genetic variation flash cards

Allele

Alternative forms of a gene

Asexual reproduction

producing offspring with 1 parent without sex

Centromere

Area where chromatids remain joined until nuclear division

Centriole

small cell structure that helps chromosomes separate during cell division, in animals it produces spindle fibres.

Chiasmata

points where chromosomes cross and swap DNA during meiosis.

Chromatids

The two strands of a replicated chromosome

Chromosomes

a long strand of DNA that carries genetic information

Crossing-over

Exchanging of parts of chromatids during meiosis

Diploid

full set of chromosomes (2n)

DNA

double helix strand of material that makes up chromosomes and codes for proteins

Evolution

The change in the allele frequency of a population

Founder effect

small group of organisms separate from larger population and starts a new population. Has less variation, and different frequencies from the original population.

Gametes

Sex cells – egg or sperm

Gene

section of DNA that codes for a protein or trait

Genetic drift

A random change in a population’s genes caused by chance.

Genetic engineering

Altering the genetic make-up of an organism

Genotype

Genetic make-up of an organism eg. Bb

Haploid

Having a single set of chromosomes

Homologous pairs

Pairs of chromosomes

Independent assortment

Each pair of homologous chromosomes sorted independently of the other pairs during meiosis

Meiosis

Cell division that produces sex cells

Mitosis

Cell division for growth and repair that produces identical cells

Mutation

permanent change in the base sequence of DNA.

Nucleotide

Building blocks of DNA, made up of a phosphate, sugar and base

Phenotype

Physical expressing of genes

Recombinant

new combinations of alleles that were not originally found in the parents. comes from the gametes produced as a result of crossing- over

Sex chromosomes

Chromosomes that determination of sex of the organism

Sex linked

Genes that are located on the sex chromosome, usually the X

Test cross

Mating with an unknown genotype with the homozygous recessive e.g. hh

Zygote

Fertilised egg

Nondisjunction

when chromosomes do not separate correctly, resulting in incorrect chromosome numbers.

Karyogram

A map of sorted chromosomes used to detect nondisjunction or sex of the child

Gene pool

The total alleles within a population

Segregation

The separation of the homologous pairs during metaphase I, so the gametes only have one of each pair

Natural selection

survival of the fittest where organisms with helpful traits are more likely to survive and reproduce

Haemophilia

A sex-linked disease where the blood cells are unable to clot

Incomplete dominance

Offspring show a genotype where neither allele is dominant eg. Pink flowers

Inheritance

The passing on of genetic information from one generation to the next

Co-dominance

When two different alleles are both expressed in the phenotype.

Lethal gene

a mutation in the gene essential for the development of life. cause an organism to die.

Multiple alleles

allele where more than two forms can fit at a locus on a chromosome

Sex determination

In humans XX = female XY = male

Trait

genetic feature

Bottleneck effect

When a population loses most of its individuals and genetic variation due to a sudden event.

Linked gene

genes located on the same chromosome

Allele Frequency

The proportion of a specific allele in a population

complete dominance

allele regarded as dominant completely masks the effect of the allele that is recessive