Genetic Variation Flashcards
Asexual
reproduction
Reproduction involving only one parent. Doesn’t produce genetic variation.
Allele Frequency
The number of each allele in a population or a gene pool.
Alleles
Alternative form of a gene (eg blue eyes or brown eyes)
Chiasma
Point of contact, the physical link, between two (non-sister) chromatids belonging to homologous chromosomes during crossing over
Crossing Over
Occurs during meiosis, when the homologous chromosomes line up at
the equator, and exchange genetic information. Leads to new combination of alleles.
Co dominance
When both alleles are equally dominant and both are expressed in the offspring if present.
Complete
dominance
A form of dominance where the allele that is regarded as dominant completely masks the effect of the allele that is recessive
Diploid
A cell or an organism consisting of two sets of chromosomes: usually, one set from the mother and another set from the father
Dominant Allele
An allele which is always expressed in the phenotype if it is present as it will mask any recessive allele.
Evolution
Is the change in the characteristics of a species over several generations and relies on the process of natural selection.
Fertilizations
A process in sexual reproduction that involves the union of male (sperm) and female (ovum) gametes (each with a single, haploid set of chromosomes) to produce a diploid zygote
Founder effect
when a small number of individuals from an existing population moves to another area and establishes a new population and it becomes reproducibly isolated from the original population.
Fitness
The ability of an individual to survive and reproduce.
Genetic Drift
Random change in allele frequency due to chance.
Genetic Variation
Is the differences or the diversity in the genetic makeup in a population
Gamete
Sex cell of an organism e.g. sperm, egg, pollen or ova. A haploid sex cell.
Genotypic Ratio
A ratio showing the probability off the offspring in a particular cross having a possible phenotype.
Gene
A length of DNA that holds the instructions for a characteristic. A sequence of bases (in DNA) that code for a particular trait
Gene pool
The total alleles in a population.
Gene Flow
is the movement of alleles in-between populations. This increases genetic variation in a population but decreases variation between population.
Genotype
The genetic make-up of the organism
Haploid
When a cell has half the usual number of chromosomes.
Heterozygous
Different forms of the allele are present in the genotype e.g. Hh. Used to describe an individual with two different alleles for a trait.
Homozygous
Used to describe an individual that has two identical alleles for a trait.
Incomplete Dominance
Neither allele is completely dominant so when both alleles are present, two new phenotypes blend to create a new distinct phenotype
Homologous Chromosomes
Chromosome pairs (one from each parent) that are similar in length, However, the genes may contain different alleles.
Homozygous
The same form of the allele is present in the genotype e.g. HH
Independent Assortment
When homologous chromosomes line up at the center of they cell, they do so independently of all the other pairs.
Lethal Alleles
The presence of an allele in the genotype of an organism that leads to the death of that organism. Ratios change from 3:1 ot 2:1
Linked Genes
Genes located on the same chromosome that tend to be inherited
together
Meiosis
Cell division to create the four haploid gametes which are different from each other and from the original cell.
Migration
Movement of individuals into (immigration) and out (emigration)of a
population
Multiple Alleles
When three or more alternative forms of a gene (alleles) that can occupy
the same locus. e.g. ABO blood types
Mutation
A permanent change in the base sequence of DNA. This change is ireversible. Mutations introduce genetic variation in a population. Only way to create new alleles.
Natural Selection
The process of selecting individuals with favorable alleles and selecting against unfavorable alleles. Those individuals with favorable alleles survive, reproduce and pass on their alleles to their offspring whereas the individuals selected against would be removed from the population. This process reduces genetic variation in a population
Pedigree chart
Is a diagram that depicts the biological relationships between
an organism and its ancestors
Phenotype
The physical appearance of the organism. The physical expression of the genotype.
Bottle Neck Effect
is the sudden, drastic reduction in allele frequency in a population due to natural disasters/ human introduction of predators.
Pure Breeding
A group of identical individuals that only produce one type of gamete due
to the fact they are homozygous
Population
a biological population is all members of one species that live in a defined area
Phenotypic Ratio
A ratio showing the probability of the offspring of a particular cross having each possible phenotype.
Recessive Allele
An allele that will only be expressed if there is no dominant allele to mask it
Segregation
The process that occurs during meiosis where pairs of alleles are
separated when the homologous chromosomes split
Selective Pressure
Can take many forms, including environmental conditions, availability off food and energy sources, predators, diseases, and even direct human influence. The selective pressure means that animals that don’t have these characteristics are less likely to survive and reproduce due to natural selection.
Sexual Reproduction
Reproduction in which one gamete from each of two individuals combine to form a new individual. Produces Genetic variation.
Somatic Cells
Body Cells
Sister Chromatids
Two identical copies of a chromosomes, created by DNA replication. The sister chromatids are stuck together by a cellular glue.
Test Cross.
A genetic cross between a homozygous recessive individual and a
corresponding suspected heterozygote to determine the genotype of the latter.
