Gene Mutations (6)

Question 1

What is a mutation?

Answer 1

A mutation is a sudden change in the genetic makeup (DNA) of an organism.

Question 2

What is a gene mutation?

Answer 2

A gene mutation results from a change in the sequence of nucleotides in a DNA molecule, causing a change in the information the gene gives to the cell, ie the codons will be altered which will result in a faulty protein or no protein at all being made.

Question 3

What are mutagens?

Answer 3

Mutations, e.g. environmental factors such as ionizing radiation (e.g. ultraviolet light and X-rays), mutagenic chemicals (e.g. formaldehyde, benzene, carbon tetrachloride) and viruses and Mutagens factors that increase the rate of microorganisms.

Question 4

What effects can mutations have on organsims? (3)

Answer 4

Mutations can have a variety of different effects on organisms depending on:

• the type of mutation
• the importance of the piece of genetic material affected - whether the affected cells are germ cells (gametes) or somatic cells.

Question 5

Where do somatic mutations occur?

Answer 5

Somatic mutations occur in body cells and are not transmitted to the next generation.

Question 6

What do somatic mutations result in for animals in comparison to plants?

Answer 6

These can cause cells to become malignant which will result in cancer. In plants, they may be transmitted by vegetative propagation such as budding.

Question 7

Where do gametic reproductive mutations occur?

Answer 7

Gametic reproductive mutations occur in the anthers or embryo sacs) and produce changes in organs (ovaries, testis, to the genes in the gametes. These mutations, also known as germ-line mutations may lead to variation in the offspring.

Question 8

What do gametic reproductive mutations result in?

Answer 8

Eventually, by accumulating these changes, a new species may evolve, a process called speciation. This plays an important role in evolution. Gametic mutations may also lead to hereditary diseases.

Question 9

What are neutral mutations?

Answer 9

Neutral mutations are changes in the DNA sequence that are neither beneficial nor detrimental to the ability of an organism to survive and reproduce.

Question 10

Every individual has some mutations but most of them will not be visible in the _____.

Answer 10

phenotype

Question 11

Some gene mutations, however, do change the physical features of the body but do not seriously affect the ___of the body, e.g. tongue rollers and non-tongue rollers.

Answer 11

functioning

Question 12

What are beneficial mutations?

Answer 12

Some mutations have a positive effect on the organism in which they occur. They are called beneficial mutations.

Question 13

A small percentage of mutations result in a change in the phenotypes, what happens if the change results in the organism adapting better to new or unfavourable conditions?

Answer 13

If the change results in organisms adapting better to new or unfavourable conditions, they will survive and breed more successfully than the rest of the population.

Question 14

How is beneficial mutation a form of natural selection?

Answer 14

This is natural selection as nature has selected the better adapted to survive and breed. In time the whole population will have the new genotype and a new species will have been formed, i.e. speciation has occurred which plays an important role in evolution.

Question 15

Which species does beneficial mutation take place most often?

Answer 15

Due to their rapid reproduction rate, beneficial mutations occur most often amongst viruses and bacteria, e.g. the new multi-resistant superbugs (bacteria) that have mutated to become resistant to antibiotics. This is obviously harmful to humans, but beneficial to the survival of the bacteria species!

Question 16

Name a classic example of beneficial mutation.

Answer 16

A classic example of a beneficial mutation is the mutation of the pale form of the peppered moth to a dark form in some parts of Great Britain during the industrial revolution. The buildings and surroundings became grey with coal dust so the grey colour of the moths made them less conspicuous to predators and enabled them to survive.

Question 17

What are harmful mutations?

Answer 17

The mutations we hear about most often are the ones that cause disease. Harmful mutations may cause genetic disorders or cancer.

Question 18

Humans have over 100 syndromes caused by ______ abnormalities, eg Down syndrome, and more than 6,000 diseases caused by the inheritance of ____ in single genes, eg cystic fibrosis, sickle cell anaemia, Tay-Sachs disease, Huntington’s disease and colour blindness, among many others.

Answer 18

chromosomal

mutations

Question 19

Diseases such as cystic fibrosis, sickle cell anaemia, Tay-Sachs disease, Huntington’s disease usually are …

Answer 19

These diseases usually are inherited as autosomal recessive traits. autosomal relates to chromosomes that are not sex chromosomes, i.e. numbers I to 22

Question 20

For harmful mutations, The ____ parents each have one normal copy of the gene and one mutated, non-functional copy.

Answer 20

heterozygous

Question 21

For harmful mutations, the ___ recessive individuals exhibit the disorder because both gene copies are non- functional and the correct gene product, a protein, is missing.

Answer 21

homozygous

Question 22

What is albinism?

Answer 22

Albinism is a rare group of inherited genetic disorders that cause the skin, hair, or iris of eyes to have little or no colour due to the partial or complete absence of the pigment, melanin.

Question 23

What is melanin?

Answer 23

Melanin protects the DNA in underlying tissues against the harmful effects of UV light.

Question 24

What is albinism caused by?

Answer 24

It is caused by a mutation of one of several autosomal genes that produce or distribute melanin. It is estimated that about one in 70 people carry the faulty gene.

Question 25

Explain how recessive monohybrid inheritance is shown in albinism.

Answer 25

The mutated allele can pass from generation to generation and only be expressed in the phenotype of the offspring if both parents have the recessive mutated gene. Individuals may have a normal phenotype but be carriers of the gene, in which case they are not affected by the condition and have a normal amount of melanin.

Question 26

What is a carrier?

Answer 26

has a recessive allele and a dominant allele in each cell therefore has a normal phenotype.

Question 27

If both parents carry the gene, there is a ____ in __chance that their child will have albinism and a one in ___ chance they will be a carrier.

Answer 27

one in four

two

Question 28

Why is it difficult for albinos to go outside?

Answer 28

Albinism is usually not life-threatening, but as the skin of an albino is extremely sensitive to the sun, they are vulnerable to sunburn and cancer which makes working outdoors virtually impossible.

Question 29

But the challenges confronting albinos do not end there: all too often they are ____, ____against and mocked by their peers. Some people believe that giving birth to an albino is the result of a curse or bewitchment in the family. Despite attempts to promote understanding, many albinos still face prejudice and ____ from the wider community and lead lonely lives. It is important that we all make every effort to protect them against such behaviour.

Answer 29

shunned
discriminated
ignorance

Question 30

Why is genetic counselling is important in terms of albinism?

Answer 30

By studying a family tree the counsellor may be able to predict whether a couple is likely to have a child with albinism. In a pedigree chart albinism occurs infrequently, often skipping one or more generations altogether.