To solve this problem, we need to identify the methodology used when a geneticist sequences the whole genome of an organism and assigns functions to different segments.$\newline$Let's analyze the options:$\newline \bullet$Option 1: Sequence annotation$\newline$ - Sequence annotation involves identifying and assigning functions to various segments of a sequenced genome.$\newline$ - This process includes identifying genes, regulatory elements, and other functional elements within the genome.$\newline$ - Therefore, this matches the description given in the question.$\newline \bullet$Option 2: Gene mapping$\newline$ - Gene mapping refers to determining the specific locations of genes on a chromosome.$\newline$ - It does not involve sequencing the entire genome or assigning functions to segments.$\newline \bullet$Option 3: Expressed sequence tags$\newline$ - Expressed sequence tags (ESTs) are short sub-sequences of cDNA used to identify gene transcripts.$\newline$ - This is not related to whole genome sequencing or function assignment.$\newline \bullet$Option 4: Bioinformatics$\newline$ - Bioinformatics is a broad field that uses computational tools to analyze biological data.$\newline$ - While it can be used in genome sequencing, it is not a specific methodology for assigning functions to genome segments.$\newline$Based on the analysis, the correct methodology described in the question is Sequence annotation.$\newline$Therefore, the correct option is Option 1.