Chapter 7.7

Question 1

MUTATION

Answer 1

Is a change in a cell’s DNA’ sequence ( either in a protein coding gene or in non- coding DNA such as an enhancer.)

Question 2

Th significance of mutations

Answer 2

1. they change the structure of its encoded protein so that it can no longer do its job.
2. They provide genetic variability. they are the raw materials for evolution because they create new alleles

Question 3

ALLELES

Answer 3

Mutatation create new alleles. They are a variation of a gene.

Exceptfor identical twins we all have different combinations of for all our genes

Question 4

POINT MUTATION

Answer 4

Substitution of one DNA base for another

Question 5

SUBSTITUTION MUTATION

Answer 5

It is the replacement of one DNA base with another.

It is a silent mutation

Question 6

SILENT MUTATIONS

Answer 6

When a mutation occurs but the mutated gene still encodes the same protein as the original gene version.

They occur because more than one codon encodes most amino acids

Question 7

MISSENSE mutation

Answer 7

occurs when a substition mutation changes a base triplet so that it specifies a different amino acid.
This may drastically change the protein’s shape and thus its function

Question 8

NONSENSE MUTATIONS

Answer 8

A base triplet specifying an amin acid changes into one that encodes a stop codon (cystic fibrosis)

Question 9

3 types of POINT MUTATIONS

Answer 9

1. SUBSTITUTION MUTATIONS
2. BASE INSERTIONS AND
3. DELETIONS

Question 10

2 Types of SUBSTITUTION MUTATIONS

Answer 10

1. MISSENSE- specifies for a different amino acid changing the shape of the the protein
2. Nonsense cause the base to to code for a “ stop”codon shortening the polypeptide

Question 11

eg. BASE INSERTIONS AND DELETIONS

Answer 11

FRAMESHIFT MUTATION

Question 12

FRAMESHIFT MUTATION

Answer 12

adds or deletes nucleotides in any number other than a multiple of three changing the reading frame and altering the amino acid sequence.

Question 13

EXPANDING REPEAT MUTATION

Answer 13

the number of copies of 3 or 4 nucleotides sequence increases over several generations.
With each generation the symptoms begin earlier or more sever ,or both.

Question 14

REPLICATION ERRORS/ SPONTANEOUS SUSTITUTION MUTATON

Answer 14

usually originates a DNA replication error.

Replications errors can also cause insertions and deletions, especially ingenues with repeated base sequences.

Question 15

MUTAGEN

Answer 15

Is any external agent that induces mutations
Egs
UV radiation, X-rays, nuclear accidents, chemicals

Question 16

List the causes of mutations

Answer 16

1. Spontaneous substitution mutation/addition and deletion= Replication Errors
2. Mutagens
3. Errors in Meiosis ( misalignment at at crossover point)
4. Inverted chromosomes
5. two different chromosomes fusing together
6. TRANSPOSABLE ELEMENT

2.

Question 17

TRANSPOSABLE ELEMENT MUTaTIONS

Answer 17

or TRANSPOSON is a Dna sequence that can jump within the genome.

It can insert itself randomly into chromosomes disrupting a gene’s function or leaving a gap in a gene when it leaves.

Question 18

GERMLINE MUTATION

Answer 18

occurs in the cells that give rise to sperm and eggs

Question 19

Why are germline mutations heritable

Answer 19

They are heritable because mutated Dna will be passed down to at least some of the sex cells that the organism produces

Question 20

the result of inheriting a germ line mutation

Answer 20

every cell in that organism produces

Question 21

Non heritable mutations

Answer 21

SOMATIC MUTATIONS

Question 22

SOMATIC MUTATIONS

Answer 22

occurs in non sex cells.
They are non- heritable
The mutation is not passed down to their offsprings

Question 23

Why are mutations important

Answer 23

1. They produce genetic variability
2. They are raw materials for evolution because they create new alleles
3. Homeotic genes
4. Improves reproductive success in some species ( bacteria)
5. Allow some viruses to jump from animal to humans
6. Induced mutations create crop variety

Question 24

ALLELES

Answer 24

Variants of a gene

Except for identical twins everyone has a different combination of genes

Question 25

Allele combinations and fitness

Answer 25

In every species individuals with some allele combination reproduce more successfully than others
NATURAL SELECTION EDITS OUT THE LESS FAVORABLE ALLELE COMBINATIONS

Question 26

HOMEOTIC GENES

Answer 26

They cause the development of specific structures in plants and animals. They control the pattern of body formation during early embryonic development

They encode transcription factors that are expressed during the development of an embryo. If the transcription factors are faulty, the signals that control the formation of an organism’s body part become disrupted

Question 27

how have HOMEOTIC genes affected animal evolution

Answer 27

limb modifications trace their origins to homeotic mutations

Question 28

e.g. of how mutations enhance an organisms reproductive success

Answer 28

Antibotic Resistant Bacteria ( offsprings are are unaffected by antibiotic drugs)

2. ramdom mutations in viral genomes enable viruses to jump from other animals to humans
3. Scientist induce mutations to learn how normal genes function
4. they are also induced to create variety

Question 29

What is a mutation?

Answer 29

A mutation is a change in the DNA sequence of a cell.

Question 30

What are the types of mutations, and how does each alter the encoded protein?

Answer 30

A point mutation changes one or a few base pairs of genes. Point mutations include substitution mutations (which replace one DNA base for another), insertions, and deletions. Substitution mutations might change one amino acid to another in the encoded protein (which is called a missense mutation), might change an amino acid to a stop codon (which is called a nonsense mutation), or might not change an amino acid (which is called a silent mutation). Insertions of deletions of more or fewer than three nucleotides will shift the “reading frame” of the gene; these frameshift mutations might alter many amino acids in the protein, drastically changing its shape and function. An insertion of three nucleotides adds one amino acid to the encoded protein. A deletion of three nucleotides removes one amino acid from the encoded protein. Expanding repeat mutations increase the number of copies of three-or four-nucleotide sequences over several generations. This causes extra amino acids to be inserted into a protein, deforming it.

Question 31

What causes mutations

Answer 31

Mutations are caused by DNA replication errors, errors in crossing over during meiosis, chromosome inversions and translocations, or exposure to chemicals or radiation.

Question 32

. What is the difference between a germline mutation and a somatic mutation?

Answer 32

A germline mutation is one that occurs in a cell that will give rise to a sperm or an egg cell. A somatic mutation occurs within a non-germline body cell.

Question 33

How are mutations important?

Answer 33

Mutations are used to learn how genes normally function and to develop new varieties of crop plants. Mutations can also be used to trace the evolution of viruses and other infectious agents.

Question 34

Why can silent mutations occur

Answer 34

Because more than one codon encodes most amino acids