Genetics Exam 2

Tetrad stage

occurs during prophase I of meiosis, when homologous chromosomes pair up and form a structure called a tetrad (consisting of four chromatids)

Tetrad

group of 4 chromatids formed when 2 homologous chromosomes align closely

Synapsis

the alignment essential for genetic recombination

linkage

The condition in which genes are present on the same chromosome, causing them to be inherited as a unit, provided that they are not separated by crossing over during meiosis

True

True or False: The chromosome is the unit of transmission during meiosis, NOT the gene

Recombination

crossing over or reshuffling of alleles (always occurs in the tetrad stage)

Frequency of Crossing Over between any 2 loci

= the distance between them (map units)

Recombinant/Crossover gametes

new allele combinations created from crossing over

Non-crossover gametes

2 chromatids not involved in crossing over

Complete linkage produces only…

Parental gametes

Complete linkage Ratio

1:2:1

(Usually observed only when genes are very close together and the number of progeny is relatively small)

Test Cross with F1 produces…

1:1 ration of thin brown and heavy, red flies

Linkage Group

each chromosome represents 1 linkage group