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