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
alleles frequency
alleles in homozygous individuals + alleles in heterozygous individuals
divided by the amount of alleles in the population
single nucleotide polymorphism (SNP)
a point mutation in a segment of DNA that occurs in more than 1% of the population → found in introns (between genes) → little effect on cellular function
SNPs act as chromosomal tags to specific regions of DNA, and these regions can be scanned for variations that may be linked to diseases or disorders.
