Evolution Of Genes And Genomes

Question 1

Gene

Answer 1

A sequence of nucleotides in dna or rna that codes for a molecule that has a function;
A unit of hereditary

Question 2

Genome

Answer 2

The entire complement of DNA sequence in a cell of organism

Question 3

Gene duplication

Answer 3

Unequal cross-over during meiosis
Replication slippage during DNA synthesis
Retrotransposition

Question 4

Retrotransposition

Answer 4

mRNA from a gene is reverse-transcribed to DNA

• integrated into the genome = duplicate of parental copy
• often on a different chromosome
• lack introns

Question 5

Copy number variation

Answer 5

As a chromosome with a new gene duplicate spreads, there is a polymorphism in the number of copies of the gene that individuals carry

Question 6

Exon shuffling

Answer 6

Formation of new genes by assembly of exons from two or more preexisting genes

Question 7

Whole genome duplication

Answer 7

Can occur when the genome of a single species is doubled (autopolyploidy)
Can occur when gametes from 2 species are mutants with unreduced diploid genotypes (allopolyploidy)

Question 8

Fates of a new gene

Answer 8

Most likely lost by random drift or selection over generations
Very small fraction spread to fixation
Copy number variation
Likely destroyed by mutation (pseudogenes)
Seldom remain functional and become permanent
Sub/neofunctionalisation
Deletion

Question 9

Gene birth

Answer 9

Genome duplication (polyploidy/hybridisation)
Gene duplication
Horizontal gene transfer
De novo gene

Question 10

Gene family

Answer 10

A set of loci that arose by duplication and that code for proteins that typically continue to have similar biochemical function

Question 11

Paralogs

Answer 11

Two or more genes that originated by duplication

Question 12

Gene conversion

Answer 12

Unidirectional transfer of DNA from one gene to another

-homogenization of sequences among members of a gene family

Question 13

Concerted evolution

Answer 13

Gene conversion that spreads though all paralogs in the gene family

Question 14

Subfunctionalisation

Answer 14

Gene carries out only some of the roles that the ancestral gene performed

Question 15

Purifying selection

Answer 15

Selection against deleterious mutations

Question 16

Gene trafficking

Answer 16

Movements of genes to new sites in the genome

Parental copy is sometimes lost by deletion

Question 17

dN/dS ratio > 1

Answer 17

Positive selection on non-synonymous mutations

Question 18

Codon bias

Answer 18

Different codons corresponding to the same amino acid appear at different frequencies in the genome
Expression is more efficient when codons match

Question 19

Overlapping genes

Answer 19

Allows genes to share their timing and level of expression

Or allows for a streamlined genome

Question 20

Karyotype

Answer 20

Number and structure of chromosomes

Question 21

Karyotype evolution

Answer 21

Fusion
Fission
Chromosome number

Question 22

Meiotic drive

Answer 22

Preferential attachment to spindle fibers of the egg vs polar body