Lecture 18

Question 1

What is the name given to the representation of the differences between species and their evolution from common ancestors

Answer 1

Phylogenetic tree

Question 2

It has been shown that most of the genes across kingdom Animalia have been relatively conserved. How has this been achieved

Answer 2

BLAST analysis of protein structures to determine regions of significant homology

Question 3

It was determined that what makes members of the animal phyla different is not differences in the genetic sequence as such but what difference was seen

Answer 3

Changes in expression of a common set of genes

Question 4

For great apes and man the change in the nucleotide sequence is about 1% every 10million years, T or F

Answer 4

T

Question 5

If the human and great ape nucleotide sequence changes by roughly 1% every 10 million years and the common ancestor of humans and chimpanzees evolved 5 million years ago, how different are their genomes. Represent this as a fraction and as a number of nucleotides

Answer 5

0.5% difference – 1 in 200 nucleotides

Question 6

Firstly, molecular data is used to distinguish specices which is then backed up by morphological data, T or F

Answer 6

F – vice versa

Question 7

When assembling the phylogenetic tree a specific gene is used to determine relation, this gene is FOXP2. Why is FOXP2 used as a way of differentiating between species

Answer 7

FOXP2 is a highly conserved protein which only shows differences at a few positions in the amino acid sequence

Question 8

Which positions in the amino acid sequence does the FOXP2 vary

Answer 8

80, 303 and 325

Question 9

Mice and chimps both have a threonine residue at position 303, what therefore can be inferred about the common ancestor of these species

Answer 9

Their common ancestor must have also had a 303T

Question 10

Humans and chimps both have 80D in the FOXP2 gene meaning that the common ancestor between these species also possess an 80D. Which amino acid is denoted by D

Answer 10

Aspartate

Question 11

When sorting animals into phyla, programmes similar to BLAST consider all possible relations between animals. How are they then sorted

Answer 11

The tree is assembled based on the simplest model with the fewest changes

Question 12

What is meant by the term parsimony

Answer 12

The idea that you always assume the simplest model

Question 13

Convergent evolution goes against the parsimony model. How does convergent evolution account for differences in the amino acid sequence

Answer 13

Changes in the amino acid sequence of two animals occur independently of each other

Question 14

When assembling the phylogenetic tree, molecular phylogeny is compared with morphological phylogeny and fossil records to give us a deeper understanding of evolution, T or F

Answer 14

T

Question 15

Although there are only 4 families of vertebrate FGF receptors, how many distinct receptors are there

Answer 15

22

Question 16

The Ciona or sea squirt is a distant vertebrate ancestor that only contains 4 FGF receptors. What does this tell us about the common ancestor of Ciona and modern vertebrates

Answer 16

The common ancestor also had only 4 FGF receptors

Question 17

What can explain the other 16 FGF receptors present in vertebrates that aren’t in sea squirts

Answer 17

These will likely have arisen due to genome duplication both locally and by ploidy events

Question 18

What is the name given to a duplicated gene present in the genome

Answer 18

Paralogue

Question 19

Chromosome duplications or duplication mutations are seen frequently when comparing genomes, T or F

Answer 19

T

Question 20

When a gene is first duplicated, what is its role

Answer 20

It is redundant

Question 21

Over time duplicated genes evolve allowing a refinement of function or for a new function to development, T or F

Answer 21

T

Question 22

What ways can the extra copy of a gene change

Answer 22

Can change the pattern of gene expression or the structure/function of the protein

Question 23

Big changes to protein structure are caused by what type of mutations

Answer 23

Domain swapping

Question 24

Smaller changes in the protein structure of a duplicated gene are caused by nonsense mutations, T or F

Answer 24

F – missense mutations

Question 25

What is considered to be the common driving force for morphological evolution of animals

Answer 25

Changes in expression of genes

Question 26

What changes in the transcription machinery present within the DNA explain why expression pattern changes have a major role in morphological evolution

Answer 26

Enhancers can change easily

Question 27

What process can account for bringing a new enhancer regions close to the coding sequence of a gene

Answer 27

Non-homologous recombination

Question 28

Enhancers must occur upstream of a target gene, T or F

Answer 28

F – enhancers can occur anywhere in the gene sequence and their exact position is usually unimportant

Question 29

Changes in protein structure have to be precise so as not to introduce a variety of negative effects. Give some examples of these effects

Answer 29

Introduction of a stop codon, change in the reading frame, interference with protein folding or a disruption in RNA splicing

Question 30

Describe the differences seen in the development of appendages in the fruit fly and Crustacea

Answer 30

Crustaceans development limbs throughout their abdominal and thoracic segments whereas in Drosophila, no legs develop in the abdominal regions

Question 31

Explain the interactions between distal-less and ultrabithorax in forming legs in Drosophila

Answer 31

Distal-less (Dlx) specifies leg precursor cells in the fly embryo and is expressed in the abdominal and thoracic segments. However, ultrabithorax (Ubx) is also expressed in the abdomen where is represses Dlx expression. Thus, legs form only in the thorax of the fly

Question 32

How do Dlx and Ubx act differently in Crustacea to fruit flies

Answer 32

In crustaceans Dlx and Ubx are both expressed in the abdomen and thorax. However, Crustacean Ubx has an anti-repression motif that was lost in insects. Thus dlx expression is not repressed in Crustaceans and abdominal legs develop. These help crustaceans to swim

Question 33

It was found that the Ubx protein in flies lacked an anti-repression domain in the ubx protein. What was seen when comparing the two copies of the ubx gene

Answer 33

There was a dramatic change in the Ubx C-terminus in flies. Crustaceans have a motif that block repression. On the other hand, Drosophila contain a polyalanine amino acid sequence which is absent in Crustaceans

Question 34

What would be the results of ectopic expression of Crustacean ubx in the abdominal segments of Drosophila embryos

Answer 34

Limb formation in the abdomen due to loss of inhibition of dlx expression