Patterns of Inheritance Flashcards
Gregor Mendel
Pea plant experiment
Genotype
Genetic makeup
-describes all the alleles that an organism has
Phenotype
Visual characteristic of an organism
due to genotype and environment
Alleles
Different forms of a gene
eg different eye colour
Physical mutagens
X-rays, gamma rays & UV
Chemical mutagens
Benzopyrene - tobacco smoke
Biological mutagens
Viruses and food contaminants
Codominance
Blood groups
where 2 different alleles both contribute to the phenotype displayed
blend of both features
Genetic causes of variation
Indel
Inversion
Translocation
Non disjunction (polyploidy&aneuploidy)
hardy weinberg calculation
p2 + 2pq + q2 = 1
p + q = 1
what each letter means
p = frequency of dominant allele
q = frequency of recessive allele
p2 = % of homozygous dominant
q2 = % of homozygous recessive
2pq = % of heterozygous individuals
discontinuous variation
individuals fall into a number of distinct classes/ categories
qualitative differences
-bar charts
-blood groups
-monogenic
continuous variation
complete range of measurements from one extreme to another
-no definite categories
-quantitative differences
-line graph, polygenic
chi squared
x2 = sum of (O-E)2 / E
finds out whether the difference is due to chance or a real effect
critical value found
uses degrees of freedom = n-1
then 0.05
if value is bigger than table reject null hypothesis
if lower than table accept
how can meiosis bring about genetic variation
Random arrangement of chromosomes lining up
Crossing over of chromatids before first division
monogenic inheritance
when one phenotypic characteristic is controlled by a single gene
dihybrid inheritance
where 2 phenotypes are determined by 2 different genes present on 2 different chromosomes at the same time
sex linkage
where an allele is located on one of the sex chromosomes
meaning its expression depends on the sex of the individual
multiple alleles
a gene with more than 2 alleles
Xo Xa
eg blood groups
autosomal linkage
where 2 or more genes are located on the same (NON SEX) chromosome
one homologous pair needed for all 4 alleles to be present
if not linked 2 homologous pairs needed
epistasis
where 2 non linked genes interact and one masks the the expression of the other
eg black in colour but melanin gene not produced so the animal is white albino
stabilising selection
occurs when environmental conditions stay the same
individuals closest to mean are favoured
any new characteristics are selected against
-low diversity
Directional selection
Occurs when environmental conditions change
individuals with phenotypes suited to new conditions will survive and pass of their genes
over time mean of population will move towards these characteristics
genetic drift
change in a populations allele frequencies that occurs due to chance
genetic bottleneck
catastrophic event occurs reducing size of population
decreasing variety and diversity
founder effect
when a small number of individuals become isolated and create a new gene colony
limited gene pool
speciation
where a population is split and isolated
different selective pressures on 2 groups
2 groups can no longer interbreed if genetic makeup is changed to an extent
allopatric speciation
speciation resulting from a physical barrier geographic
sympatric speciation
speciation from a non physical barrier
eg a mutation that means the 2 individuals can no longer produce fertile offspring
artificial selection
when humans pick the individuals to breed to produce desired offspring
