Classical Genetics Flashcards
Law of Dominance
When 2 organisms, each homozygous (pure) for 2 opposing traits are crossed, the offspring will be hybrid (carry out 2 different alleles) but will exhibit only the dominant trait
Trait that remains hidden = recessive trait
Law of Segregation
When an organism makes gametes, each gamete receives just 1 copy, which is selected randomly
Monohybrid cross
A cross between 2 organisms that are each hybrid for a single trait
(Tt x Tt)
Genotype
Type of gene
The set of genes in DNA which is responsible for a particular trait
Genes responsible for: eye colour, height, shoe size
Phenotype
What an organism looks like
The visible expression/characteristics of that trait
Visible characteristics for; eye colour, height, shoe size
Backcross (Testcross)
A technique to determine whether an individual plant or animal showing the dominant trait is homozygous dominant (BB) or heterozygous (Bb)
Incomplete Dominanc
An inheritance pattern characterised by blending of traits
Black animal cross with white animal = grey offspring
Law of Independent Assortment
A cross that is carried out between 2 individuals hybrid for 2 or more traits that are not on the same chromosome
Resulting phenotype ratio: 9:3:3:1
Codominance
When the alleles of a gene are expressed equally & neither is dominant or recessive
Blood type; A & B -> AB
Multiple Alleles
When there are more than 2 allelic forms of a gene
Humans, more than 2 alleles for blood type
Polygenic
More than 2 allelic forms of a gene, like height or colour, the trait exhibits a multitude of variation
Two short parents -> tall offspring
Sex-Linked
Traits that are carried on the X chromosome
Recessive traits: colour blindness, haemophilia
Sex-Influenced Trait
Inheritance is influenced by sex of individual carrying the traits
Baldness
Karyotype
Procedure that analyses the size, shape, & number of chromosomes
During metaphase of mitosis
Pedigree
Family tree that indicates the phenotype of 1 trait being studied for every member of a family
Used to determine how a particular trait is inherited
Mutation
Any change in a gene or chromosome, when/where mutations occur is random
Gene Mutations
Caused by a change in the DNA sequence
Chromosome Mutations
Chromosome may sustain a deletion/addition, or cell may have an entirely extra chromosome which results from nondisjunction
Nondisjunction
An error that sometimes happens during meiosis in which homologous chromosomes fail to separate as they should
Aneuploidy
Any abnormal condition of the chromosomes
Deletion
A fragment lacking a centromere is lost during cell division
Inversion
A chromosomal fragment reattaches to its original chromosome but in the reverse orientation
Translocation
A fragment of a chromosome becomes attached to a non-homologous chromosome
Polyploidy
A cell/organism that has extra sets of chromosomes
Often plants or flowers
Gene
Heritable factor that controls a specific characteristic
Allele
1 specific form of a gene, occupying the same gene locus as other alleles of the gene
Genome
The whole of the genetic information of an organism
Homologous Chromosomes
Chromosomes that have the same structural features & the same genes
Dominant Allele
An allele that is expressed in the phenotype in a homozygous or heterozygous state
Recessive allele
An allele that is only expressed in the phenotype in a homozygous state
Codominant Alleles
A pair of alleles which both affect the phenotype in a heterozygous
Homozygous
Having 2 identical alleles of a gene
Heterozygous
Having 2 different alleles of a gene
Carrier
A heterozygote who has 1 copy of a recessive allele that causes a genetic disease
Autosome
Any chromosome that is not a sex linked chromosome
