9.0 Genetic Diversity Flashcards
What is a gene mutation?
A change to the DNA base sequence
What is the difference between a substitution and deletion mutation?
A substitution mutation results in the
replacemnet of one base for another whereas a
deletion involves the removal of a base and
results in a frame shift mutation
Why is a deletion mutation commonly more dangerous?
Causes a frameshift mutation and cuases all
triple codes after the mutation to change
resulting in different amino acids and the protein
not being produced
What is a polyploidy?
When organisms have three of more sets of each
chromosome.
What is non-disjunction of chromosomes?
When the individual homologous pairs fail to
separate during meisois and resulting in a gamete
having one more or one less chromosome than it
should have
Explain why errors I DNA replication can be more damaging than errors to transcription?
An error to DNA replication will be passed down
to all daughter cells. Whereas an error in
transcription only affects that single mRNA
transcript and more can easily be produced.
Explain why a mutation that is transcribed onto mRNA may not result in any change to the polypeptide sequence?
Because the change is in introns that are
removed or because the genetic code is
degenerate
What happens in crossing over?
The chromatids of each pair wrapa round each
other. This tension causes portions of the
chromatids to break off. These broken portions
can be rejoined on its homologous partners. The
areas this occurs at is called a chiasmata.
Is a cell with 27 chromosomes likely to be haploid or diploid?
Haploid because it is is a odd number
What is the difference between anaphase I and II?
In anaphase II the centromeres break down and
allows chromatids to be seperated
What is independent assortment?
The homologous chromosomes line up randomly
at the the equator., the combination of
chromosomes of maternal and paternal origin
that pass to the offspring are random
What is genetic diversity?
Total number of different alleles in a population
What is stabilising selection?
Favours average individuals. Characteristics at the
middle of the range
Individuals with alleles for characteristics towards
the middle of the range are more likely to survive
and reproduce
Favours average individuals
Individuals with alleles for characteristics towards
the middle of the range are more likely to survive
and reproduce
Favours average individuals
Individuals with alleles for characteristics towards the middle of the range are more likely to survive
and reproduce
What is directional selection?
Favours individuals at the extremes of the range
Give an example of stabilising selection
Birth weight
