c) Describe the evidence which indicates the presence of ancestral vertebrate gene homologues in lower animal classes
A group of genes that code for the same function in different species is called a gene homologue
Gene homologue = homeobox = HOX provides evidence of ancestral gene
HOX genes are involved in the development of skeletal and neurological structures in vertebrates
o Arranged in a linear pattern on a given chromosome
Same pattern of HOX genes found in lower classes animals such as arthropods, nematodes and molluscs
o Conserved ancestrally and across animal groups
In experiments involving transgenic animals, an amphibian homeobox gene can properly regulate the corresponding gene in mammals; or a mammal homeobox gene can properly regulate the corresponding gene in flies
d) Discuss the evidence available from current research about the evolution of genes and their actions
Evolution of genes and their action:
o The study of amino acids to identify the evolutionary similarities of organisms, replaced by DNA sequencing
o DNA sequencing is easier to do and provides more direct evidence of evolution by analysing the material of inheritance
o Study of DNA sequences insights into the evolution of genes and hence the evolution of life
Analysis of amino acid sequences in haemoglobin and other proteins has allowed evolutionary relationships among vertebrates to be mapped
e) Identify data sources, gather, process and analyse information from secondary sources and use of available evidence to assess the evidence that analysis of genes provides for evolutionary relationships
Many homologous homeobox genes are expressed in physiologically similar structures in vertebrates and invertebrates
o E.g. three specific HOX genes are expressed in head, mouth and limb sites in flies and vertebrates
o Show the actions of genes controlling position and/or timing of organ-system development evolved early and have been conserved
Mammals have 38 HOX genes as small clusters on different chromosomes, share many features in fruit flies
Radiation can easily damage DNA.
o Radiation has existed on earth for millions of years, cells have evolve mechanisms for repairing damaged DNA
o Genes for repairing DNA similar from yeast to humans
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