Lecture 16

Question 1

what are germ-line cells vs somatic cells

Answer 1

Germ-line cells:
- cells that give rise to germ cells
- special reproductive cells that carry a copy of the genome to progeny
- mutations in germ-line cells are passed on to offspring

Somatic cell:
- all other cells
- mutations in somatic cells do not get passed onto offspring

Question 2

Give an example of a mutation within a gene

Answer 2

point mutations: changes that affect a single nucleotide pair
- may occur from errors of DNA replication or repair
- may destroy genes activity or rarely improve it
- may have no affect (neutral mutation)

Question 3

Give an example of a mutation within regulatory DNA

Answer 3

• point mutations can also occur in regulatory DNA which will affect gene expression
• for example the regulatory DNA responsible for the expression of lactase is mutated in lactose intolerant individuals such that expression is maintained into adulthood. Normally lactase is only pressed in infancy

Question 4

Gene duplications

Answer 4

• gene duplication can promote emergence of new genes
• mutations in one copy of the gene will be tolerable as long as the other copy remains functional
• this is an example of gene duplication and divergence

Question 5

how do gene duplications arise

Answer 5

• gene duplications arise as a result of homologous recombination
• unequal crossing over results in one long chromosome with gene duplication and one short chromosome

Question 6

What are whole-genome duplications

Answer 6

• instead of single genes , sometime entire genome can be duplicated
• occurs when cell division fails to occur following genome duplication
• for example: X. tropical has a diploid genome and X. laevis has a duplicated genome with twice as much DNA

Question 7

what is the function of exons

Answer 7

• they encode for independent proteins with their own function

Question 8

what is exon shuffling

Answer 8

• it is the duplication and movement of exons so that they can be found in new genes that give rise to new proteins

Question 9

what is mobile genetic elements

Answer 9

• it is a DNA sequence that can move from one location in a chromosome to another
• can disrupt gene if inserted somewhere important (coding sequence, regulatory DNA)
• can create new genes by creating fusion between existing gene and the mobile genetic element
• many carry DNA sequences recognized by transcription regulators

Question 10

horizontal gene transfer

Answer 10

• transfer of DNA from in organism to another
• example: conjugation, transduction, transformation

Question 11

vertical gene transfer

Answer 11

• transfer of DNA from parent to progeny

Question 12

homologous genes

Answer 12

• genes that are similar in sequence due to a common ancestry

Question 13

how to create a phylogenetic tree

Answer 13

• comparisons of nucleotide changes between species can be used to create a phylogenetic tree

Question 14

mutations are found more commonly in…

Answer 14

• mutations are found more commonly in areas of DNA that do not encode for a product or regulate a product because mutations affect survivability/ ability to reproduce

Question 15

essenti genes are _______

Answer 15

highly conserved

Question 16

Conserved synteny

Answer 16

• preservation of gene order and location in the genome of different species
• example: a mouse and human b-globin genes occur in the same order and location

Question 17

Purifying selection

Answer 17

• individuals with mutations that impair important functions have been eliminated

Question 18

Vertebrae genomes

Answer 18

• lose and gain DNA
• all vertebrae genomes contain roughly the same number of gene’s however the overall size varies drastically
  For example: fugu genome is one tenth the size of mammalian genome, but the position of introns and exons are still conserved between fugu and humans

Question 19

Why is rRNA used to create the tree of life to show evolutionary relationship between all organisms

Answer 19

• rRNA is used as a component of the ribosome which is essential for translation
• rRNA should be highly conserved which makes it easier to compare against different organisms