genomes

Question 1

What is the approximate size of the human genome in base pairs?

Answer 1

The human genome contains approximately 3,000,000,000 base pairs.

Question 2

What is the maximum percentage of the human genome that codes for proteins?

Answer 2

At most, 3% of the human genome codes for proteins.

Question 3

Approximately how many genes does the human genome contain?

Answer 3

The human genome contains approximately 19,600 genes.

Question 4

Roughly what proportion of the human genome consists of regulatory genes?

Answer 4

About 10% of the human genome consists of regulatory genes.

Question 5

Approximately 85% of the human genome is considered ‘junk’ DNA, meaning its deletion would have ____ on fitness.

Answer 5

no effect

Question 6

What is the ‘C’ paradox in genomics?

Answer 6

It is the phenomenon where the size of genomes differs significantly between organisms, not correlating with complexity.

Question 7

What is the term for sequences of DNA that can move to new positions within the genome?

Answer 7

Transposons, also known as mobile genetic elements.

Question 8

Who first developed the idea that genes can move, based on studies of maize in the 1940s?

Answer 8

Barbara McClintock.

Question 9

The simplest transposons produce an enzyme called _____ that allows them to ‘unglue’ and ‘jump’.

Answer 9

transposase

Question 10

What is the mechanism by which retrotransposons insert themselves into a new location in the genome?

Answer 10

They produce RNA, which is then reverse transcribed back into DNA before insertion.

Question 11

How can the movement of transposons act as an agent of evolution and disease?

Answer 11

By producing mutations, which are implicated in some cancers and developmental disorders.

Question 12

What mechanism does a ‘host’ genome use to prevent transposition and its associated mutations?

Answer 12

Methylation is a character favoured to prevent transposition.

Question 13

BovB elements, a type of LINE, make up what percentage of the cow genome?

Answer 13

Around 25% of the cow genome is composed of BovB elements.

Question 14

The BovB elements found in cows are more closely related to elements found in which other animal group?

Answer 14

They are more closely related to elements found in snakes.

Question 15

What is the proposed vector for the horizontal gene transfer of BovB elements into the cow genome?

Answer 15

Ticks are believed to be involved in the acquisition of this DNA.

Question 16

What is the primary function of Antifreeze Glycoproteins (AFGPs) in Northern gaddids like the Arctic cod?

Answer 16

They prevent ice crystals from forming and acting as nucleation sites, keeping the blood from freezing.

Question 17

The evolution of the AFGP gene is a key example of how seemingly ‘irreducibly complex’ systems can arise through what?

Answer 17

Purely naturalistic evolutionary processes like translocation and duplication.

Question 18

What is the repeating amino acid sequence that forms the protein core of the fish Antifreeze Glycoprotein (AFGP)?

Answer 18

Threonine-alanine-alanine (Thr-Ala-Ala).

Question 19

How did the secretory protein component of the AFGP gene become functional?

Answer 19

It became capable of producing the signal protein after a single nucleotide deletion.

Question 20

The entire AFGP system remained nonfunctional until the protogene moved near a nonfunctional DNA region that could serve as a _____.

Answer 20

promoter region

Question 21

Once the AFGP system became functional, how did natural selection refine its antifreeze properties?

Answer 21

By selecting for more duplications of the Thr-Ala-Ala segment, as more repeats confer greater protection.

Question 22

Syncitins

Answer 22

Genes required for the development and function of the mammalian placenta, which originated from endogenous retroviruses.

Question 23

Syncitin genes, crucial for the placenta, originated from genes that once encoded the envelope of a _____.

Answer 23

retrovirus

Question 24

The process where existing genes, such as viral genes for syncitins, are repurposed for a new function is known as what?

Answer 24

Co-option.

Question 25

What is horizontal gene transfer (HGT)?

Answer 25

The movement of genetic material between different organisms, other than by parent-to-offspring inheritance.

Question 26

In multicellular organisms, horizontal gene transfer is generally found to involve a _____ or a _____.

Answer 26

parasite or a symbiote

Question 27

Why is HGT considered a minor source of genetic variation in multicellular organisms?

Answer 27

Because evolutionary trees based on nuclear genes still generally hold true.

Question 28

How did the *Spodoptera* moth acquire an immune barrier via horizontal gene transfer?

Answer 28

It acquired it through a virus that lives in a parasitoid wasp.

Question 29

How did some pea aphids acquire the ability to produce carotenoids, which are usually obtained from food?

Answer 29

Through horizontal gene transfer, which conferred the reddish colour linked to predation avoidance.

Question 30

How has genome sequencing challenged the concept of 'irreducible complexity'?

Answer 30

By reconstructing complex evolutionary paths, like that of the AFGP gene, showing they can form via known natural processes.

Question 31

By comparing genomes, researchers identified 25 new gene groups that appeared at the origin of which major taxon?

Answer 31

Animals.

Question 32

According to genomic analysis of 62 genes, insects are now classified as a type of what?

Answer 32

Crustaceans, as they are nested within the Pancrustacea.

Question 33

Genomic sequencing has led to the argument that there are how many distinct species of giraffe?

Answer 33

Four distinct species, which diverged 1-2 million years ago with no observed gene flow.

Question 34

What is Environmental DNA (eDNA)?

Answer 34

A technique involving the extraction of DNA sequences from environmental samples like soil or water, without capturing the organism itself.

Question 35

Why is it more accurate to speak of 'human genomes' in the plural, rather than a single 'human genome'?

Answer 35

Because genome projects reveal that genetic variation was severely underestimated, with no single representative sequence.

Question 36

Compared to the reference human genome, individuals of recent African descent were found to have how much more DNA?

Answer 36

10% more DNA, highlighting the underestimation of genetic variation.

Question 37

What specific gene shows strong evidence of natural selection in Tibetans for adaptation to high altitude?

Answer 37

The EPAS1 gene, which controls red blood cell production.

Question 38

What percentage of Tibetans carry the specific high-altitude adaptation mutation in the EPAS1 gene, compared to 9% of Han Chinese?

Answer 38

87% of Tibetans carry the mutation.

Question 39

The Bajau people, who dive for long periods, show selection on the PDE10A gene, leading to what physiological adaptation?

Answer 39

Larger spleens, which act as a reservoir of red blood cells.

Question 40

What are the two competing selective pressures that influence the evolution of skin colour in humans?

Answer 40

Protection against UV radiation (favouring darker skin) and the need for vitamin D biosynthesis (favouring lighter skin).

Question 41

Why is the biological concept of 'races' considered invalid based on the genetics of skin colour?

Answer 41

Because skin colour is a superficial trait that does not correlate consistently with any other trait.

Question 42

What evidence suggests human adaptation to past pandemics in East Asian populations?

Answer 42

Strong signs of selection dating back 20,000 years on 420 genes that code for proteins interacting with coronaviruses.

Question 43

What was the initial source of the repeating Thr-Ala-Ala sequence in the fish AFGP core?

Answer 43

A duplication of a noncoding sequence (GCAGCAGCA) that was converted via mutation.