Inheritance Flashcards

1
Q

What is genetics?

A

Study of inheritance and variation.

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2
Q

What are the sources of variation in genetics?

A
  1. Mutation

2. Meiosis - cross-over and random assortment

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3
Q

What are genotype and phenotype?

A
  • Genotype = set of genes responsible for a particular trait (DNA).
  • Phenotype = physical expression of a particular trait (protein).
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4
Q

What do the terms homozygous, heterozygous and hemizygous mean?

A
  • Homozygous = 2 alleles of a gene are the same
  • Heterozygous = 2 alleles of a gene are different
  • Hemizygous = only 1 allele of a gene on the X chromosome, i.e. Males only
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5
Q

What do the terms dominant and recessive mean?

A
  • Dominant = allele determining the phenotype in a heterozygote
  • Recessive = non-dominant allele in a heterozygote
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6
Q

What is co-dominance?

A

2 alleles are expressed equally, creating a new phenotype.

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7
Q

Give an example of a gene that can show co-dominance of alleles.

A
  • Human isoglutamin gene codes for glycoproteins on RBC surface - determines ABO blood types.
  • Gene I has 3 alleles: A, B and O:
    • allele A is dominant over allele O
    • allele B is dominant over allele O
    • alleles A and B are co-dominant
  • 4 possible genotypes: blood group A, B, AB and O.
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8
Q

What is polygenic inheritance?

A

More than 1 gene involved in producing a phenotype (e.g. Multiple genes coding for multiple enzymes required for a single product).

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9
Q

Give an example of a polygenic trait that may result in disease.

A

Albinism is inherited in a recessive manner but is polygenic - even if 2 parents are inherited, offspring may not be is parents are affected in different genes.

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10
Q

What is genome complementation?

A

2 genomes complement each other if heterozygous for each allele.

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11
Q

What is the difference between linked and unlinked genes?

A
  • Linked: genes are on the same chromosomes - do not show independent assortment at meiosis
  • Unlinked: genes are on different chromosomes
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12
Q

What does recombination frequency between 2 linked genes depend on?

A

The distance between genes:

  • genes close together are tightly linked.
  • genes that are apart on the same chromosome almost behave as unlinked genes due to crossing over.
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13
Q

What is the ration of linked and unlinked genes in gametes?

A
  • Unlinked genes: 1:1:1:1
  • Linked genes not 1:1:1:1 as rate dependent on how often cross-over occurs, itself dependent on distance between genes on chromosomes.
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