Biology - Review - 9 - whole

Question 1

What are the 4 major types of mutation?

5 types

Answer 1

Point mutation

Substitution mutation

Frame shift mutation

Block or chromosomal mutations

Chromosonal abnormalities

Question 2

What is a Nonsense Substitution mutation?

Answer 2

The new codon is a stop codon and shortens the amino acid chain (which may have severe effects).

Question 3

What is the founder effect?

Answer 3

The founder effect is seen when a small group of individuals breaks away from the main population and colonises a new habitat. The founding individuals will not necessarily represent the allele frequencies seen in the original population. Further changes in allele frequencies in the founding population can arise from new environmental pressures.

Question 4

How does natural variation work in the genes?

Answer 4

Natural variation exists between individuals of the same species because many genes have multiple alleles that are present in the population in different frequencies.

Question 5

What is a nucleotide insertion mutation?

A type of frameshift mutation

Answer 5

A nucleotide insertion adds one or two new nucleotides into the sequence and pushes the rest of the nucleotides back one or two places.

Question 6

What is Genetic Drift?

Answer 6

Genetic drift is the change in allele frequencies in a population due to random events. This is most likely to affect small populations.

Question 7

What are the four basic steps for selective breeding?

Answer 7

There are four basic steps that apply to all forms of selective breeding:

• Determine the desired trait
• Interbreed parents who show the desired trait
• Select the offspring with the best form of the trait and interbreed these offspring.
• Continue this process until the population reliably reproduces the desired trait

Question 8

What are Chromosonal abnormalities and what are the types?

2 types

Answer 8

Chromosomal abnormalities are mutations that involve whole chromosomes, or the number of chromosomes.

The two main forms are:

• Aneuploidy
• Polyploidy

Question 9

Where do new alleles come from?

Answer 9

New alleles, genes and chromosomes are created through mutation.

Question 10

What is Natural selection?

Answer 10

Natural selection is the influence of environmental pressures on allele frequencies of a population, which occurs because of genetic variation between individuals, and the survival and reproduction of those individuals with favourable phenotypes (traits):

• Phenotypes that are better suited to environmental pressures have higher adaptive values than those that are less suited.
• Individuals with alleles associated with the phenotype are more likely to survive and reproduce.
• These alleles are more likely to persist in the gene pool and increase in frequency over time.

Question 11

What is Speciation?

Answer 11

Speciation is the evolution of new species from an ancestral species. The new species are genetically different enough from the ancestral species that they can no longer produce viable offspring should they interbreed.

Question 12

What is a Block Translocation mutation?

Answer 12

Sections from two non- homologous chromosomes are swapped.

Question 13

What is ‘Selective Breeding’?

Answer 13

Selective breeding is the traditional form of artificial selection. In selective breeding, humans select desired traits and interbreed organisms with these traits.

Question 14

What traits are typically bred for in plants?

Answer 14

Agricultural plants are typically bred for high yield and high resistance to common diseases.

Question 15

What is Gene Flow?

Answer 15

Gene flow is the movement of alleles into and out of a gene pool. It can occur when different populations interbreed or individuals migrate between populations.

Question 16

What is a Block Inversion mutation?

Answer 16

A large section of a chromosome is removed and rotated 180° before being reinserted, so that the sequence is reversed.

Question 17

What forms do Substitution mutations take?

Answer 17

A substitution mutation is a point mutation in which one nucleotide is replaced by another type of nucleotide.

• Silent mutations
• Missense mutations
• Nonsense mutations

Question 18

What is a Silent Substitution mutation?

Answer 18

The new codon (triplet) still codes tor the same amino acid.

Question 19

What is a Block Insertion mutation

Answer 19

A whole chromosome or section of a chromosome is added to a different chromosome.

Question 20

What forms do Block mutations take?

Answer 20

Block mutations or chromosomal mutations typically involve multiple genes.

• Duplication mutations
• Deletion mutations
• Inversion mutations
• Insertion mutation
• Translocation mutations

Question 21

What are the 2 mechanisms for evolution?

Answer 21

Evolution can occur through natural selection or artificial selection.

Question 22

What is an Aneuploidy mutation?

Answer 22

Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46.

It does not include a difference of one or more complete sets of chromosomes.

Question 23

What does speciation involve?

Answer 23

Speciation involves either genetic isolation between diverging populations or single species gradually changing over time, with differences in mutations, selective pressures and genetic drift changing allele frequencies and traits in the sub-populations.

Different types of speciation involve different genetic isolating mechanisms.

Question 24

What is a Point Addition mutation?

Answer 24

The mutation introduces a new nucleotide into the sequence, resulting in a frameshift.

Question 25

What recent technologies are used?

Answer 25

More recent molecular technologies have allowed for faster development of genetically modified organisms and for the transfer of DNA between species that cannot interbreed normally.

Question 26

What is a Block Deletion mutation?

Answer 26

Entire genes are cut from the chromosome.

Question 27

What is a Missense Substitution mutation?

Answer 27

The new codon codes for a different amino acid (the effects of which may vary depending on the new amino acid and the resulting functionality).

Question 28

What forms do Frameshift Mutations take?

Answer 28

Frameshift mutations involve one or two nucleotides being either added or removed from a nucleotide sequence, altering every codon in the sequence from that point onwards.

• Nucleotide insertion
• Nucleotide deletion

Question 29

What is a nucleotide deletion mutation?

A type of frameshift mutation

Answer 29

A nucleotide deletion removes one or two nucleotides and pulls all the following nucleotides forwards by one or two places.

Question 30

What is a Block Duplication mutation?

Answer 30

A section of a chromosome is repeated multiple times on that chromosome.

Question 31

What is the Bottleneck effect?

Answer 31

The bottleneck effect is seen when an event often a natural disaster, significantly reduces the size of a population and thus its genetic diversity. It also therefore increases inbreeding, further reducing variation. Genetic drift can remove alleles from the gene pool altogether.

Question 32

What is a Point Deletion mutation?

Answer 32

The mutation removes a nucleotide from the sequence, resulting in a frameshift.

Question 33

Types of Prezygotic isolating mechanisms?

6 Types

Answer 33

• geographical isolation—physical barriers
• ecological isolation—niche partitioning within an ecosystem
• temporal isolation—differences in reproductive timing
• morphological isolation—differences in reproductive structures
• behavioural isolation (animals only)—differences in behaviours attracting mates, usually the result of sexual selection
• gamete mortality—no fertilisation by gametes.

Question 34

What is an Polyploidy mutation?

Answer 34

The cell or individual has more than two copies of every chromosome, e.g. triploid organisms have three copies of every chromosome.

Question 35

What is the Founder effect?

Answer 35

The founder effect is seen when a small group of individuals breaks away from the main population and colonises a new habitat. The founding individuals will not necessarily represent the allele frequencies seen in the original population. Further changes in allele frequencies in the founding population can arise from new environmental pressures.

Question 36

What is a Point Mutation & what are the types?

3 Types

Answer 36

A point mutation involves just one nucleotide in RNA (or nucleotide pair in DNA).

• Substitution
• Addition
• Deletion

Question 37

What traits are typically bred for in animals?

Answer 37

Animals are often bred for:

• High quality traits and products (such as wool and milk)
• Personality traits (such as loyalty in pets).

Question 38

What are genetic isolating mechanisms?

Definition + 2 types

Answer 38

Populations may also evolve into different species as a result of having become fragmented through various genetic isolating mechanisms.

Isolating mechanisms can be

• Prezygotic - preventing fertilisation of gametes of different species
• Postzygotic - preventing production of viable offspring after fertilisation.

Question 39

What is a species?

Answer 39

A species is a group of individuals that can produce viable, fertile offspring through interbreeding, and has a gene pool that is isolated from the gene pools of other species.

Question 40

What is the effect of mutations?

Answer 40

Mutations may have a beneficial effect a harmful effect or no effect at all on the individual.

Question 41

What is allopatric speciation?

Answer 41

The most common form of speciation is allopatric speciation, in which a population becomes divided by a geographical barrier. In this type of speciation. spatial isolation is the mechanism preventing gene flow, leading to genetic isolation.

Question 42

What is the downside of selective breeding?

General statement + 3 implications.

Answer 42

Selectively bred populations tend to have low genetic variation and high homozygosity, meaning that:

• they are more susceptible to environmental change
• biodiversity may be reduced if selectively bred populations replace wild populations and varieties
• an increase in the incidence of genetic abnormalities can occur.

Question 43

Whate is Allele Frequency?

Answer 43

Allele frequencies are a measure of how common a particular allele is in the gene pool of a population, and are typically expressed as percentages or decimals.

Question 44

What is a Point Substitution mutation?

Answer 44

The mutation replaces one nucleotide in the sequence for another nucleotide.

Question 45

Types of Postzygotic isolating mechanisms?

4 types

Answer 45

• hybrid inviability—the hybrid zygote does not survive
• reduced hybrid viability—the hybrid zygote survives but does not develop fully into a new individual
• hybrid sterility—the hybrid organism develops but is incapable of reproducing
• hybrid breakdown—the hybrid cannot reliably produce viable offspring.