Mr G bio 3 genes, alleles and inheritance Flashcards
what is a gene?
sequence of bases on a DNA molecule that code for a polypeptide which results in characteristics
what are alleles?
different versions of the same gene
what is a locus?
fixed position of the allele of each gene
what is a genotype?
an organisms genetic constitution
what is a phenotype?
the expression of the genetic constitution and its interactions with the environment
what are codominant alleles?
both alleles are expressed in the phenotype because neither one is recessive
what is dihybrid inheritance?
inheritance of two characteristics, which are controlled by different genes. each of the two genes will have different alleles
why will you not always get the 9:3:3:1 ration with 2 heterozygous parents?
gene linkage, epistasis, lethal genotypes, small sample size, random fusion of gametes
what are sex-linked characteristics?
means the allele that codes for the characteristic is located on the sex chromosome
why are males more likely to show recessive phenotpyes for genes that are sex-linked?
males only have one X chromosome so they often only have one allele for sex-linked genes and because they only have one allele for sex-linked characteristics, they express the characteristic of this allele even if recessive
what is an autosome?
the name for any chromosome that isnt a sex chromosome
what is the name for genes located on the autosomes?
autosomal genes
what is linkage?
genes at different loci on the same gene that (except for crossing over) tend to be inherited together
why are genes on the same autosome said to be linked?
because theyll stay together during the independent segregation of chromosomes in meiosis 1 and alleles be passed on to the offspring together (might not happen if crossing over occurs)
how can you tell how closely related two autosomal genes are?
the closer together the two genes are on the autosome, the more closely they are said to be linked (crossing over less likely to split them)
