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Flashcards in Module 6 Deck (38)
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How can the sequence of bases in DNA change (a mutation)?

Substitution, deletion or insertion of one or more nucleotides within a gene


How can chromosome mutations occur?

Deletion, duplication, translocation or inversion


Hoe can genes be regulated by the level of which they operate?

Transcriptional-genes can be turned off or on
Post-transcriptional=mRNA can be modified which regulates translation and the types of proteins produces
Translational=translation can be stopped or started
Post-translational=proteins can be modified after synthesis which changes their function


Describe chromatin remodelling

Type of transcriptional control
-Hetrochromatin is tightly wound DNA, euchromatin is loosely wound
-Transcription can't occur when tightly would because DNA polymerase can not access the genes
Histone modification


Describe histone modifiction

Type of transcriptional control
-Acetylation reduced positive charge on histones, DNA coils less tightly so transcription can occur
-Methylation makes histones more hydrophobic so they are kind tightly to each other, preventing transcription


Describe the lac operon

Type of transcriptional control
-When lactose is present, it binds to the repressor causing it to change shape so that it can no longer bind to the promotor.
-Transcription can then occur


What is the role of cAMP in the lac operon

cAMP binds to the repressor protein and speeds up trnscription


Describe RNA processing

Type of post-transcriptional control
-A cap is added to the 5' end and a tail is added to the 3' end
-This stabilises the mRNA and delays degradation in the cytoplasm
-The cap also aids binding of mRNA to ribosomes
-Splicing occurs, the irons are removed and the externs join together


Describe RNA editing

Type of post-transcriptional control
-The nucleotide sequence of mRNA can be changed through addition, deletion of substitution to synthesis different proteins


Describe translational control

-Degredation of mRNA
-Binding of inhibitory proteins to mRNA prevents binding to ribosomes
-Proteins kinases catalase the addition of phosphate groups, changing the tertiary structure and function of a protein


Describe post-translational control

-Addition of non-protein groups
-Modifying amino acids and the formation of bonds
-Folding or shortening of proteins


What is the homebox?

A section of DNA
Highly conserved (similar) in plants, animals and fungi
Homeobox genes are regulatory genes as they can be switched on or off


What are hot genes responsible for?

Correct positioning of body parts


What is apoptosis?

Programmed cell death, essential for shaping organisms.


What is chlorosis?

When leaves look pale or yellow due to a lack of chlorophyll being produced
Its as a result of environmental factors (lack of light, minerals, virus infections)


Dihybrid cross F2 generation ratio is...



What are recombinant offspring?

Offspring have different combinations of alleles than either parent


What is epistasis?

The interaction of genes at different loci
An epistatic gene may influence the activity of other genes


What is stabilising selection?

The average is selected for and the extremes are selected against


What is directional selection?

Occurs when theres a change in the environment and the most common phenotype is no longer advantageous.
Allele frequency shifts towards extreme phenotypes and evolution occurs


What is disruptive selection?

The extremes are selected for and the norm is selected against


What is allopatric speciation?

More common speciation.
Some members of a population are separated by a physical barrier and are geographically isolated


What is sympatric speciation?

Occurs within populations that share the sma habitat.
More common in plants than animals
When 2 different species interbreed and form a hybrid which can not interbreed. This reproductively isolated the hybrid organisms


How is a DNA profile produced?

DNA is extracted
-Polymerase chain reaction gives enough DNA to develop a profile
Sample is digested
-Restriction endonuclease cut the DNA at specific nucleotide sequences (restriction sites)
DNA fragments are separated
-Electrophoresis moves the charged particles through a medium gel by an electric current.
-DNA is separated and transferred onto a membrane by southern blotting
-Radioactive or fluorescent DNA probes bind to the complementary strands and identify the regions
-Radiocative= Xray
-Fluroescent=UV light to give a pattern of bars


How does DNA sequencing work?

-DNA is mixed with a primer, DNA polymerase, an excess of normal nucleotides and terminator bases
-Mixture is placed in thermal cycler
-At 90'C the double strand seperates
-At 50'C the primers anneal to the DNA
-At 60'C complementary base pairs attatch by DNA polymerase
-Each time a terminator base is incorporated instead of a normal nucleotide, DNA synthesis stops and no more bases are added
-The fluroescent markers on the terminator bases identify the final base of each fragment in minute capillary tubes
-Lasers detect the different colour and therefore the sequence


What colour of the fluorescent tags correspond to the bases?



What is an ecosystem?

An ecosystem is made up of all the living organisms that interact with each other in a defined area, as well as the physical factors present.


How has human activity manipulated biomass through ecosystems?

Agriculture=> competition from other species is removed, reduced threat of predators, simple food chains.


Role of nitrogen-fixing bacteria

Turns atmospheric nitrogen into ammonia


How is there an symbiotic mutualistic relationship between nitrogen fixing bacteria and leguminous plants?

The plants gain amino acids
The bacteria gain carbohydrates produced by the plants during photosynthesis


How does nitrification occur?

Nitrifying bacteria oxidise ammonium compounds into nitrites
Nitrobacter oxidise nitrites into nitrates


Role of denitrifying bacteria

Convert nitrates in the soil back into nitrogen gas
(only under anaerobic condition-waterlogged soil)


What is the process of ammonification?

Where decomposes convert nitrogen-containing molecules in dead organisms into ammonium compounds


What is succession?

Where ecosystems change over time


What are the stages in succession

Pioneer species=>Intermediated community=>climax community


What is the process called when secession is artificially stopped

(e.g. grazing or trampling of vegetation, clearing forests)


Definition of conservation

The maintenance of biodiversity through human action or management


Definition of preservation

The protection of an area by restricting or banning human interference, so that the ecosystem is kept in its original state.