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Multigene families—__--are common in many organisms. The members of these gene families therefore do what?
groups of genes of identical or similar sequence
encode identical or similar units of biological information
Families of identical genes are generally assumed to do what?
Gene expression is not __and there is a limit to the __
specify RNA molecules or proteins that are needed in large quantities by the cell, continually or at certain times
- rate at which the product of an individual gene can be synthesized
The identities of simple multigene families, ones in which __, support this idea.
Ex: E. coli (explain)
all the genes are the same
have seven copies of its three rRNA genes, which are all needed when the bacterium is adapting to a new environment. But, five copies of each are usually needed for maintenance
Higher organisms also have multiple copies of their __, which are grouped into large clusters where many genes are arranged __
This arrangement does not __, but is more a reflection of the __
- rRNA genes
- head-to-tail in a tandem array
- aid the rate at which the genes can be transcribed
- process that led to the multiple copies
Sometimes, when copies are still not enough, __ occurs, which involves ___
Gene amplification typically occurs in __
- gene amplification
- replication of the rRNA genes into multiple DNA copies which subsequently exist as independent molecules not attached to the chromosomes
- oocytes that are actively developing into mature egg cells
In complex multigene families, the individual gene members are sufficiently different to __
These proteins are therefore able to play slightly different roles. The flexibility provided by these families of genes is sometimes exploited during __
__ are a good example
- code for proteins with distinctive properties
- development of the organism
- Globin proteins
a type of evolutionary relic whose nucleotide sequences have changed to such an extent that they have lost their function altogether