Single genes and disorders Flashcards

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1
Q

Define:
Allele
Genotype
Phenotype

A

Allele: one of two or more alternative forms of a gene

Genotype: genetic constitution of an organism

Phenotype: Observable properties of an organism produced by a combination of genotype and environment

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2
Q

What is a mutation?

Nonsense? Missense? Synonymous? Point?

A

Alteration in DNA or chromosome sequence or structure. The sources of alleles and genetic variation.

Nonsense - change in sequence coding for a stop codon
Missense - change to amino acid sequence of protein
Synonymous - base substitution but no change to amino acid
Point - single base substitution

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3
Q

What can an insertion or deletion lead to?

A

Can lead to a frameshift mutation which throws off all the codons for the amino acids.

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4
Q

How can a mutation in an intron have an effect?

A

A gene being transcribed has regulatory points where proteins bind and if these change, the proteins will not bind and this affects transcription.

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5
Q

What is a homozygote?

A heterozygote?

A

Homozygote = a diploid organism having the same alleles at one or more genes

Heterozygote = a diploid organism having different alleles at one or more genes

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6
Q

What is a haploinsufficent gene?

A

The heterozygote makes 50% of normal level gene product but this is not enough for normal function.

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7
Q

What are the two types of autosomal inheritance?

A

Dominant and recessive

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8
Q

Give some rules on inheritance patterns in autosomal dominant inheritance

A
  • Males and females affected equally

- Probability of an affected child is 50% is one parent is homozygous recessive and the other is heterozygous dominant

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9
Q

Give some rules on Sex (X) linked recessive inheritance

A
  • More frequent in males as they have only one X chromosome
  • Cannot be passed from father to son as Y chromosome comes from father
  • All daughters of affected fathers are carriers
  • By probability, half the sons of a carrier will be affected and half their daughters will be carriers.
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10
Q

Give a point on multifactorial inheritance

A

Most common traits are multifactorial: arising from the action of two or more genes and interaction between genes and the environment.

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