Mutations

Question 1

Define mutation

Answer 1

A change in genetic information (DNA )

Question 2

T or F: mutations are responsible for the huge diversity of genes and are a source of new genes

Answer 2

True

Question 3

What are the two scales of mutations?

Answer 3

Large scale

Small scale

Question 4

What is a genetic disorder or hereditary disease?

Answer 4

when a mutation has an adverse effect on the phenotype

Question 5

Define forward mutation

Answer 5

A change from the wild type allele to a different allele

Question 6

Define wild type

Answer 6

The phenotype most commonly observed in natural populations

Question 7

Define reverse (reversion) mutation

Answer 7

A change from the mutant allele to the wild type allele

Question 8

Define germ-line mutation

Answer 8

Mutation that can affect future generations because they occur in the gametes

Question 9

Define somatic mutation

Answer 9

Mutation that only affects individuals, often causes cancer

Question 10

What are two causes of mutations?

Answer 10

1. induced
   - caused by mutagens
2. Spontaneous:
   - errors during replication

Question 11

Define mutagens and provide examples

Answer 11

physical and chemical agents that interact with DNA and cause mutations

ex. UV and X rays (physical)

or nucleotide analogs that are chemically similar to DNA nucleotides but pair incorrectly (chemical)

Question 12

Define small-scale mutations and list the 3 types

Answer 12

Change in one or a few nucleotide pairs

1. silent mutations
2. missense mutations
3. nonsense mutations

Question 13

Define silent mutations and phenotypic results

Answer 13

Small-scale mutations that occur from a change in a nucleotide pair that does not change which amino acid the codon is translated to

No observable effect on phenotype because the same amino acid is coded for

Question 14

Which letter in the codon triplet would have the least effect if changed?

Answer 14

The third one

Question 15

Define missense mutations and phenotypic results

Answer 15

Small scale mutation that changes one amino acid to another

May have a little effect on the protein if:

• the amino acids have similar properties
• if the amino acid is in a region of the protein where the function of the protein wouldn’t be affected

or it can have a phenotypic effect if not.

Question 16

Define nonsense mutations and phenotypic results

Answer 16

Small scale mutation where the codon is changed from coding for an amino acid into a stop codon

causes translation to be terminated before the polypeptide is complete

Usually leads to nonfunctional proteins

Question 17

Define point mutations and list the two main types

Answer 17

Changes in a single nucleotide pair, occurs in small scale mutations

1. substitution
2. indel

Question 18

When will a point mutation be inherited by offspring? What is an example of this?

Answer 18

If it occurs in a gamete or pre-gametic cell

ex. familial cardiomyopathy

Question 19

Define substitution mutations and describe the mutation result that can occur

Answer 19

A point mutation that replaces one base pair with another

usually causes missense mutations

some can be silent due to the redundancy of genetic code

some can be nonsense

Question 20

What is an example of a substitution missense mutation?

Answer 20

Sickle-cell anemia

Results in an abnormal beta-globin polypeptide

Question 21

Define indel mutations and list the two kinds

Answer 21

A point mutation that is caused by the insertion or deletion of one or more nucleotide pairs

1. insertion: addition of a nucleotide pair in a gene
2. deletion: loss of a nucleotide pair in a gene

Question 22

What are the consequences of indel mutations?

Answer 22

Usually severe because they can cause a frameshift mutation

Can cause extensive missense that usually ends in nonsense

Question 23

Define frameshift mutation

Answer 23

Changes to the reading frame in which the nucleotide triplets are read in different groups (and therefore code for different amino acids)

caused by indel point mutations

Question 24

Define large scale mutations

Answer 24

Abnormal chromosome number or alterations of chromosome structure

Question 25

Define genome mutations

Answer 25

Changes in chromosome number, either polyploidy or aneuploidy

Question 26

Define euploidy

Answer 26

A genome mutation

an exact multiple of the haploid number of chromosomes

Question 27

Define polyploidy

Answer 27

A genome mutation with more than two complete sets of chromosomes

Question 28

Which type of large scale mutation is common in plants?

Answer 28

Polyploidy

Question 29

Define monoploidy

Answer 29

A genome mutation that results in lethal alleles being expressed

Question 30

Which animal species are monoploidy?

Answer 30

male bees, wasps and ants that develop from unfertilized eggs

Question 31

Define triploid

Answer 31

3 complete sets of chromosomes

usually sterile

ex. watermelon and bananas

Question 32

Define aneuploidy

Answer 32

Having an abnormal number of a particular chromosome

ex. 2n-1 or 2n+1 for a diploid organism

Question 33

T or F: most human aneuploid embryos survive until birth

Answer 33

FALSE. mostly spontaneously abort

Question 34

What can cause aneuploidy?

Answer 34

nondisjunction

Question 35

Define nondisjunction

Answer 35

Failure of homologous chromosomes to separate during meiosis I

or

Failure of sister chromatids to separate during meiosis II

This can also happen to sister chromatids in mitosis

Question 36

What are two aneuploidy results of nondisjunction?

Answer 36

Monosomy and trisomy

Question 37

Describe monosomy. Which syndrome survives to birth?

Answer 37

An aneuploidy result of nondisjunction that results in only one chromosome of a pair (2n-1)

Turner Syndrome (XO)
- only in females, short, usually infertile

Question 38

Describe trisomy. Which syndromes survive to birth?

Answer 38

An aneuploidy result of nondisjunction which results in an extra copy of a chromosome (2n+1)

XXY (Klinefelter syndrome)
XYY syndrome
XXX

Question 39

What is the only autosomal trisomy that can be survived into adulthood?

Answer 39

Trisomy 21 (Down’s Syndrome)

Question 40

What causes chromosome mutation?

Answer 40

Errors in meiosis (chromosome breakage, improper crossing over) or damage from things like radiation

Question 41

Why does chromosome mutation cause problems?

Answer 41

Because of an imbalance of genetic material or damage to genes at break sites

Question 42

What are the four types of changes that can occur in chromosome structure?

Answer 42

Deletion
Duplication
Inversion
Translocation

Question 43

Define deletion

Answer 43

A type of alteration to chromosome structure

Occurs when a chromosomal fragment is lost and the chromosome is then missing some genes

Question 44

What are the consequences of deletion in chromosome structures?

Answer 44

On X chromosome of male, it is usually lethal

Cri du Chat (chromosome 5) has severe effects

Question 45

Define duplication

Answer 45

A type of alteration to chromosome structure

A deleted fragment can become attached to a sister chromatid

Question 46

What are the consequences of duplication in chromosome structures?

Answer 46

ex. duplication of potentially cancer causing genes can cause cancer

Question 47

Define inversion

Answer 47

A type of alteration to chromosome structure

When a deleted fragment reattaches to the original chromosome but in the reverse orientation

Question 48

What are the consequences of inversion in chromosome structures?

Answer 48

Most human inversion occurs on chromosome 9 and can impact fertility

Question 49

Define translocation

Answer 49

A type of alteration to chromosome structure

When a deleted fragment joins a non-homologous chromosomes

Question 50

What are the consequences of translocation in chromosome structures?

Answer 50

ex. if SRY gene from Y chromosome is moved to an X chromosome, it results in XX male syndrome