lecture 20 - X-linked traits & recombination Flashcards
What are sex-linked traits?
Traits controlled by genes found on the sex chromsomes (X or Y), rather than autosomes.
Why are there different groups inheritance patterns between males?
Due to sex-linked traits, involving genes on sex chromosomes.
What are heterogametic individuals?
Individuals with two different sex chromosomes.
What are homogametic individuals?
Individuals with two identical sex chromosomes/
What is recombination?
The process in which, during meiosis, crossing over leads to homologues that are different from either of the parent homologues, resulting in genetic variation.
Why might offspring have 2 alleles from different parental chromosomes, despite only inheriting one chromosome?
Due to recombination, in which sections of DNA of homologous chromosomes are exchanged, resulting in gametes that have sections/alleles from both parents.
What is the term for the proportion of recombinant gametes produced by meiosis?
Recombination frequency.
How is recombination frequency determined?
Frequency = (number of recombinants)/(total offspring) * 100%
What is a chiasma?
A point of contact between homologous chromosomes that results in the exchange of genetic material. (recombination)
What increases the frequency of recombination of two specific alleles?
Having a greater distance between the two alleles on the chromosome (unlinked genes)
What is the approximate recombination frequency of distant (unlinked) genes?
50%
What is the recombination frequency of close or linked genes?
0-50%
How can the relationship between distance between genes and recombination frequency be described?
Linear
What (arbitrary) unit is used to measure the relative distance between 2 specific genes?
centimorgan (cM)
What is a ‘genetic map’?
A ‘map’ that shows the relative distance between different genes on a chromosome to be compared, allowing recombination frequency to be analysed.
