Inheritance Flashcards

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1
Q

How genotype is linked to phenotype

A

basic:
- genotype refers to the
genetic makeup,
commonly used in ref to the
paired alleles carried by an organism
- that give rise to a phenotype, which is
a physical manifestation of a genetic trait

explanation:
- phenotype depends on the different combination of alleles at each gene locus
- may depend on
interactions between 2 or more genes
- a range of phenotypes may also be controlled by the
combined effect of multiple genes

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2
Q

dominant inheritance
(interaction between alleles at one gene locus)

A
  • when genotype consists of either 1 or 2 copies of the dominant allele of a gene
  • organism displays the dominant phenotype, as a result of
    the presence of a protein
  • as effect of recessive allele is masked by that of dominant allele in a heterozygote
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3
Q

recessive inheritance (interaction between alleles at one gene locus)

A
  • when genotype consists of 2 copies of recessive allele of gene
  • organism displays the recessive phenotype, as a result of
    the lack of protein
    (- which could result in lethality if protein is critical to embryonic development )
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4
Q

incomplete dominance (interaction between alleles at one gene locus)

A
  • when genotype has 2 incompletely dominant alleles
  • organism displays an intermediate phenotype
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5
Q

co-dominance (interaction between alleles at one gene locus)

A
  • when genotype has 2 co-dominant alleles,
  • organism simultaneously expresses the phenotypes of both types of homozygotes
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6
Q

epistatic gene interaction (interaction between 2 or more genes)

A

allele(s) of epistatic gene mask the effect of alleles of hypostatic gene

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7
Q

combined effect of multiple genes / polygenes

A
  • genes act of phenotype in an additive manner
  • and effects of single genes are too slight to be detected
  • effect: leads to continuous variation of trait in phenotype
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8
Q

effect of temp on coat /fur colour in Himalayan rabbits

A
  • Himalayan rabbits are homozygous for Ch allele of tyrosinase gene
  • which codes for a heat-sensitive form of enzyme tyrosinase
  • which is needed for melanin production resulting in black fur
  • however, heat-sensitive tyrosinase is active only when air temp is below 33 ºC
  • thus black fur only grow in parts of the body that are cool enough (e.g. extremities)
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9
Q

Effect of diet on differentiation in honey bees

A
  • queen bees and workers bees have the same mount of genetic material
  • but are phenotypically different;
  • in which workers are infertile while queen is fertile
  • due to difference in diet of bee larvae;
  • in which larvae destined to be workers are switched to a diet containing honey and pollen
  • while those destined to be the queen is fed with royal jelly
  • high content of protein in royal jelly stimulate formation and maturation of the female repro system
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10
Q

how chi-squared test results can support a sample being an example of (autosomal) linkage

A
  • X^calc > X^crit
  • probability that chance alone is reason for difference between observed and expected results is less than 5%
  • observed results do not fit expected 9:3:3:1 phenotypic ratio (i.e. Mendelian inheritance)
  • with there being a larger no of parental phenotypes than recombinant phenotypes
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11
Q

explaining the mode of inheritance

A
  • autosomal or sex-linked
    • sex-linked: father with disease would produced daughters that all have the disease
    • autosomal: prove that it is not sex-linked
  • recessive or dominant
    • recessive: both parents which have the disease should have children which all have the disease
    • dominant:
      • prove that it is not recessive
      • no skipping of generations

use specific context for evidence
e.g. if given pedigree,
II-6 who has red hair has a daughter, III-5 who does not have red hair

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