Ch 3 Lecture (The Interrupted Gene)

Question 1

Interrupted Genes

Answer 1

Genes for which the coding sequence is not continuous due to the presence of introns

Question 2

Primary Transcript (pre-mRNA)

Answer 2

The original unmodified RNA product corresponding to a transcription unit

Question 3

RNA Splicing

Answer 3

The process of excising introns from RNA and connecting the exons into a continuous mRNA

Question 4

Mature Transcript

Answer 4

A modified RNA transcript that moves to cytoplasm for translation

Modifications: alterations to 5’ and 3’ ends & removal of introns

Question 5

Mutations in Exons

Answer 5

Can affect polypeptide sequence

Question 6

Mutations in Introns

Answer 6

Can affect RNA processing

Usually deleterious

Most are point mutations at the intron-exon boundary
–most common outcome is a nonsense mutation (X –> stop)

Question 7

Homologous Genes

Answer 7

Genes share a common ancestor

Question 8

Negative Selection

Answer 8

Selection against mutations that alter the function of the polypeptide

Not having changes in exons is favored

Question 9

Positive Selection

Answer 9

An advantageous mutation has a greater fitness relative to those without the mutation

Having changes in exons will be favored

Question 10

Overlapping Gene

Answer 10

A gene in which part of the sequence is found within part of the sequence of another gene

Question 11

Nested Gene

Answer 11

Complete gene inside of the intron of a larger gene

Question 12

Alternative Splicing

Answer 12

Production of different polypeptides by including or excluding individual exons or choosing between alternative exons

Question 13

Gene Family

Answer 13

A set of genes within a genome that encode related or identical RNA or proteins

Derived by duplication of an ancestral gene and accumulation of changes in sequence between copies

*More similar

Question 14

Superfamily

Answer 14

A set of genes all related by presumed descent from a common ancestor

Now show considerable variation

*Very different but still related

Question 15

Orthologous Genes

Answer 15

A special type of homolog

Related genes in different species

Question 16

what stays the same in homologous genes

Answer 16

exon length and organization

Question 17

why do introns mutate more rapidly than exons

Answer 17

exons are under selective pressure to produce a specific polypeptide with a specific function

Question 18

introns may be … than exons if the gene is under positive selection

Answer 18

more highly conserved

Question 19

when introns are being conserved, what parts are the most important

Answer 19

branch points and splice sites

Question 20

example of positive selection

Answer 20

snake venom and prey resistance

Question 21

why are there more interrupted genes in higher-level eukaryotes

Answer 21

Specialized cells, specialized functions, larger, make multiple proteins.

Question 22

the overal length of a eukaryotic gene is determined largely by

Answer 22

the length of the introns