally mediated?
By homology
What happens when genes 'cross over' during genetic recombination?
They exchange information
How did Thomas Hunt Morgan relate recombination frequency to gene distance on a chromosome?
He suggested that the frequency of recombination increased with gene distance
Study Notes
Genetic Recombination
- Recombination occurs during prophase of meiosis and creates different combinations of alleles in the gametes.
- The strength of linkage between two genes depends on the distance between the genes on the chromosome.
- Genes located closer together on a chromosome are more likely to be inherited together.
- Genes located farther away from one another on the same chromosome are more likely to be separated during recombination.
Gene Mapping
- Genetic mapping, also called linkage mapping, provides evidence that a disease is linked to one or more genes.
- Mapping offers clues about which chromosome contains the gene and precisely where the gene lies on that chromosome.
- The frequency of crossing over can be used as an index of the distance between any two genes.
Constructing the First Genetic Map
- Alfred Sturtevant proposed that the proportion of crossovers could be used as an index of the distance between any two genes.
- The Ames test was used to construct the first genetic map.
Types of Linkage
- Complete linkage: genes that are so close together on a chromosome that they are always inherited as a single unit.
- Incomplete linkage: genes that show linkage with a recombination level greater than 0% and less than 50%.
- Statistical linkage: linked genes that do not independently assort, detected as deviation from independent assortment that favors the parental gametes.
Key Figures
- Thomas Hunt Morgan: discovered genetic recombination and proposed that the frequency of recombination was related to the distance between genes on a chromosome.
Test your knowledge on genetic recombination, gene mapping, and linkage between genes on chromosomes. Explore how recombination occurs during prophase of meiosis and creates different combinations of alleles in gametes.
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