Worksheet #2 Name:
1. Briefly describe the two competing theories regarding the origin of Homo sapiens and its distributional
expansion from its origin in Africa.
-The two competing theories regarding the origin of Homo sapiens and the distributional expansion from
Africa are the Multi-regional hypothesis and the Out of Africa 2 model. The multi-regional hypothesis
focuses on a steady evolutionary process that occurred in different regions. It states that early hominid
ancestors migrated out of Africa and that modern human evolution too place in various parts of the
world. The Out of Africa model argues that once anatomically modern humans evolved, they travelled
out of Africa to explore, colonize, and rapidly replace the archaic Homo population.
2. What does the genetic data say about these two hypotheses?
-The genetic data backs up the Out of Africa hypothesis because of the continent’s genetic diversity. This
high level of genetic variety shows that the human population must have evolved there first and then
later spread out.
3. Genetic analyses of the human species originally relied primarily on data from the mitochondrial
genome and the Y-chromosome. What feature of these two portions of the genome make them useful
for population studies such as the recent history of humans?
-Mitochondrial DNA and Y chromosome are mostly used to study the human population history because
of several reasons: Mitochondrial DNA is exclusively transferred from mother to children because
mitochondrial DNA present in sperms usually gets lost at the time of fertilization. So as to study
maternal ancestry researchers use mitochondrial DNA. Even there are different diseases linked to
maternal mitochondria which are inherited from mother to child. Y chromosome is the only
chromosome present in the cell which do not take part in the recombination or exchange their DNA with
another chromosome, unlike others. Therefore, each and every genetic information is transferred from
father to son, this what make Y chromosome so much special than any other chromosomes. Y
chromosome is only present in males, so to study the paternal ancestry, Y chromosome is sequenced and
analyzed by using different software. Different phylogenetic trees and cladograms are studied so as to
carry out the ancestry.
4. One common misconception about methods for identifying genes in genome sequence is by locating all
the start codons (ATG) and stop codons (TGA, TAG, TAA). Briefly explain why this strategy is not
helpful in the identification of genes?
- Each set of nucleotides corresponds to specific amino acid. It can be start or stop codons. If we try
locating both start and stop codons some genomes or amino acid will miss or additionally added. for
example, AUG code for methionine but also act as start codon. Gene's molecular address marks the
gene. It will describe the Gene's exact and accurate position on chromosome, location of that gene
sequence. protein-coding genes are required for identifying the same.
5. How can we identify genes in unmapped genome sequence?
- From the unmapped reads we generated de novo assemblies, after which the generated sequence contigs
were aligned to the NCBI non-redundant nucleotide database using BLAST, identifying the closest
known matching sequence.
