(3) Gene Linkage & Mapping Flashcards
(24 cards)
Define polymorphism
The occurrence in the same population of two or more alleles at one locus, each with appreciable frequency (>1%) E.g., blood type alleles
What does SNP stand for?
Single nucleotide polymorphism
What is an SNP?
A polymorphism at a single base locus.
E.g., sickle cell anemia results from a SNP
What is a haplotype?
A set of DNA variations, or polymorphisms, that tend to be inherited together. A haplotype can refer to a combination of alleles or to a set of single nucleotide polymorphisms (SNPs) found on the same chromosome.
(T/F) Genes assort independently during meiosis.
False.
Chromosomes, not genes, assort independently during meiosis.
What were Thomas Hunt Morgan’s major contributions to genetics?
- Validated chromosomal theory of heredity
- Discovered sex linkage
- Found that each chromosome carries many genes in a specific order
- Validated the concept of genes as physical entities that are parts of the chromosomes
- Validated evolutionary theory by confirming that closely related species have a similar number of chromosomes and a similar arrangement of genes along the chromosomes
What is often the first step in studying genetic disease?
Finding the location of a specific gene.
Name the two factors that show the importance of linkage analysis
- Knowing the location, we can isolate the gene sequence, which allows us to clone the gene for deeper analysis
- We can better predict the consequence of mutations and large chromosomal changes if we know which genes are involved
Genes located on the same chromosomes are called ___ genes
Syntenic
Syntenic genes that are close together are said to be ___
“Linked”
What does genetic linkage mapping plot?
The position of sentence genes along a chromosome
Who discovered linkage?
William Bateson and Reginal Punnett
How was linkage discovered?
Bateson and Punnett crossed pure-breeding purple-flowered, long-pollen plants to white-flowered, round-pollen plants; the purple, long-pollen F1 were interbred to produce F2. The expected 9:3:3:1 ratio was not observed.
Explain the use of the chi square test.
Used to test the degree to which observed results deviate from expected/predicted results. The larger the chi square the greater the deviation. The p-value is the probability that this deviation can be explained by chance. A p-value below 0.05 indicates significant deviation from our predicted results.
When is complete genetic linkage observed?
When no crossing over occurs between linked genes; only parental gametes are formed.
Drosophila males have no crossing over. What is this an example of?
Complete genetic linkage.
What is produced during incomplete genetic linkage?
A mixture of parental and nonparental gametes.
E.g., the genes controlling human eye colour and hair colour are linked and tend to be inherited together (dark hair with dark eyes, blond hair with blue eyes). Occasionally, they are unlinked through crossing over in meiosis allowing new combinations, like dark hair with blue eyes, to result.
What is the equation for recombinant frequency?
r = number of recombinant gametes / total number of meioses
OR
r = # of recombinant animals / total number of animals
What are the important conclusions drawn from all of Thomas Hunt Morgan’s crosses?
- Genetic linkage is a physical relationship between genes located near one another on a chromosome.
- Recombination occurs between linked genes less than 50% of the time, and greater than 50% of the gametes contain parental allele combinations
- Recombination frequency varies among linked genes in proportion to the distance between them
Fuck you. Review Lecture 3 Slide 36
Kill yourself
What is genetic linkage mapping based on?
Recombination frequency between genes
Who realized that the variations in recombination frequency could be used to determine genetic maps for genes and how?
Morgan’s student, Alfred Sturtevant
He used the results of several experiments to create a genetic map for five X-linked genes
What unit of physical distance can recombination frequencies between two genes be converted into?
Map units (m.u.) or centiMorgan (cM)
What is the conversion centiMorgans to % recombination?
1 centiMorgan = 1% recombination
