Topic 6: Key words A-Z

Question 1

Allele

Answer 1

A version of a gene

Question 2

Allopatric speciation

Answer 2

Specialisation that occurs when two populations become geographically isolated due to a physical barrier

Question 3

Apoptosis

Answer 3

Programmed cell death

Question 4

Autosomal linkage

Answer 4

2 or more genes are positioned on the same autosome. They are often inherited together as they are unlikely to be separated by crossing over in meiosis.

Question 5

Autosome

Answer 5

A chromosome that is not an X or Y chromosome

Question 6

Codominance

Answer 6

Both alleles for a gene in a heterozygous organism equally contribute to the phenotype

Question 7

Continuous variation

Answer 7

Variation where there is no clear separation into distinctive categories (e.g height). It produces a continuous range where. a characteristic can take any value. Multiple genes influence it.

Question 8

Deletion mutation

Answer 8

A nucleotide base is removed from a DNA sequence. This may lead to a frameshift mutation, triplets downstream will be different

Question 9

Dihybrid inheritance

Answer 9

Inheritance of two genes determines a trait

Question 10

Directional selection

Answer 10

Natural selection that produces a gradual change in allele frequencies over several generations.
Happens when there is a change in selection pressures or a new allele has appeared in the population that is advantageous

Question 11

Discontinuous variation

Answer 11

Variation that can be categorised e.g blood group. Appears only in discrete vales. One or two genes influence it.

Question 12

Disruptive selection

Answer 12

A type of selection that favours individuals with extreme phenotypes and selects against those with phenotypes close to the mean.

Question 13

DNA ligase

Answer 13

Enzyme that joins the sugar phosphate backbone of two DNA segments

Question 14

DNA profiling

Answer 14

Technique used to determine the patterns in a non coding DNA of an individual, where unique repeating patterns can be used to differentiate one person from another.

Question 15

DNA sequencing

Answer 15

Determining the entire DNA nucleotide base sequence of an organism

Question 16

Electrophoresis

Answer 16

A type of chromatography that separates nucleic acid fragments or proteins by size using an electric current.

Question 17

Electroporation

Answer 17

An electric current is used transfer recombinant plasmids into the bacterial cells or fragments of DNA into eukaryotic cells

Question 17

Electroporation

Answer 17

An electric current is used transfer recombinant plasmids into the bacterial cells or fragments of DNA into eukaryotic cells

Question 18

Epistasis

Answer 18

Relationship between genes at different loci, where the allele of one gene effects the expression of a different gene

Question 19

Evolution

Answer 19

The gradual change in allele frequency within a population over time, due to natural selection

Question 20

Exon

Answer 20

A sequence of DNA that codes for an amino acid sequence

Question 21

Founder effect

Answer 21

A type of genetic drift in which a few individuals of a species break off from the population and form a new colony. This results in a smaller gene pool and an increased frequency of rare alleles.

Question 22

Gene mutation

Answer 22

A change to at least one nucleotide base in DNA or the arrangement of bases. Occur spontaneously during replication.

Question 23

Gene therapy

Answer 23

A faulty allele is replaced with a functional allele to prevent or treat a disease

Question 24

Genetic bottleneck

Answer 24

​A drastic reduction in population size leading to reduced genetic diversity within a population.

Question 25

Genetic drift

Answer 25

Random variations in allele frequency in small populations due to mutations

Question 26

Genetic engineering

Answer 26

Modification of a genome of an organism by the insertion of a desired gene from another organism, enabling the formation of organisms with desired characteristics

Question 27

Genotype

Answer 27

An organisms genetic composition, describing all alleles

Question 28

Germ line cell gene therapy

Answer 28

A type of gene therapy in which the faulty allele is replaced with a functional allele in germ cells or a very early embryo, the effects are permanent and can be inherited.

Question 29

Homeobox genes

Answer 29

A group of regulatory genes that contain a DNA sequence that is highly conserved in animals, plants and fungi. Responsible for the development of body plans in different organisms

Question 30

Insertion

Answer 30

A form of gene mutation in which one or more nucleotide bases are added to a DNA sequence. This may lead to a frameshift mutation, changing every successive codon.

Question 31

Intron

Answer 31

Non coding region of DNA

Question 32

Lac operon

Answer 32

​A group of three structural genes, lacZ, lacY and lacA, that are required for the
metabolism of lactose.

Question 33

Mature mRNA

Answer 33

mRNA that has been modified by having introns removed

Question 34

Monogenic inheritance

Answer 34

Determination of a trait by the inheritance of a single gene

Question 35

Mutagen

Answer 35

​A chemical, biological or physical agent that increases the rate of gene mutations above normal level.

Question 36

Operon

Answer 36

group of genes that are expressed together and controlled by the same regulatory mechanism

Question 37

PCR

Answer 37

Polymerase Chain Reaction - an in vitro technique used to rapidly amplify fragments of DNA

Question 38

Repressor protein

Answer 38

A protein that binds to the operator altering transcription rate.

Question 39

Restriction endonuclease

Answer 39

Enzymes that cut DNA molecules at recognition sequences, creating ‘stick ends’

Question 40

Somatic cell gene therapy

Answer 40

A type of gene therapy in which a faulty allele is replaced with a functional allele in affected somatic cells. The effects of this are temporary and cannot be inherited.

Question 41

Stabilising selection

Answer 41

Favours individuals with phenotypes close to the meaning selects against extreme phenotypes

Question 42

Sticky ends

Answer 42

The staggered cut formed by endonuclease in double stranded DNA

Question 43

Substitution mutation

Answer 43

​A form of gene mutation in which one nucleotide base is exchanged for another. This may change an amino acid or produce the same amino acid (due to the degeneracy of the genetic code).

Question 44

Sympatric speciation

Answer 44

speciation occurs in the absence of a geographical barrier. Random mutations may occur within the population which results in behavioural, mechanical, or temporal changes, which cause the organisms to become reproductively isolated.