Ch 9 - How Genes and Genomes Evolve

Question 1

Alu sequence

Answer 1

family of mobile genetic elements that comprises about 10% of the human genome; this short, repetitive sequence is no longer mobile on its own, but requires enzymes encoded by other elements to transpose

Question 2

conserved synteny

Answer 2

the preservation of gene order in the genomes of different species

Question 3

exon shuffling

Answer 3

mechanism for the evolution of new genes; in the process, coding sequences from different genes are brought together to generate a protein with a new combination of domains

Question 4

gamete

Answer 4

cell type in a diploid organism that carries only one set of chromosomes and is specialized for sexual reproduction. a sperm or an egg; also called a germ cell

Question 5

gene duplication and divergence

Answer 5

a process by which new genes can form; involves the accidental generation of an additional copy of a stretch of DNA containing one or more genes, followed by an accumulation of mutations that over time can alter the function or expression of either the original or its copy

Question 6

gene family

Answer 6

a set of related genes that has arisen through a process of gene duplication and divergence

Question 7

germ line

Answer 7

the lineage of reproductive cells that contributes to the formation of a new generation of organisms, as distinct from somatic cells, which form the body and leave no descendants in the next generation

Question 8

homologous gene

Answer 8

describes genes, chromosomes or any structures that are similar because of their common evolutionary origin. can also refer to similarities between protein sequences or nucleic acid sequences

Question 9

horizontal gene transfer

Answer 9

process by which DNA is passed from the genome of one organism to that of another, even to an individual from another species. this contrasts with ‘vertical gene transfer’, which refers to the transfer of genetic information from parent to progeny

Question 10

L1 element

Answer 10

type of retrotransposon that constitutes 15% of the human genome; also called LINE-1

Question 11

mobile genetic element

Answer 11

short segment of DNA that can move, sometimes through an RNA intermediate, from one location in a genome to another; an important source of genetic variation in most genomes. also called a transposon

Question 12

open reading frame (ORF)

Answer 12

long sequence of nucleotides that contains no stop codon; used to identify potential protein-coding sequences in DNA

Question 13

phylogenetic tree

Answer 13

diagram or ‘family tree’ showing the evolutionary relationships among groups of organisms or proteins

Question 14

point mutation

Answer 14

change in a single nucleotide pair in a DNA sequence

Question 15

purifying selection

Answer 15

preservation of a specific nucleotide sequence by the elimination of individuals carrying mutations that interfere with its functions

Question 16

retrotransposon

Answer 16

enzyme that can cleave a DNA molecule at a specific short sequence of nucleotides. extensively used in recombinant DNA technology

Question 17

retrovirus

Answer 17

RNA-containing virus that replicates in a cell by first making a double-stranded DNA intermediate that becomes integrated into the cell’s chromosome

Question 18

reverse transcriptase

Answer 18

enzyme that makes a double-stranded DNA copy from a single-stranded RNA template molecule. present in retroviruses and as part of the transposition machinery of retrotransposons

Question 19

single-nucleotide polymorphism (SNP)

Answer 19

form of genetic variation in which one portion of the population differs from another in terms of which nucleotide is found at a particular position in the genome

Question 20

somatic cell

Answer 20

any cell that forms part of the body of a plant or animal that is not a germ cell or gem-line precursor

Question 21

transposon

Answer 21

general name for short segments of DNA that can move from one location to another in the genome. also known as mobile genetic elements

Question 22

virus

Answer 22

particle consisting of nucleic acid (RNA or DNA) enclosed in a protein coat and capable of replicating within a host cell and spreading from cell to cell