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Biology IB HL - 10.2 Inheritance Part 2

Biology30 CardsCreated about 1 month ago

This deck covers key concepts related to inheritance, focusing on recombinant phenotypes, linked genes, polygenic traits, and the influence of environmental factors on phenotypic variation.

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Why will non-recombinant phenotypes be more rare?

This is because crossing over is a random process and chiasmata do not form at the same locations with every meiotic division
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Key Terms

Term
Definition
Why will non-recombinant phenotypes be more rare?
This is because crossing over is a random process and chiasmata do not form at the same locations with every meiotic division
What will the relative frequency of recombinant phenotypes be dependent on?
The relative frequency of recombinant phenotypes will be dependent on the distance between linked genes
When will recombination frequency be greater?
Recombination frequency between two linked genes will be greater when the genes are further apart on the chromosome
Why is recombination frequency greater when genes are further apart?
This is because there are more possible locations where a chiasma could form between the genes
How can recombinant phenotypes be identified?
Recombinant phenotypes can be identified by performing a test cross (crossing with a homozygous recessive for both traits)
How is it possible to determine whether genes are liked or unlinked?
It is possible to infer whether two genes are linked or unlinked by looking at the frequency distribution of potential phenotypes
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Biology IB HL - 10.2 Inheritance Part 2
TermDefinition
Why will non-recombinant phenotypes be more rare?
This is because crossing over is a random process and chiasmata do not form at the same locations with every meiotic division
What will the relative frequency of recombinant phenotypes be dependent on?
The relative frequency of recombinant phenotypes will be dependent on the distance between linked genes
When will recombination frequency be greater?
Recombination frequency between two linked genes will be greater when the genes are further apart on the chromosome
Why is recombination frequency greater when genes are further apart?
This is because there are more possible locations where a chiasma could form between the genes
How can recombinant phenotypes be identified?
Recombinant phenotypes can be identified by performing a test cross (crossing with a homozygous recessive for both traits)
How is it possible to determine whether genes are liked or unlinked?
It is possible to infer whether two genes are linked or unlinked by looking at the frequency distribution of potential phenotypes
How is it possible to tell that offspring have unlinked genes?
Offspring with unlinked genes have an equal possibility of inheriting any potential phenotypic combination
Why do offspring with unlinked genes have an equal possibility?
This is due to the random segregation of alleles via independent assortment
How is it possible to tell that offspring have linked genes? (there is one exception)
Offspring with linked genes will only express the phenotypic combinations present in either parent unless crossing over occurs
Which phenotype appears less often in offspring with linked genes?
Consequently, the ‘unlinked’ recombinant phenotypes occur less frequently than the ‘linked’ parental phenotypes
What are chi-squared tests used for?
Chi-squared tests are a statistical measure that are used to determine whether the difference between an observed and expected frequency distribution is statistically significant
What does it suggest if observed frequencies do not conform to those expected for an unlinked dihybrid cross?
Genes are linked and hence not independently assorted
How may phenotypes vary? (2 ways?
Variation in phenotypes for a particular characteristic can be either discrete (discontinuous) or continuous
What are monogenic traits?
Monogenic traits (characteristics controlled by a single gene loci) tend to exhibit discrete variation, with individuals expressing one of a number of distinct phenotypes
What are polygenic traits?
Polygenic traits (characteristics controlled by more than two gene loci) tend to exhibit continuous variation, with an individual’s phenotype existing somewhere along a continuous spectrum of potential phenotypes
For polygenic inheritance, what does increasing the number of loci do?
Increasing the number of loci responsible for a particular trait increases the number of possible phenotypes
What curve does the phenotypic distribution show for polygenic traits?
This results in a phenotypic distribution that follows a Gaussian (bell-shaped) normal distribution curve
What is an example of a polygenic trait?
An example of a polygenic trait is grain colour in maize (wheat), which is controlled by three gene loci
How may grain colour vary and why?
Grain colour can range from white to dark red, depending on the amount of pigment that is expressed
What does each gene have in maize?
Each gene has two alleles, which either code for red pigment or white pigment
What do the most frequent combinations have in terms of alleles for maize?
The most frequent combinations have an equal number of the two allele types
What is rare in maize?
Conversely, combinations of one extreme or the other are relatively rare
What pattern does polygenic genes in maize show?
The overall pattern of inheritance shows continuous variation
What can phenotypic variations also be determined by, apart from the genotype?
Phenotypic characteristics are not solely determined by genotype, but are also influenced by environmental factors
What is the role of environmental factors in determining phenotype?
The added effect of environmental pressures functions to increase the variation seen for a particular trait
What is an example of a polygenic trait affected by environmental factors?
One example of a polygenic trait that is influenced by environmental factors is human height
What is human height controlled by?
Human height is controlled by multiple genes (polygenic), resulting in a bell-shaped spectrum of potential phenotypes
Apart from the genotype, what environmental factors can affect human height?
Environmental factors such as diet and health (disease) can further influence an individual human’s height
Apart from height, what other trait is polygenic and affected by environmental factors?
human skin colour
What is human skin colour controlled by?
Skin colour is controlled by multiple melanin producing genes, but is also affected by factors such as sun exposure