Ch 6 Book Terms

Question 1

gene family

Answer 1

A set of genes within a genome that code for related or identical proteins or RNAs. The members were derived by duplication of an ancestral gene followed by accumulation of changes in sequence between the copies. Most often the members are related but not identical.

Question 2

pseudogenes

Answer 2

Inactive but stable components of the genome derived by mutation of an ancestral active gene. Usually they are inactive because of mutations that block transcription or translation or both.

Question 3

tandem duplication

Answer 3

Generation of a chromosome segment that is identical to the segment immediately adjacent to it.

Question 4

translocation

Answer 4

(1) The movement of the ribosome one codon along mRNA after the addition of each amino acid to the polypeptide chain.
(2) The reciprocal or nonreciprocal exchange of chromosomal material between nonhomologous chromosomes.

Question 5

gene clusters

Answer 5

A group of adjacent genes that are identical or related.

Question 6

unequal crossing over (nonreciprocal recombination)

Answer 6

The result of an error in pairing and crossing over in which nonequivalent sites are involved in a recombination event. It produces one recombinant with a deletion of material and one with a duplication.

Question 7

satellite DNA

Answer 7

DNA that consists of many tandem repeats (identical or related) of a short, basic repeating unit.

Question 8

minisatellites

Answer 8

DNAs consisting of tandemly repeated copies of a short, repeating sequence, with more repeat copies than a microsatellite but fewer than a satellite. The length of the repeating unit is measured in tens of base pairs. The number of repeats varies between individual genomes.

Question 9

rDNA

Answer 9

Genes encoding ribosomal RNA (rRNA).

Question 10

nucleolus

Answer 10

A discrete region of the nucleus where ribosomes are produced.

Question 11

nucleolar organizers

Answer 11

The region of a chromosome carrying genes coding for rRNA.

Question 12

nontranscribed spacer

Answer 12

The region between transcription units in a tandem gene cluster.

Question 13

Bam islands

Answer 13

A series of short, repeated sequences found in the nontranscribed spacer of Xenopus rDNA genes.

Question 14

concerted evolution (coincidental evolution)

Answer 14

The ability of two or more related genes to evolve together as though constituting a single locus.

Question 15

gene conversion

Answer 15

The alteration of one strand of a heteroduplex DNA to make it complementary with the other strand at any position(s) where there were mispaired bases or the complete replacement of genetic material at one locus by a homologous sequence.

Question 16

crossover fixation

Answer 16

A possible consequence of unequal crossing over that allows a mutation in one member of a tandem cluster to spread through the whole cluster (or to be eliminated).

Question 17

highly repetitive DNA

Answer 17

Very short DNA sequences (typically < 100 bp) that are present many thousands of times in the genome, often organized as
long regions of tandem repeats.

Question 18

microsatellite

Answer 18

DNAs consisting of tandem repetitions of very short (typically less than 10 bp) units repeated a small number of times.

Question 19

variable number tandem repeat (VNTR)

Answer 19

Very short repeated sequences, including microsatellites and mini-satellites.

Question 20

DNA profiling

Answer 20

Technique used to identify individuals by characteristics of their DNA for the purposes of paternity testing or criminal investigations. Although approximately 99.9% of human DNA sequences are the same in every person, there are enough differences in a person’s DNA that it is possible to distinguish one individual from another (unless they are monozygotic twins). Identification is based on the small set of DNA variations that is likely to differ between unrelated individuals.