5) Evolution Flashcards

Question

Describe how neofunctionalisation causes genes to be preserved.

Answer 1

After a gene is duplicated, one copy can accumulate mutations that give it a new beneficial function Each copy now performs a different useful role, so natural selection preserves both

Answer 2

After gene duplication, each copy can lose different parts of the gene's original function Together, the two copies still perform the full set of functions of the ancestral gene Because both are required to carry out all original tasks, natural selection preserves both duplicates

Answer 3

When a duplicated gene copy is not under selection, it may simply persist in the genome by genetic drift With no selective pressure, the gene may be passively preserved

Answer 4

Jumping genes DNA sequences that can move or copy themselves to different locations in the genome Can disrupt genes, regulate gene expression, or increase genome size

Answer 5

Class 1: retrotransposons Class 2: DNA transposons

Answer 6

Retrotransposons: "copy and paste" Donor DNA uses machinery to transcribe the retrotransposon The RNA intermediate is then reverse transcribed into a DNA intermediate that is then re-integrated into target DNA

Answer 7

DNA transposons: "cut and paste" Excised via a protein, cut out of DNA and integrated into target DNA via integrase

Answer 8

Only Class 1 (retrotransposons) Because the original stays where it is, so it is duplicated

Answer 9

Almost 45% Almost all of these are Class 1

Answer 10

Telomeres are repetitive DNA sequences at chromosome ends Duplication of the repeats by telomerase or other mechanisms prevents chromosome shortening during DNA replication, which protects coding DNA and maintains genome stability

Answer 11

When genes from different genomes (e.g. host and endosymbiont) interact to produce a functional outcome Each is dependent on the other and the outcome they produce wouldn't be achieved by either gene alone (e.g. mitochondrial and nuclear genes working together for cellular respiration)

Answer 12

A DNA sequence that controls expression of a gene Works by binding transcription factors or other proteins (e.g. promoters, enhancers, silencers)

Answer 13

1) Cis-elements: DNA sequences located near a gene that regulate its expression, e.g. enhancers, promoters, silencers 2) Trans-elements: factors (usually proteins or RNAs) that regulate gene expression by binding to cis elements (e.g. activators or repressors)

Answer 14

Some important genes in development encode cell-to-cell signalling components like ligands and receptors Outcomes of a signalling pathway are often changes in gene expression in the cell receiving the signal

Answer 15

Stepwise gene regulation Earlier genes regulate later genes TFs encode positional information

Answer 16

Bicoid is a maternal-effect transcription factor deposited as mRNA in the anterior of the egg After translation, it forms an anterior-> posterior gradient that activates zygotic gap genes in a concentration dependent manner Providing positional information for AP axis patterning

Answer 17

Expression depends on enhancer Bicoid affinity High affinity in the anterior region Co-operative binding occurs in the posterior region Creates unique domains

Answer 18

Pair-rule genes (e.g Even-skipped) are expressed in seven stripes Segment-polarity genes are expressed in fourteen stripes Each stripe is controlled by independent cis-regulatory elements that respond to local concentrations of TFs

Answer 19

Hox genes determine the identity of repeated body units In Drosophila, eight Hox genes are arranged in two complexes Their order corresponds to the body regions they affect (colinearity)

Answer 20

A conserved set of genes that control formation, identity, number, and organisation of body parts Functions are context-dependent

Answer 21

Mutations in enhancers or other cis-elements can change gene expression in specific tissues r times without it altering the protein sequence E.g. Drosophila wing pigmentation - darker wings due to increased expression of pigment genes

Answer 22

Changes in TFs (such as expression patterns or binding motifs) can create new interactions with cis-elements Original TF function is retained, but additional functions can emerge

Answer 23

Mutating a coding sequence affects all tissues and processes where the protein is used Potentially causes deleterious effects, altering cis-regulatory elements and allowing for time-specific changes Preserves other functions and enables modular evolution, providing greater flexibility and fewer constraints on evolutionary change

Answer 24

Developmental constraints limit which phenotypes are possible Causes include: limited genetic variation, pleiotropy, strong correlation among traits

Answer 25

Hox genes specify segment identity, e.g. Antennapedia (Antp) normally prevents antennae from forming as legs Mutations can alter this: gain-of-function Antp expressed in the head converts antennae into legs, while loss-of-function Hox mutations can result in homeotic transformations, changing the identity of specific segments

Answer 26

Ubx = Ultrabithorax A transcriptional repressor Prevents wing formation in T3, suppresses limb formation in abdominal segments A1-A8 Loss-of-function mutations may lead to extra wings and limbs in abdominal segments Explains why most arthropods have abdominal legs but flies do not

Answer 27

It allows a single genotype to produce multiple phenotypes suited to different environmental conditions Increases flexibility and survival without requiring genetic changes

Answer 28

When one body segment develops the identity of another segment

5) Evolution Flashcards

(52 cards)