Lecture 1 - Mutations and Disease Flashcards

1
Q

Locus

A

Position on a chromosome where a particular gene or genetic marker is located

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2
Q

Gene

A

A section of DNA that codes for a molecule that has a function

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3
Q

Allele

A

A variant form of a locus or gene

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4
Q

Genotype

A

The genetic constitution of an individual at a locus or multiple loci

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5
Q

Phenotype

A

Observable trait or set of traits of an individual. May be a consequence of genetics, the environment, or both.

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6
Q

Mutations

A

Changes in the genetic sequence

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7
Q

Substitution mutation

A

Replace one nucleotide with another

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8
Q

SNP

A

Single nucleotide polymorphyism

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9
Q

Synonymous mutation

A

Nucleotide change in a codon that does not alter the amino acid (aka. silent mutation)

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10
Q

Non-synonymous mutation

A

Nucleotide change in a codon that alters the amino acid

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11
Q

Types of non-synonymous mutations

A

Missense and nonsense

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12
Q

Missense mutation

A

Nucleotide change in a codon that alters the amino acid

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13
Q

Nonsense mutation

A

Nucleotide change that causes substitution for a stop codon, results in a shorter protein due to protein synthesis stopping early

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14
Q

Insertion mutation

A

Addition of one or more nucleotides

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15
Q

Deletion mutation

A

Removal of one or more nucleotides

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16
Q

Frameshift mutation

A

Changes the reading frame, deletion or insertion mutation

17
Q

Slippage

A
  • Mechanism for frameshift mutations
  • New strand or template strand loops out causing an insertion or deletion of a nucleotide

Template strand loops = deletion

New strand loops = insertion

18
Q

Citrullinaemia in cattle

A
  • Inborn error of metabolism leads to ammonia poisoning
  • Recessive condition
  • Calf dies 3-5 days after birth
  • Loss of the enzyme argininosuccinate synthetase means urea cycle cannot be completed, causes buildup of upstream molecules (ammonia)
19
Q

Mendelian disorders

A

Occur when specific mutations in single genes are inherited from either of one’s two parents

20
Q

What mutation causes citrullinaemia

A

A single base substitution at codon 86 where a C becomes T, creates a stop codon

21
Q

Recessive alleles

A

The phenotype is observed only in individuals homozygous for the allele (need both copies of the recessive allele to present the trait)

22
Q

Dominant allele

A

The phenotype is observed in individuals homozygous for the allele and in heterozygotes (only need one or more copies of the allele)

23
Q

Semi-dominant/incomplete allele

A

The heterozygote exhibits a phenotype intermediate to the two homozygote phenotypes

24
Q

Co-dominant allele

A

Heterozygote exhibits the phenotypes of both homozygotes

25
Extension gene in horses
- Dominant allele - Horses with dominant allele copy will be black (EE or Ee) - Horses homozygous for the recessive gene (ee) will be chestnut
26
Dilution gene in horses
- Incomplete dominance - Causes dilution of base color - N/N : black base - N/Cr : smoky black - Cr/Cr : smoky cream - N/N : chestnut - N/Cr : palomino - Cr/Cr : cremello
27
It is easy to eliminate a (dominant/recessive) allele from a population
Dominant, all carriers of the allele express the phenotype
28
Why is it difficult to eliminate a recessive allele from a population?
Heterozygous individuals do not express the unwanted phenotype, helpful to use genetic markers in this case
29
Gene that causes myostatin deficiency
GDF8 - growth differentiation factor 8 This gene normally inhibits muscle growth
30
Myostatin deficiency phenotype
Increased muscle mass
31
Downside of myostatin deficiency
- Neonatal calves are large, more c-sections required - Require more nutrient dense feed - More susceptible to a number of conditions including heat stress and dystocia
32
Is myostatin deficiency dominant or recessive?
Recessive
33
Can only one gene cause double muscling?
No, there are different mutations that can lead to the same phenotype
34
Ehlers-Danlos syndrome
Stretchy and fragile skin due to abnormal collagen Can be caused by any of the 4 genes involved in collagen production