AS91157 - NCEA Level 2 Biology
Monohybrid Cross
A cross between two individuals, concentrating on only one definable trait
Zygote
A fertilized egg
Sex-linked
A gene located on a sex chromosome
Substitution
A mutation in which a nucleotide or a codon in DNA is replaced with a different nucleotide.
Neutral Mutation
A mutation that has no effect on the organism
Beneficial Mutation
A mutation that increases fitness of the organism, or which promotes traits that are desirable
Harmful Mutation
A mutation that reduces an organisms fitness
Chromosome Mutation
A permanent change in a section of a chromosome
Gene Mutation
A permanent change in the number of chromosomes
Gene
Section of DNA that codes for an amino acid sequence
Segregation
Separation of alleles during gamete formation
Co-dominance
Situation in which both alleles of a gene contribute to the phenotype of the organism
Dominant
Will show in the phenotype if present
Sex Determination
XX for female, XY for male
Centromere
Central part of a chromosome where two chromatids are joined
Evolution
Change in a kind of organism over time; process by which modern organisms have descended from ancient organisms
Mutagen
Chemical or radiation that cause a mutation in the DNA
Somatic Autosome
Chromosome not concerned with gender
Independent Assortment
Chromosomes are distributed in different combinations each time a sex cell undergoes meiosis
Gene Pool
Combined genetic information of all the members of a particular population
Dihybrid
Cross concerned with two characteristics
Monohybrid
Crossing of one characteristics
Base Pairs
Cytosine to Guanine, Adenine to Thymine
DNA
Deoxyribose Nucleic Acid
Sex Chromosome
Determines the gender - X or Y
Genome
Entire genetic make up or bases sequence of one organism
Non-disjunction
Error in meiosis in which homologous chromosomes fail to separate
Locus
Exact location of a gene
Crossing Over
Exchange of genetic information between two homologous chromosomes
Disruptive Selection
Form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle
Asexual Reproduction
Form of producing offspring without involving sex producing identical offspring
Migration
Form of relocation diffusion involving permanent move to a new location
Diploid
Full set of chromosomes eg 2N
Founder Effect
Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population
Homozygous
Genotype AA or aa
Hetero-zygous Dominant
Genotype Aa
Hetero-zygous Recessive
Genotype aa
Semi-conservative
Half old, half new
Haploid
Half the number of chromosomes eg 1N
Gametic Cell
In connection to sex cell or gametes
Bottleneck Effect
A change in allele frequency following a dramatic reduction in the size of a population
Genetic Drift
A change in the allele frequency of a population as a result of chance events rather than natural selection
Trait
A characteristic that an organism can pass on to its offspring through its genes
Natural Selection
A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits
Mutation
A random, permanent change in the DNA base sequence
Incomplete Dominance
A type of inheritance in which two contrasting alleles contribute to the individual a trait not exactly like either parent; blending inheritance
Stabilising Selection
A type of natural selection in which genetic diversity decreases as the population stabilises on a particular trait value
Genotype
Alleles present
Allele
Alternative forms of a gene
Somatic Cell
Body cells
Insertion
Causes a frame shift by adding a base, protein is affected
Deletion
Causes a frame shift by missing out one base, protein is affected
Duplication
Causes a frame shift by repeating a base or sets of bases, protein is affected
Mitosis
Cell division in body cells
Meiosis
Cell division in sex cell only
Pure Breeding
Individuals that are homozygous that will always produce the same offspring when crossed together
Centriole
Involved in cell division, in animals it produces spindle fibres
Emigration
Migration from a location
Immigration
Migration to a new location
Translocation
Moving a base or a number of bases to a different location, protein could be affected
Directional Selection
Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals
Allele Frequency
Number of times that an allele occurs in a gene pool compared with the number of alleles in that pool for the same gene
Recombinants
Offspring whose phenotype differs from that of the parents
Chromatid
One 'arm' of a chromosome
Recessive
Only expressed if homozygous
Non-recombinants
Parental types, offspring shows the same traits as parents
Phenotype
Physical appearance of the offspring
Chiasma
Point of crossing over
Histone
Protein around the DNA
Chromosome
Structure made of DNA
Nucleotide
Subunit of the DNA
Recombination
Swapping of alleles during meiosis
Test Cross
Test to see if the individuals are homozygous or heterozygous
Fertilisation
The fusion of 2 [haploid] gametes to form a [diploid] zygote
Homologous Pair
Two chromosomes with the same genes but could have different alleles
Heritable Variation
Variation that is passed on to offspring
