Chapter 12 - Mutations And Gene Pools

Question 1

Define a species

Answer 1

A species is a group of individuals that share many characteristics and are able to interbred under natural conditions to produce offspring.

Question 2

What are alleles?

Answer 2

Alleles are alternative forms of a gene. The pairs of alleles that each person inherits from their parents control and determine the characteristics of that individual.

Question 3

What is a population?

Answer 3

A population is a group of organisms of the same species living together in a particular place at a particular time.

Question 4

What are geneticists and what do they do?

Answer 4

Geneticists are scientists who specialise in the study of inheritance and the characteristics of a population.

Question 5

What is a gene pool?

Answer 5

A gene pool is the sum of all the alleles in a given population.

Question 6

What is an allele frequency?

Answer 6

An allele frequency is how many times each allele of a gene occurs in the gene pool for that population.

Question 7

What are mutations?

Answer 7

When the structure of a gene has been changed resulting in a variant, often unexplained, form of gene.

which may be transmitted to subsequent generations

Question 8

What are the two types of mutations and what do they do/affect.

Answer 8

Gene mutations ; changes in a single gene so that the traits normally produced by that gene are changed or destroyed.

Chromosomal mutations ; in which all or part of a chromosome is affected.

Question 9

What is a mutant?

Answer 9

A mutant is an organism with a characteristic of a mutation.

Question 10

What are mutagens and what are some examples?

Answer 10

Mutagens or mutagenic agents are agents that increase the rate at which mutations occur. Some examples are mustard gas, Sulfur dioxide, ultraviolets light, X-rays.

Question 11

What are the differences between somatic and germline mutations?

Answer 11

Somatic mutations are when mutations occur to body cells or somatic cells. The reproductive cells are not affected and the mutation is not usually passed on.

Germinal or germline mutations affect the gametes and can be passed down to future generations. It isn’t always evident in the individual who passes it down.

Question 12

What is point mutation?

Answer 12

Point mutation is a change in one nucleotide that can alter a protein, have no effect at all, or prevent the protein from being produced.

Question 13

What are some examples of gene mutations?

Answer 13

• Albinism
• The duchenne form of muscular dystrophy. The disease results in a wasting of leg muscles that later spread to the arms, shoulders and chest. Boys with the disease are unlikely to live for more than 25 years.
• Cystic fibrosis. Occurs on the gene in chromosome 7. It makes up the protein that regulates the passage of chloride ions across the cell membrane. The allele is recessive.

Question 14

What are lethal recessives?

Answer 14

Lethal recessives are mutations not masked by a dominant allele.
They are mutations that affect the function of an essential gene.
These mutations cause the death of the foetus or embryo.

Question 15

What are chromosomal mutations?

Answer 15

Chromosomal mutations involves all or part of a chromosome, there affecting a large number of genes.

Question 16

What are the 4 types of chromosomal mutations?

Answer 16

• Deletion ; parts of a chromosome is lost.
• Duplication ; a section of a chromosome occurs twice.
• Inversion ; breaks occur in the chromosome and the broken piece joins back in, but the wrong way around.
• Translocation ; part of a chromosome breaks off and is rejoined to the wrong chromosome.

Question 17

What is non disjunction?

Answer 17

During meiosis, a chromosome pair does not seperate and so one daughter cell has an extra chromosome and one daughter cells has one less than the normal. These are sometimes not referred to as mutations but rather aneuploidy ( a change in the chromosome number).