heredity - genetic variation Flashcards
How can the genetic similarities and differences within and between species be compared?
comparative analysis techniques → DNA hybridisation and DNA sequencing
Within a species, → alleles can be tracked through analysis of pedigrees and specific test crosses.
More modern projects → genome mapping, and technologies identifying SNPs
somatic mutation
A mutation that occurs in a ‘body cell’ and is not passed on to offspring.
gametic mutation
A mutation that occurs in a sex cell and is heritable.
substitution nonsense mutation
A change in one DNA base pair. Instead of substituting one amino acid for another the altered DNA sequence signals the cell to stop building a protein.
frameshift deletion mutation
An deletion of a nucleotide that shifts the sequence. → large sale changes in amino acid sequence → nonfunctional protein
silent mutation
A form of point mutation that results in a codon that codes for the same amino acid.
missense mutation
A change in one DNA base pair that results in the substitution of one amino acid for another in the resulting polypeptide.
heterozygous
containing two different alleles for a trait
when is a recessive allele expressed
only expressed in the phenotype when the genotype is homozygous
dominant allele
always expressed in phenotype
homozygous
containing the same alleles for a trait
sex-linkage
genes present on sex chromosomes rather than non-sex chromosomes
co-dominance
type of inheritance where who alleles of the same gene are expressed separately to yield different traits in an individual
RR + rr can only = Rr = new variation
incomplete dominance
both alleles are partially expressed → intermediate or different phenotype
multiple alleles
traits controlled by a single gene with more than two alleles e.g. blood type
