Ch 4

Question 1

What are mutations

Answer 1

Changes to dna
- spontaneous
- mutagens

Question 2

What is a mutagen

Answer 2

Chemical/physical substances or events causing mutation
In somatic cells only the daughter cells are effected
In germ cells gamete cells are effected and can pass mutations onto offspring

Question 3

Spontaneous mutations

Answer 3

DNA is exposed for replication during S phase and nitrogen bases are effect.
If not detected in G2 phase damaged DNA is duplicate into new cells.
For example adenosine undergoes chemical change to resemble Guanine which codes for the wrong base pair.

Question 4

Physical mutagens

Answer 4

Uv light - cross-linking neighbouring nucleotides changing DNA structure
X-rays - gene and chromosome abrasions
Nuclear radiation - Breaks DNA into strands

Question 5

chemical mutagens

Answer 5

Mustard gas - effects guanine causing substitution mutation
nitric acid - adenine in DNA is deaminated to behave line guanine

Question 6

substitution mutation

Answer 6

when a DNA base is replaced by another

Question 7

frame shift mutation

Answer 7

when a base is added or subtracted which changes all the codons after the mutation

Question 8

non-sense mutation

Answer 8

substitution mutation - any genetic mutation causing the coding of a stop codon

Question 9

missense mutation

Answer 9

substitution mutation - any genetic mutation that changing the resulting amino acid from one to another

Question 10

silent mutations

Answer 10

substitution mutation - missense mutation
Codon codes for the same amino acid therefore doesnt effect protein produced
eg CCC and CCT both code for Gly

Question 11

conservative mutations

Answer 11

missense mutation
mutations which change the amino acid coded to a similar type of amino acid eg both acidic or both polar

Question 12

non-conservative mutations

Answer 12

missense mutation
the new amino acid is not of the same type

Question 13

where do genetic mutations occur

Answer 13

mutations originate at the DNA level but appear at the protein level

Question 14

insertion mutation

Answer 14

frame shift mutation - one or more nucleotide pairs have been added to a segment of DNA

Question 15

deletion mutation

Answer 15

frame shift mutation - one or more nucelotide pairs are removed

Question 16

point mutation

Answer 16

When a single base pair is altered through substitution, deletion or addition (frameshift)
effected sequences are called SNP’s or snips (single nucleotide polymorphisms)

Question 17

nitric acid

Answer 17

adenine is deaminated so it acts line guanine

Question 18

mustard gas

Answer 18

affects the base guanine causing a substitution mutation

Question 19

biological agents

Answer 19

when invasive pathogens like bacteria or viruses causes a mutation by imbedding its DNA into the host cells causing mutations in the daughter cells.

Question 20

what are the mechanisms of variation

Answer 20

Mutation
Sexual reproduction
Environmental factors

The diversity of genetic and phenotypic traits within and between populations

Question 21

Neutral mutations

Answer 21

Protein produced is unaffected by the change, posing no threat to the organism

Question 22

Deleterious mutations

Answer 22

Disruption in the function of a protein affecting the organisms ability to carry out vital processes

Question 23

Beneficial mutation

Answer 23

When changes in the synthesis of a protein benefits the organisms survival rates eg HIV resistance due to the absence of a surface protein required for the virus to enter

Question 24

what causes mutations

Answer 24

errors in DNA replication or cell division OR damage by chemical or physical environmental factors.

Question 25

what types of cells can mutations affect?

Answer 25

somatic/body via mitosis
germ/sex cells via meiosis (passed onto offspring)

Question 26

conditional mutation

Answer 26

substitution mutation - environmentally dependent

Question 27

monoploidy

Answer 27

organisms with a single set of chromosomes
eg male ants bees wasps
in humans causes turners syndrome

Question 28

polyploidy

Answer 28

organisms have one or more complete sets of chromosomes
eg ferns, flowering plants, algae

Question 29

aneuploidy

Answer 29

having an abnormal amount of chromosomes
eng a human having 45 or 47 instead of 46.
occurs due to a non-disjunction where chromosomes don’t segregate during meiosis and half the gametes will have a chromosome pair and the other half will have none

Question 30

how do new alleles form

Answer 30

mutations

Question 31

what do alleles introduce

Answer 31

genetic variation

Question 32

where do most mutations occur

Answer 32

somatic cells - aren’t inherited

Question 33

how do you describe the fitness of a mutation

Answer 33

its value to the survival and reproductive success of an organism
described as - lethal, harmful, silent/neutral or beneficial/useful

Question 34

what are the sources of variation

Answer 34

1- mutations
2 - genetic recombination during meiosis (crossing over, independent assortment and random mating)

Question 35

what’s crossing over

Answer 35

homologous chromosomes exchange sections of DNA

Question 36

what’s independent assortment

Answer 36

how different genes separate when reproductive cells develop
during metaphase 1 of meisosis

Question 37

what’s random mating

Answer 37

random fusion of gametes leads to variation of offspring (random sperm have equal opportunity to fuse with 1 egg)

Question 38

what are the types of chromosomal rearrangements during crossing over

Answer 38

deletions (chromosome breaks at 2 spots removing a gene)
inversions (chromosome breaks in 2 places & inverts 180o)
translocations (a section breaks off and re-attaches to another chromosome)
duplications (an extra copy of a section of a chromosomes made)

Question 39

what happens when a chromosomes broken or rearranged during meiosis

Answer 39

variation occurs