Patterns of Inheritance 6.2 Flashcards
What are three types of mutagens(something capable of inducing mutations)?
1.Physical agents e.g. x-rays
2.Chemical agents
3.Biological agents e.g some viruses
What are mutagens?
-Mutagens are something that increase the rate of mutation
What are Chromosome mutations that may occur during meiosis?
-Deletion: part of chromosome is lost
-Inversion: section of chromosome breaks off and rotates 180 degrees then rejoins
-Translocation
-Duplication
-Non-disjunction (Definition on another card)
-Aneuploidy ()
-Polyploidy (*)
What is non-disjunction, Aneuploidy and Polyploidy?
-Non-disjunction: one pair of chromosome fails to separate leaving the zygote with an extra chromosome
-Aneuploidy: the chromosome number is not right for the haploid of that animal
-Polyploidy: a diploid gamete fertilises a haploid gamete resulting in a triploid zygote
What is etiolation?
Etiolation: plants grow abnormally long and spindly due to lack of light
How does genetic variation arise during meiosis?
-Allele shuffling during crossing over in prophase 1
-Independant assortment of chromosomes in metaphase/anaphase 1
-Independant assortment of chromatids in metaphase/prophase 2
What is meant when a characteristic is said to be monogenic?
-The characteristic is determined by one gene with two distinct alleles
What is Mendels test cross for monogenic inherritance?
1.The organism with the dominant phenotype for example tall pea plant (so its genotype could be TT or Tt) is crossed with the organism expressing the recessive characteristic (small pea plant tt)
2. If any of the offspring have the recessive phenotype the orrganism expressing the dominant phenotype must be heterozygous (Tt)
What is a dihybrid cross?
-An investigation that examines the inherritance of two characteristics simultaneously
What is codominance and mutliple alleles?
-Codominance: where both alleles present in the genotype of a heterozygous individual contribute to the phenotype for example: Blood groups
-Multiple alleles: characteristic for which there are three or more alleles at a gene locus
What are sex-linked characteristics in humans and how are they caused?
-Haemophilia A and colour blindness
-When there is mutated alleles on the sex chromosomes these characteristics can be displayed
What is autosomal linkage?
-When gene loci are present on the same autosome (non-sex chromosome) so are often inherrited together
What is a recombinant gamete?
-When two autosomly linked genes cross over during meosis 1 creating unexpected phenotypes (recombinant phenotypes)
How does the distance between gene loci affect the chance of recombinant gametes forming?
-The larger the distance the greater chance of crossing over occuring and a recombinant gamete forming
What is epistasis and dominant and recessive epistasis?
-Epistasis: when one non-linked gene masks the expression of another gene
-Dominant epistasis: When the prescence of one dominant gene(or both) on one gene loci prevents the expression of another gene loci
-Recessive epistasis: when the prescence of a homozygous ressesive gene allele prevents the expression of a gene at a second locus
What is the equation for the Chi squared test?
O: each observed number
E: each expected number
-Expected numbers can be found by doing a punnet square and working out a ratio
How do you carry out a Chi squared test and what is it used for?
-The chi squared test is used to determine wether our observed results are different to our expected results due to chance
1.State null hypothesis(There is no statistically difference between data and any difference is due to chance)
2.Calculate a value for x^2
3.Determine the degrees of freedom (number of categories-1)
4.Determine a value for P and if x^2 is less than then any difference is due to chance, if it’s greater than difference is not due to chance, reject null hypothesis
What is continous and discontinous variation?
-Continous variation: is where the variation is distributed on a continuum
-Discontinous variation: is where the variations are placed onto discrete individual categories
What is interspecific and intraspecific variation?
-Interspecific variation: variation between individuals of the same species
-Intraspecific variation is variation between different species
What is stabilising selection?
-Usually occurs when the organisms environment remains unchanged
-Leads to constancy within a population, intermediate phenotypes are favoured and extreme phenotypes are selected against
-Genetic variation is reduced
What is directional selection?
-A type of natural selection which occurs when there is an enviromental change, the change favours a new phenotype and results in a change in the population mean
What is a genetic bottleneck?
-When a population size shrinks then increases again
-The genetic diversity will be reduced and some advantageous alleles will be removed putting the population at risk, if the size is so small fertillity can be affected
-However if the organisms that survive did so because of an advantage it can increase the gene pool of the population while still decreasing genetic diversity.
What is the founder effect?
-When a small sample of an original population establishes in a new area, and its gene pool is therefore not as diverse as the parental population
-So they are likely to lose genetic variation
What does a species need in order to survive and not become extinct?
-The species need genetic variation between the individuals in its population
What is the hardy-Weinberg principle equations?
P^2+2PQ+Q^2=1
p+q=1
What are the assumptions of the Hardy-Weinberg principle?
1.Population is large enough to make sampling error negligible
2.Mating within the population occurs at random
3.There is no selective advantage for any genotype
4. there is no mutation, migration or genetic drift
What are sub-species?
-When two populations are different but still able to interbreed they are said to be sub-species
What is speciation?
-When a genetically identical population is split into two or more, and the populations undergo genetic differentiation leading to the evolution of two species that can’t reproduce to produce fertile offspring
What is allopatric and sympatric speciation?
-Allopatric speciation: formation of two species from an original species due to geographical isolation e.g lakes acting as barriers
-Sympatric speciation: formation of two species from an original species due to reproductive isolation e.g a mutation that changes the time of year individuals mate despite being in the same geographical location
What is artificial breeding and how can it lead to an inbreeding depression and problems?
-Artificial breeding: selective breeding of organisms, involving humans choosing the desired phenotypes and interbreeding them.
-As individuals only with desirable characteristics are chosen, genetic diversity of gene pool is reduced and chances of inbreeding related individuals increases (inbreeding depression), also as individuals are genetically similar a pathogen is more likely to kill whole population
What are the ethical considerations of artificial selection?
-Livestock are less likely to survive for e.g during winter due to less fat
-Domestic animals e.g pets can’t defend themselves from predators due to for e.g fur colour which looks nice but can’t camoflauge
