Pack 19 - Variation of Population Genetics Flashcards
how is there variation due to genetic factors?
when characteristics of individuals in a population fall into a limited number of distinct forms, with no intermediates
only one or two genes act
during meiosis, mutations or random fusion of gametes
how is there variation due to environmental impacts?
when extreme features are controlled by genetics can be greatly influenced by the environment
some factors include diet, temperature and light intensity
What does genotype + environment =
the phenotype
how does meiosis lead to variation?
independent segregation (when the maternal and paternal chromosomes split into haploid cells) crossing over (crossing over of genetic material from similar chromosomes)
how does the random fusion of gamete lead to variation?
due to it being a random process it produces new combinations of alleles and the offspring therefore will be gentically different from the parents
how does a mutation cause variation?
causes a change in the number or sequence of bases in the DNA
produces a change in characteristics of the organism
what are the different types of mutation?
Addition/Deletion Substitution Duplication of Bases Inversion of Bases Translocation of Bases
what happens during addition/ deletion?
an extra base is added or removed in sequence
changes all subsequent triplets (completely different amino acid sequence is made)
known as frame shift
what happens during substitution and what are the 3 consequences?
one base is swapped for another
meaning an amino acid in polypeptide chain could change and cause tertiary structure to fail (missense mutation)
base could result in stop codon forming so translation of polypeptide stops early (nonsense mutation)
could cause no difference as the same amino acid could be coded for (silent mutation)
what happens in the duplication of bases?
one or more bases are inverted which then makes frameshift occur (addition/deletion) to the right
what happens during the inversion of bases?
when a group of bases get separated from the DNA and rejoin at the same position but in an inverse order
what happens during the translocation of bases?
group of bases become separated from the DNA and become inserted into the DNA sequence of the same or a different chromosomes
what can you use to calculate expected frequency of alleles?
The Hardy- Weinberg equation
what is the Hardy- Weinberg equation?
p^2 + 2pq + q^2 = 1.0
p = frequency of dominant allele q = frequency of recessive allele p^2 = homozygous dominant genotype q^2 = homozygous recessive genotype 2pq = heterozygous genotype
what is genetic drift?
the idea that allele frequency can change due to chance
