6.2 Patterns of Inheritance

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  • Created by: elbungay1
  • Created on: 09-05-19 18:52
What is a genotype?
The genetic makeup of an organism
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What is a phenotype?
Visible characteristics of an organism
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What is a mutagen?
A factor that increases the rate of mutation. Can be a physical agent (X-rays, gamma rays, UV light), chemical agents (tobacco smoke) or biological (viruses)
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What types of chromosomal mutations are there?
Deletion, Inversion, translocation (part breaks off and joins another chromosome), duplication and non-disjunction (chromosomes fail to separate leading to aneuploidy)
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What stages of Meiosis result in genetic variation?
Allele-shuffling between non-sister chromatids in prophase 1. Independent assortment of chromosomes during metaphase/anaphase 1&2
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Give an example of Variation causes solely by the environment?
Speaking with a particular regional dialect. Losing a digit or limb, or having a scar following an injury
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What is an allele?
A variation of a gene
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What does heterozygous mean?
Not true-breeding; having different alleles at a particular gene locus on a pair of homologous chromosomes
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What does homozygous mean?
True-breeding. Having identical alleles at a particular gene locus on a pair of homologous chromosomes.
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What is the difference between monogenic inheritance and dihybrid inheritance?
Monogenic is a phenotype determined by a single gene. Dihybrid inheritance involves two gene loci
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What is the predicted ratio of phenotypes of F2 generation when a true breeding reccessive organism crosses with true breeding dominant in dihbyrid inheritance?
F1 generation will be completely TtRr. F2 generation will show a 9:3:3:1 ratio of phenotypes
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What are genes with multiple alleles and give an example?
Characteristic for which there are three or more alleles in population's gene pool. Example is human blood groups, with alleles IA, IB and IO
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What is a sex-linked gene?
A gene present one (one of) the sex chromosomes. Example is Haemophilia A in humans.
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What is codominance?
Where both alleles present in the genotype of a heterozygous individual contribute to the individual's phenotype. Therefore phenotype of heterozygotes is different from homozygotes. Example is AB blood group in humans
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What is autosomal linkage?
Gene loci present on the same autosome (non-sex chromosome) that are often inherited together
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What is epistasis?
Interaction of non-linked gene loci where one masks the expression of the other.
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What is the difference between recessive epistasis and dominant epistasis?
Recessive is when the presence of homozygous recessive allele at first locus masks expression of another allele at a second locus 9:3:4 ratio. Dominant is where presence of 1 dominant masks expression of other genes in codominance 13:3 ratio.
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What is a Chi-squared test used for?
Statistical test designed to find out whether the difference between observed and expected data is significant or due to chance
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Describe natural selection
Mutation and migration introduces new alleles into a population. Individuals in a population will be better adapted than others to environment, more likely to survive and reproduce, passing on advantageous alleles, altering allele frequency over time
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What is a stabilising selection?
Occurs when environment doesn't change and it favours intermediate phenotypes. E.g. babies of birth mass close to 3.5 kg are more likely to survive, offspring inherit these alleles also leading to this mean birth mass
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What is a directional selection?
If environment changes, optimum phenotype changes and becomes the ideal, this is selected for. Organisms with these genotypes more lilley to reproduce and over time there is a gradual shift in optimum value for the trait. e.g. cheetah speed.
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What is genetic drift?
When population descends from a small parent population, population will lack genetic variation. Mutation can drastically alter the allele frequency. Catastrophic event e.g. earthquake may remove alleles from existence.
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What is genetic bottleneck?
When population size shrinks and then increases again. After this event, genetic diversity within population will be reduced. May be loss of advantageous alleles or disproportionate frequency of harmful alleles. May be beneficial for disease resistan
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What is the founder effect
When a new population is established by a very small number of individuals. New population likely to exhibit loss of genetic variation. Special case of genetic drift
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What assumptions are made in Hardy-Weinberg Principle?
Population is large enough to make sampling error negligible. Matting occurs at random. There is no selective advantage for any genotype and hence no selection. There is no mutation, migration or genetic drift.
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What is Speciation?
Splitting of a gentically similar population into two or more populations taht undergo genetic differentiation and eventually reproductive isolation, leading to evolution of two or more new species
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What is Allopatric speciation?
Formation of two different species from one original species due to geographical isolation (e.g. bodies of water or mountains)
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What is sympatric speciation?
Formation of two different species from one original species, due to reproductive isolation, while the populations inhabit same geographical location?
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In what way can populations be reproductivally isolated?
Genetic changes: prevent gamete fusion, make zygote unable to develop or lead to infertile offspring. Or changes in courtship behaviour (mating seasons) or genitalia structure
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Card 2

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What is a phenotype?

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Visible characteristics of an organism

Card 3

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What is a mutagen?

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Card 4

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What types of chromosomal mutations are there?

Back

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Card 5

Front

What stages of Meiosis result in genetic variation?

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