Topic 9- Key Terms Flashcards
Define Genetic Diversity
Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species
Define Mutations
A permanent, heritable change in the nucleotide sequence in a gene or a chromosome; the process in which such a change occurs in a gene or in a chromosome
Define Substitution
It is a mutation that exchanges one base for another
Define Deletion
It is a mutation in which a part of a chromosome or a sequence of DNA is lost during DNA replication. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome.
Define A Frameshift
It is a genetic mutation caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence that is not divisible by three.
Define Chromosome Mutations
These mutations can involve deletions, additions, or inversions substitutions of sections of DNA.
Define The Term Polyploidy
It is the state of a cell or organism having more than two paired (homologous) sets of chromosomes
Define Homologous Chromosomes
A homologous pair is a pair of chromosomes containing a maternal and paternal chromatid joined to together at the centromere. They have the exact same gene - although may have different alleles of these genes
Define Gene Pool
The total number of alleles in a particular population at a specific time.
Define Meiosis
The type of nuclear division in which the number of chromosomes is halved
Define The Diploid Cell
A cell containing homologous pairs of chromosome (maternal and paternal). The diploid number for humans is 46.
Define The Haploid Cell
A cell containing one complete set of chromosomes. The haploid number for humans in 23.
Define Locus
A fixed position on a particular DNA molecule occupied by a gene
Define Gene
The base sequence of DNA (along the chromosome) that codes for the amino acid sequence of a polypeptide or functioning RNA.
Define Sister Chromatid
One-half of a chromosome that has undergone semi-conservative DNA replication
Define Allele
One of the different forms of a gene
Define Genetic Variation
Variation describes differences in the genetic make-up between individuals within a species
Define Crossing Over
The process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosomes so their alleles are exchanged.
Define Independent Segregation
Is due to the random orientation of pairs of homologous chromosomes in meiosis I
Define Phenotype
Refers to the observable physical properties of an organism; these include the organism’s appearance, development, and behavior.
Define Directional Selection
Is a force in nature that causes a population to evolve towards one end of a trait spectrum
Happens when the environment changes
Define Stabilising Selection
Which the population mean stabilizes on a particular non-extreme trait value.
When the environment stays the same
Define Selection Pressure
Any cause that reduces reproductive success in a portion of a population
Define Genotype
The set of genes the organism carries, as well as by environmental influences upon these genes.
Define Gamete
The reproductive cell that fuses with another gamete of the opposite sex during fertilization
Define Gene Mutations
A permanent alteration in the DNA sequence that makes up a gene
Define Non-Disjunction
Refers to the chromosomes failing to separate correctly, resulting in gametes with one extra or one less chromosome
Define Recombination
A process by which pieces of DNA are broken and recombines to produce new combinations of alleles creates genetic diversity
Define Species
A group of similar organisms that can breed together to produce fertile offspring
Define Allele Frequency
Refers to how frequently a particular allele appears in a population
Define Polygenes
Refers to a group of genes that when expressed together produce a particular phenotype or trait
Define Normal Distribution Curve
A theoretical frequency distribution for a random variable characterized by a bell-shaped curve.
