chapter 9 Flashcards
gene pool
All the genes and alleles in a population at a particular time
Non- disjunction
when chromosomes or chromatids do not split equally during anaphase
polyploidy
type of chromosome mutation where there are changes to the whole set of chromosomes occur when organisms have 3 or more sets of chromosomes rather than the usual 2
aneuploidy
type of chromosome mutation where there is a change in the number of individual chromosomes
what is meiosis
cell division creates genetically different gametes, 4 haploid daughters cells are produced
haploid (n)
one copy of each chromosomes
diploid (2n)
two copies of each chromosomes
genetic diversity
the number of different alleles in a population
evolution
changes in allele frequency over many generation
gene mutation
change in the base sequence of DNA
mutagenic agent
factor the increases rate of mutation
chromosome mutation
random changes in the number of chromosomes caused by chromosome non-disjunction during meiosis
2 reasons why gene mutations may not cause change to the primary structure of a protein
1- the genetic code is degenerate, so the new triplet of bases may still code for the same amino acid
2- if the mutation occurs in an intron
describe crossing over
pair of homologous chromosomes associate with each other, creates a chiasma, this causes tension in the chromatid causing them to break off, broken chromatids recombine with one another
independent segregation
homologous pairs of chromosomes line up opposite each other at the equator, the side where they line up is random, pairs separate so one from each pairs ends up in a daughter cell, creates number of combination
natural selection
- New alleles that increase genetic diversity created by random mutation
- If the new alleles increase the chances of the individual to survive in that environment, then they are more likely to survive and reproduce
- The reproduction passes on the advantageous allele to the next generation
-As a result, over many generation the new allele increase in frequency in the population - Other alleles decrease in frequency
stabilizing selection
mean trait has the advantage
there’s no change in the environment
mean trait is not changed
standard deviation decreases as individuals with extreme traits decrease
directional selection
one of the extremes has the selective advantage
only occurs when there’s a change to the environment
mean trait changes
advantage of natural selection
it results in species becoming better adapted to their environment
