Mutations Flashcards

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1
Q

Mutation

A

Changes in the DNA that replace, insert, or delete nucleotides

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2
Q

Mutations are the ultimate source of…

A

All new genes and the genetic diversity of life

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3
Q

2 main categories of mutations

A

1) Large Scale
2) Small Scale

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4
Q

Large Scale Mutations

A

Affect long segments of DNA

(chromosomal rearrangement)

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5
Q

Small Scale Mutations

A

Affect one or a few nucleotide pairs

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6
Q

Mutations can alter phenotypes by…

A

Impacting gene product sequence or expression

–> Altering levels of mRNA + proteins or the STRUCTURE of these molecules

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7
Q

Mutations in Non-Coding Regions of DNA

A

Don’t impact structure/function of gene products but instead alter gene expression and regulation

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8
Q

Most mutations are within the…

A

Non-coding region of DNA

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9
Q

Germ Cell Mutations

A

Inherited between generations

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10
Q

Somatic Cell Mutations

A

Not inherited

–> But can cause serious problems for people when cells with a mutation proliferate (= cancer)

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11
Q

What factors determine phenotypic effect of a mutation?

A

1) The type of cell
2) When in the life cycle the mutation occurs (the earlier the more severe its effects)
3) The dominance of a mutation

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12
Q

Point mutations

A

Changes in a single nucleotide pair of a gene (single base pair change)

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13
Q

2 main types of point mutations:

A

1) Substitutions
2) Deletions/Insertions

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14
Q

Substitution Mutations

A

The replacement of one nucleotide and its partner with another pair of nucleotides

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15
Q

Types of substitution mutations

A

1) Missense
2) Nonsense
3) Silent

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16
Q

Missense Mutations

A

Change of ONE codon for another which results in a change in the amino acid

–> Causes change in a SINGLE POINT!!!

SUBSTITUTIONS

17
Q

Mutation in Sickle Cell Anemia

A

Missense mutation (in hemoglobin)

(A shift from an “a” to a “t”)

Wild type cells = Produce glutamic acid (- charge) at that position

Mutated cells = Produce VALINE (neutral charge) at that position

–> **Replacement of glutamic acid with valine

18
Q

In sickle cell anemia, what leads to the formation of sickled cells?

A

The change in the charge of hemoglobin thanks to the replacement (substitution) of glutamic acid (+) by valine (neutral) affects its STRUCTURE

–> Hb forms needle like aggregates within RBCs, giving them their sickled shape

19
Q

Nonsense Mutation

A

PREMATURE STOP CODON –> Termination of polypeptide happens earlier than it should

20
Q

How does a nonsense mutation impact the final polypeptide product?

A

It shortens it

–> the resulting polypeptide will be shorter and incomplete

21
Q

Severity of the effect of a nonsense mutation is dependent upon:

A

Where(“/when”) in the sequence the mutation occurs

–> At the end = almost entire protein is produced normally (less severe)

–> At the beginning = almost no protein is produced (more severe)

22
Q

Silent Mutations

A

Substitutions that have no effect on amino acid sequence!

23
Q

Why are silent mutations possible?

A

Redundancy of the genetic code (multiple codons call for the same amino acid)

24
Q

Although silent mutations don’t have protein sequence, they can still have an effect on phenotype if…

A

The codon change alters “translation efficiency”

–> Most organisms have “codon bias” and are used to dealing with specific codons for amino acids

–> Can affect rate of translation if the new codon is not “preferred” by the cell

25
Q

Insertions/Deletions

A

Additions or deletions of nucleotide pairs in a gene

26
Q

What do insertions and deletions alter?

A

The reading frame

27
Q

Frameshift mutations occur when there is…

A

An insertion or deletion of a number of nucleotides that is NOT divisible by 3

28
Q

What regions of a protein are altered by insertions and deletions that are frame shifting?

A

Protein sequence DOWNSTREAM the insertion or deletion will be different from the original protein

29
Q

Severity of insertions/deletions depends on…

A

Where in the sequence the mutation occurs

–> Closer to beginning = more incorrectly read AAs = greater severity

30
Q

Insertion and deletions cause…

A

Frameshift

31
Q

Insertions and deletions ARE NOT ______________ mutations

but instead are _________________ mutations

A

1) Are NOT nonsense or missense mutations

2) ARE FRAMESHIFT mutations