UNIT 4 ➜ SAC 3 (Changes in a pop. over time)

Question 1

Define Mutation

Answer 1

A change in the genetic information of an organism

Question 2

Define Point mutation

Answer 2

Change to a single base pair

Question 3

List the 4 types of Substitution Point mutations + DEFINE them

Answer 3

Silent mutations - Does not alter the amino acid sequence, as the DNA/triplet code is redundant

Missense mutations - Change in the base alters the triplet codon, resulting in a different amino acid

Nonsense mutations - Change in the base alters the triplet codon to a STOP codon

Frameshift - Insertion or depletion of a base result in all further triplet codons being altered

Question 4

Define Block mutation

Answer 4

Changes to whole segments of a chromosome

Question 5

List the 4 types of Block mutations + DEFINE them

Answer 5

Duplications - Part of the chromosome is copied, resulting in duplicate sections

Deletions - A segment of the chromosome is removed (along with any genes contained in the segment)

Inversions - A segment of the chromosome is removed and is replaced within the chromosome in reverse order

Translocations - Segments of 2 chromosomes are exchanged

Question 6

Compare
- Monoploidy
- Polyploidy
- Aneuploidy

Answer 6

Monoploidy - Contains 1 copy of each chromosome

Polyploidy - Contains multiple copies of each chromosome

Aneuploidy - The addition or loss of 1 chromosome

Question 7

Define Gene pool

Answer 7

Complete set of alleles present in a pop.

Question 8

Define Selection pressures

Answer 8

A factor that favours the survival of some individuals over others in a population

Over time the environment acts on the phenotypes of individuals = altering the allele frequency in the pop.

Question 9

Provide some examples of Selection pressure

Answer 9

• Competition for living space/shelter/food
• Predators
• Human interference
• Changes in the environment
• Parasites
• Disease causing micro organisms

Question 10

Define Biological fitness

Answer 10

The extent to which an individual is able to survive + produce offspring in a particular environment

Question 11

Define Gene flow

Define Genetic drift

Answer 11

Exchange of alleles between populations due to migration

Changes over time due to random, non-selective events

Question 12

Define Founder effect

Define Genetic bottleneck

Answer 12

When a small proportion of individuals from the original population form a new population

A large population’s numbers reduce dramatically, reducing genetic variability

Question 13

Antigenic Drift VS Antigenic Shift

Answer 13

DRIFT - Accumulation of a series of minor genetic mutations (Changed appearance of surface antigens)

SHIFT - An abrupt major change that involves the ‘mixing’ of genes from different viruses (Produces a new strain or a different virus)

Question 14

Define the 3 types of Selection
- Natural
- Sexual
- Artificial

Answer 14

NATURAL - Individuals with the most favourable characteristics have the best chance of surviving and reproducing

SEXUAL - A type of Natural selection that impacts mating behaviour

ARTIFICIAL - Involves human intervention in plants or animals to select for desirable characteristics

Question 15

Natural Selection Question scaffold
** MEMORISE

HINT - Bold in adapted/changed for the question

Answer 15

Heritable variation exists in 𝐚 𝐩𝐨𝐩𝐮𝐥𝐚𝐭𝐢𝐨𝐧 for 𝐚 𝐩𝐚𝐫𝐭𝐢𝐜𝐮𝐥𝐚𝐫 𝐭𝐫𝐚𝐢𝐭

𝐒𝐞𝐥𝐞𝐜𝐭𝐢𝐨𝐧 𝐩𝐫𝐞𝐬𝐬𝐮𝐫𝐞𝐬 applied to the population cause a 𝐩𝐡𝐞𝐧𝐨𝐭𝐲𝐩𝐞 to be more advantageous than others, allowing them higher rates of survival and reproduction than others

Over many generations, the alleles underlying the 𝐚𝐝𝐯𝐚𝐧𝐭𝐚𝐠𝐞𝐨𝐮𝐬 𝐩𝐡𝐞𝐧𝐨𝐭𝐲𝐩𝐞𝐬 are passed on at higher frequencies than their counterparts, and eventually, the 𝐚𝐝𝐯𝐚𝐧𝐭𝐚𝐠𝐞𝐨𝐮𝐬 𝐩𝐡𝐞𝐧𝐨𝐭𝐲𝐩𝐞 becomes more prevalent

Question 16

Another Natural Selection Question scaffold

Answer 16

Variation in a population - Selection pressure acts on different phenotypes - Differences in Biological fitness - Those with higher biological fitness are able to survive and reproduce, passing their alleles onto the next generation

Question 17

Founder effect and Genetic bottleneck
- What are the effects of limited variation?

Answer 17

Inbreeding – Mating between related individuals becomes more prevalent (Keeps harmful alleles in the gene pool)

Decreased adaptive potential – Less chance of individuals having alleles that allow them to cope with new selection pressures

Increased risk of extinction of a population

More subject to genetic drift

Question 18

What are the 3 types of effects that Mutation can have?

Answer 18

Neural mutations - Has no effect on an organism’s chances of survival and reproduction

Deleterious mutations - Decreases an organism’s chance of survival

Beneficial mutations - Increases an organism’s chance of survival

Question 19

How is Variation generated?
HINT - 2 ways

Answer 19

Mutations

Sexual reproduction (Meiosis, Random union of gametes etc.)

Question 20

Antibiotics and Natural Selection?

Answer 20

Pre-existing variation exists in a bacteria population - Antibiotic acts as a selective agent - Bacteria with antibiotic resistance are able to survive, grow and reproduce (due to a higher biological fitness)

Question 21

Define Evolution

Answer 21

Changes in the allele frequencies of a population over time

Question 22

What are Allele frequencies?

Answer 22

The proportion of an allele within a population
(Ranges from 0-1)