Genes and Patterns of Inheritance Flashcards
Who is Gregor Mendel and what are his 3 conclusions from his experiments?
He did experiments with pea plants because he was able to control the fertalization, and his three experiments were traits are dominant and recessive, genes versus alleles (a gene has two variant forms, or alleles), and lastly the segregation of alleles.
Define locus, genes, alleles and linked genes.
Locus: a term that tells where on a specific chromosome a specific gene is.
Gene: The basic physical and functional unit of heredity
Alleles: alternative form of gene that is located at a specific position on a specific chromosome.
Linked genes: genes that are on the same chromosome.
Describe homo- and heterozygous and give examples.
Homozygous means there would be the same gamete, so TT or tt. TT would be homozygous dominant and tt would be homozygous recessive. Heterozygous would be Tt (two different gametes).
Define genotype and phenotype.
Genotype is the genetic composition (what is there), and phenotype is the physical expression (what you see).
Autosomal recessive traits
appear equally in males and females and tend to skip generations. (Cystic fibrosis)
Autosomal dominant traits
appears equally in males and females and unaffected persons do not transmit the trait. (Huntington’s disease)
X-linked recessive traits
appear more frequently in males and located on the X chromosome. (Color blindness)
X-linked dominant traits
does not skip generations and affected males pass on to daughters but not sons. (Rett syndrome)
Describe monohybrid cross- what is required and what are the pheno- and genotypic ratios?
Two individuals with homozygous genotypes are needed and the genotype ratio is 1:2:1, and the phenotype ratio is 3:1.
Describe dihybrid cross- what is requires and what are the pheno- and genotypic ratios?
Two individuals with heterozygous or different traits are needed, and the genotype ratio is 1:2:1:2:4:2:1:2:1, and the phenotype ratio is 9:3:3:1.
Define and describe incomplete dominance, codominance,and pleiotropy.
-Incomplete dominance: this occurs when the heterozygote has a phenotype intermediate to the phenotypes of the homozygotes.
-Codominance: This occurs when the heterozygote expresses both alleles simultaneously.
-Pleiotropy: a mutation in a single gene can have multiple effects on an individual’s phenotype.
Describe sex-linked genes.
Found in many (but not all) species with two sexes, X-Y system (mammals), X-O system (insects), Z-W system (birds).
Define epistasis and give an example.
A type of gene interaction in which the alleles of one gene mask the effects of an allele of another gene. (a colorless precursor molecule must be acted upon by two different enzymes to produce purple pigment).
