chapter seven: genetic changes in population over time

Question 1

define gene pool

• including the term allele

Answer 1

a gene pool is all the alleles present in a population

Question 2

state how to determine whether evolution has occurred

Answer 2

Fossils of past species that have been active once in the past are not present currently show that they are relevant to current-day species

Question 3

name and describe the three types of point mutations

Answer 3

point mutations are when bases are changed in a person’s DNA sequence

• silent mutations: the mutation has no effect
• nonsense mutation: the mutation stops the protein from being made (becomes a stop codon)
• missense mutation: the mutation changes an amino acid

Question 4

define silent mutation

• state the impact on the amino acid

Answer 4

a type of mutation in which a single base change does not change the amino acid and final protein expressed

Question 5

define nonsense mutation

• state the impact on the amino acid

Answer 5

a type of mutation that codes for a stop in the amino acid chain resulting in a shortened polypeptide to be formed

Question 6

define missense mutation

• state the impact on the amino acid

Answer 6

a type of mutation that changes one amino acid to another

Question 7

explain why insertion and deletion mutations are called frameshift

Answer 7

frameshift mutations:

• alter the base sequence of a gene so that the message it encodes no longer makes sense
• this is referred to as changing the reading frameshift
• insertion and deletions are frameshift as for it changes the amino acid sequence which encodes for something that doesn’t make sense

Question 8

name and describe the four types of block mutations

Answer 8

• deletion of a part of a chromosome
• duplication or gain of part of a chromosome
• translocation exchange between non-homologous chromosomes
• inversion when a segment of a chromosomes rotate

Question 9

state how mutations could bring about new alleles

Answer 9

it can create new DNA sequence for a particular gene

Question 10

give examples of environmental selection pressures

Answer 10

physical

• climate change
• shelter
• food availability

biological

• competition
• predators
• disease

chemical

• pollutants
• drugs (antibiotics)

Question 11

state how selection pressures can cause a change in the allele frequency in a gene pool

Answer 11

selection pressure acts on the phenotype and changes the genotype (gene pool - allele frequencies)

selection pressures leads to natural selection

• natural selection occurs when any selecting agent acts on a population creating a selective advantage for particular phenotype (therefore genotype)
• the differences in survival and reproduction results in changes to allele frequencies —> evolution

Question 12

describe the potential effects of gene flow (migration) on gene pools

Answer 12

they are transferring their alleles from one gene pool to another

• the movement of alleles can increase the genetic diversity of a population when a new allele is introduced

Question 13

define genetic drift (bottleneck effect and founder effect) using examples

Answer 13

genetic drift:

• variation in the relation frequency of different genoypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce

bottleneck:

• a phenomenon in which a population is reduced in size due to natural disasters, habitat loss, or overhunting

founder:

• the reduction in genomic variability that occurs when a small group individuals become separated from a larger population

Question 14

compare natural selection to genetic drift

Answer 14

genetic drift is caused by random chance due to sampling errors, while natural selection is survival of the fittest

Question 15

give an example of when increasing genetic diversity can benefit a population

Answer 15

when the population isn’t suited for the environment

Question 16

give an example of when decreasing genetic diversity can benefit a population

Answer 16

when the diversity/variation is already suited for the environment

Question 17

give an example of when increasing genetic diversity can be detrimental to a population

Answer 17

when a population is perfectly suited for the environment and a mutation occurs, leading to the population of the species to decline

Question 18

give an example of when decreasing genetic diversity can be detrimental to a population

Answer 18

when the environment isn’t suitable for the population, and if genetic diversity continues to decrease, then a sudden factor can eliminate all of the population

Question 19

describe how humans can select for traits through breeding

Answer 19

humans can choose the traits that they like and breed it with another trait that they like

Question 20

give examples of when and why humans have used selective breeding

Answer 20

dogs: humans have breed small dogs so that they remain small throughout the rest of their life and still look cute

Question 21

state the effect of selective breeding on genetic diversity

Answer 21

it decreases genetic diversity because there would only be a few genes left because they are considered ‘favourable’ to humans

Question 22

state 3 differences between natural selection and selective breeding

Answer 22

Natural Selection:

• traits are selected by the likelyhood of them surviving
• increase the genetic diversity
• chosen by nature

Selective Breeding:

• traits are chosen by their likeability
• decrease the genetic diversity
• chosen by humans

Question 23

explain how bacteria can become resistant to antibiotics

Answer 23

through mutations and selections, bacteria can become resistant to antibiotics

Question 24

compare antigenic drift to antigenic shift

Answer 24

antigenic shift

• occurs faster
• viruses swap their DNA to become new viruses

antigenic drift

• mutation occurs more slower
• small changes in one protein due to point mutation