Biochem 3-2 Genomic Oragnization

Front 1

highly repetitive sequences

Back 1

-millions of copies per genome < 3% of genome
-structural, not functional
--mostly located in centromeric and telomeric regions
-usually short strands in *tandem arrays*, repeating end to end, over and over

Front 2

intermediate sequences

Back 2

-100s-1000s per genome
>45% of genome
-majority are transposons, particularly retrotransposons
-only fnx is to propagate own existance

Front 3

rare sequences

Back 3

one copy per genome, >50%

Front 4

Divergences in _____ sequences (single bp alterations or differences in array lengths) can be used as markers in DNA fingerprinting.

Back 4

highly repetitive sequences

Front 5

transposons (jumping genes)

Back 5

sequences capable of moving from location in the genome to another

Front 6

retroviruses (RNA viruses)

Back 6

parasitic DNA molecules capable of moving from one cell to another with the use of an RNA intermediate

Front 7

retrotransposons

Back 7

transposons that move through RNA intermediates. DNA sequences are transcribed into RNA which is then reverse transcribed back into DNA to be reinserted into a chromosome.

Front 8

Most retrotransposons have mutated to lose the ability to jump. What sequence retains this ability in humans and can cause problems?

Back 8

Alu sequence

Front 9

transposons, retroviruses and retrotransposons all belong to which sequence class?

Back 9

intermediate

Front 10

functional intermediate class genes

Back 10

highly abundant rare sequence class genes included in the intermediate class; housekeeping genes, e.g. rRNA, 5S-rRNA, t-RNA and histones.

Front 11

The largest class of gene sequences is he _____ class.

Back 11

rare

Front 12

Most fucntional genes belong to the _____ class.

Back 12

rare

Front 13

gene families

Back 13

groups of genes classed together because they have similar, but not necessarily identical sequences

Front 14

gene families belong to the ____ class of sequences.

Back 14

rare

Front 15

Although gene family members have similar sequences, they differ from the repetitive or intermediate classes in that they are seldom _____, and they are never arranged in _____.

Back 15

identical, tandem arrays

Front 16

homologous genes

Back 16

gene family members are believed to be homologous, which means they eveolved from a common ancestral gene

Front 17

homology

Back 17

estimate of how closely related genes are based on sequence similarity. For instance, if the sequence of two genes is 40% identical, they are said to be 40% homologous.

Front 18

conserved domains

Back 18

duplicated ancestral genes that accumulate bp mutations casuse sequences to diverge; conserved domains are sequences which remain intact.

Front 19

Why is the homology of conserved domains important?

Back 19

Homology remains high in these regions because they are very important to the gene’s function, so any mutations in these regions are selected against because they inactivate the gene and decrease the organism’s viability. Therefore, sequence conservation suggests functional importance.

Front 20

consensus sequence

Back 20

similar sequences from different genes sought in sequence analysis of nucleic acids and proteins; most common base or residue at each position is identified to ascertain the consensus sequence for all the genes.

Front 21

clustered gene families

Back 21

Members of gene families grouped closely together on a chromosome. These clusters differ from the tandem repeats of the repetitive class because the sequences are not identical, they are not as contiguous, and the genes are not necessarily oriented in the same direction.

Front 22

pseudogenes

Back 22

regions with sequences similar to another gene family cluster member, but does not express a gene product, e.g. ᴪ globin and β globin. Believed to evolve from functional genes that were inactivated by mutation.