Gene Muations

Question 1

What is a mutation?

Answer 1

Change in the nucleotide sequence that can be passed on from one cell or organism to another

Question 2

What is a somatic mutation?

Answer 2

Occur in body cells, passed to daughter cells in mitosis but not to offspring

Question 3

What is a germ line mutation?

Answer 3

Occur in cells that give rise to gametes, passed to offspring at fertilization

Question 4

What is a loss of function mutation?

Answer 4

Gene is not expressed at all, or protein does not function. Nearly always recessive

Question 5

What is a gain of function mutation?

Answer 5

Produced a protein with an altered function. Usually dominant

Question 6

What is a conditional mutation?

Answer 6

Phenotype altered only under certain conditions

Question 7

What is a reversion mutation?

Answer 7

Gene is mutated a second time and DNA reverts back to the original sequence or to a different sequence that results in a non mutant phenotype

Question 8

What is a point mutation?

Answer 8

Insertion or deletion of a single base pairs, or substitution of one base pair for another

Question 9

What are the two types of substitutions?

Answer 9

Transition

Transversion

Question 10

What is a silent mutation?

Answer 10

Substitution that results in a codon that codes for the same amino acid

Question 11

What is a missense mutation?

Answer 11

Substitution resulting for a different amino acid

Question 12

What is a nonsense mutation?

Answer 12

Base substitution results in a stop codon somewhere in the mRNA

Question 13

What is a loss of stop mutation?

Answer 13

Base pair substitutions that changes a stop codon for a sense codon. Extra amino acids are added to the polypeptide

Question 14

What is a frame shift mutation?

Answer 14

Insertion or deletion of base pair. Produces non functional proteins

Question 15

How can chromosomal rearrangements cause extensive changes in DNA?

Answer 15

DNA molecules can break and rejoin, disrupting genetic sequences

Can be caused by damage to chromosomes by mutagens or by errors in chromosome replication

Question 16

How can duplication cause changes to DNA?

Answer 16

Homologous chromosomes break at different positions and reconnect to the wrong partners. Can also be caused by inappropriate alignment of homologous during prophase 1 followed by crossing over

Question 17

What is translocation?

Answer 17

Segment of DNA breaks off and attaches to another chromosome, can cause duplications and deletions

Question 18

What is a retrovirus?

Answer 18

Insert their DNA into the host genome at random

If insertion is within a gene, it can cause a loss of function mutation

Viral DNA can remain in the host genome and be passed from one generation to the next. This is called an endogenous retrovirus.

Question 19

What are transposons?

Answer 19

Insert themselves into genes and cause mutations

Can move from one position in genome to another, and usually carry genes to encode enzymes for this movement

Short sequences can be left behind and become mutations

Some transposons replicate and copies are inserted into new sites

Some genomic DNA is sometimes carried along with the transposon, resulting in gene duplication

Question 20

What is a spontaneous mutation and what causes them?

Answer 20

Occur with no outside influence

Causes:
Mistakes during replication
Chemical reactions can alter bases
Meiotic errors

Question 21

What is an induced mutation and what causes it?

Answer 21

Agent from outside cell (a mutagen) causes a change in DNA

Causes:
Mutagens can alter bases
Some chemicals add other groups or bases

Question 22

How can radiation induce mutations?

Answer 22

Ionising radiation creates highly reactive free radicals, which can change bases into forms not recognised by DNA polymerase

Ionising radiation can also break the sugar-phosphate bonds of DNA, causing chromosomal abnormalities

UV radiation is absorbed by thymine, causing it to form covalent bonds with adjacent bases and disrupt DNA replication

Question 23

How can mutations be beneficial?

Answer 23

Provide genetic diversity for natural selection

Question 24

What is an example of a deleterious mutation?

Answer 24

Sickle cell disease

Mutations in the HBB gene cause sickle cell disease

HBB gene provided introductions for making one part of haemoglobin (beta-globin)

Mutations in HBB gene lead to abnormal versions of beta globin

HBB mutations can also result in unusually low levels of beta globin. This abnormality is called beta thalassemia

Question 25

How can we detect and analyse mutations?

Answer 25

Using restriction enzymes: Bacteriophages inject their DNA into the host bacteria cell, causing a cell to produce more virus particles Bacterial defenses include restriction enzymes that cut DNA into smaller, non infectious fragments Restriction enzymes break bonds between the 3' OH of one nucleotide and the 5' phosphate group of the next Bacterial restriction enzymes can be isolated and used to identify DNA sequences of other organisms If DNA from any organism is incubated in a test tube with a restriction enzyme, that DNA will be cut wherever the restriction site occurs DNA fragments are separated to identify where the cubs were made- gel electrophoresis

Question 26

What 3 types of information does gel electrophoresis give?

Answer 26

Number of fragments Size of fragments Relative abundance of fragments, indicated by intensity of band

Question 27

What is a single nucleotide polymorphisms?

Answer 27

Inherited variations of a single base

Question 28

What is a shirt tandem repeat (STRs)?

Answer 28

Short repetitive sequences, usually in non coding regions, that are inherited