genetic change - mutation

Question 1

How does mutation introduce new alleles into a population?

Answer 1

radiation or chemical mutagens

mutations is only natural source of all new alleles in a species.

mutation resulting in new allele depends on type - somatic or germline mutation, and whether it occurs in a coding or non-coding region of the DNA

Question 2

mutation

Answer 2

A mutation is any change to the DNA of an organism, that is unpredictable and random.

unpredictable - which gene and how

most have no effect, some result in physical changes

Question 3

types of radiation

Answer 3

Energy transmitted as electromagnetic waves, including light and heat.

Question 4

Ionising radiation

Answer 4

radiation that is strong enough to break the bonds between electrons and the nucleus of an atom creating an ion.

high frequency + high energy

Question 5

direct radiation mutation

Answer 5

where the radiation affects the actual DNA chemistry changing the base sequence.

Question 6

indirect radiation mutation

Answer 6

where the radiation affects other chemicals in the cell which then damage the DNA structure.

Question 7

mutagen

Answer 7

Any chemical or radiation that is capable of causing a mutation.

Question 8

Deaminating agents

Answer 8

Deaminating agents can remove an amino group (containing nitrogen) from a base, turning it into a different base. For example, nitrous acid can convert cytosine into uracil.

Question 9

naturally occurring mutagens

Answer 9

ionising radiation, UV light, fungus, mold

biological or non-biological

some viruses can even cause mutations

Question 10

point mutation

Answer 10

A mutation involving a single nucleotide base.

point mutations which affect genes (sections within a chromosome)

base substitution or frameshift

Question 11

base substitution

Answer 11

A point mutation in which one base is replaced by another.

Question 12

frameshift

Answer 12

where one base is inserted or removed from the DNA chain shifting all other bases along, changing the amino acids that are coded for.

Question 13

silent mutations

Answer 13

these have no effect on the protein produced. The new nucleotide still results in the same amino acid being coded for.

Question 14

missense mutations

Answer 14

these add a different amino acid to the protein that results in the protein being different and may have a deleterious effect. Eg sickle cell anemia.

Question 15

nonsense mutation

Answer 15

the substitution results in the production of the stop codon which ends protein production. Eg Thalassaemia.

Question 16

base deletion

Answer 16

The elimination of a single nucleotide from a DNA sequence.

Question 17

base insertion

Answer 17

The addition of a single nucleotide into a DNA sequence.

Question 18

frameshift mutation

Answer 18

A significant mutation caused by the deletion of a single base, or a number of bases which are not a multiple of 3.

Question 19

Structural chromosomal mutations

Answer 19

section of a chromosome is deleted, duplicated, inverted or translocated to another chromosome.

Question 21

inversion

Answer 21

section of chromosome is inverted (backward)

Question 21

deletion

Answer 21

A block mutation where a section of a chromosome is lost.

Question 22

Chromosomal number mutation

Answer 22

A mutation in which a cell contains (whole) extra or missing chromosomes.

Question 23

aneuploidy

Answer 23

an abnormal chromosome number with either extra or fewer chromosomes than the normal number.

Question 24

polyploidy

Answer 24

when there multiple sets of chromosomes.

Question 25

karyotype

Answer 25

A photograph of the chromosomes in a cell, cut out and arranged into homologous pairs.

Question 26

nondisjunction

Answer 26

The failure of a homologous pair of chromosomes to segregate during meiosis.

Question 27

germline mutation

Answer 27

A mutation that happens in a gamete or a cell that divides to produce gametes. Because germline mutations occur in germ cells, they can be passed to offspring.

Question 28

Somatic mutation

Answer 28

A mutation that happens in a cell that is not a reproductive cell. (body cell) Somatic mutations may have no effect on the individual at all, depending on the gene that is changed.

Question 29

non coding regions

Answer 29

refers to a length of DNA which does not contain the coded instructions for protein synthesis. This is either an intron or flanking region of a gene. Non coding regions of DNA are termed introns.

Question 30

coding regions

Answer 30

Coding regions of DNA are sections that code for a protein. These are also termed exons.

Question 31

fertilisation

Answer 31

Sexual reproduction results in variation of offspring because each individual is a result of the fusion of two gametes carrying different alleles for each gene. This leads to genetic variation. Because each gamete is haploid then the fertilised cell is the result of the combination of each gamete genetic information

Question 32

meiosis and independent assortment

Answer 32

Independent assortment of non homologous chromosomes. non homologous chromosomes contain genes for different conditions. Eg hair colour and skin type. Non homologous chromosomes can assort in a large variety of combinations leading to increased genetic diversity.

Question 33

crossing over during meiosis

Answer 33

Crossing over in meiosis further increases variation among the offspring, because it allows the recombination of alleles which have gene loci on the same chromosome.

Question 34

natrual selection

Answer 34

the most important mechanism of evolution relies on the existence of genetically-based phenotypic variation in the population Since mutation is the source of new alleles, without mutation, there could be no natural selection.

Question 35

genetic drift

Answer 35

There are two ways in which genetic drift can affect the gene pool of a population: the founder effect and a genetic bottleneck.

Question 36

founder effect

Answer 36

hen a new population is formed from a small number of individuals from an existing parent population, but the genetic make up of these ‘founding’ individuals is not representative of the existing population.

Question 37

genetic bottleneck

Answer 37

when a population on the brink of extinction grows in numbers again, but the frequency of alleles is changed because the few individuals that survived give rise to the new population which is not representative of the genetic make up of the original population.

Question 38

gene flow

Answer 38

If a population is not geographically isolated from other populations, then the movement of individuals from other populations into the population is able to (a) introduce new alleles or (b) change the frequency of alleles in the population.