Mutation and Variation

Question 1

What are the three causes of a change in the sequence of genes.

Answer 1

Substitution, deletion and insertion.

Question 2

What is substitution with regards to genes

Answer 2

Only alter one codon, replacing one nucleotide base with a different nucleotide base, point mutation

Question 3

What is insertion with regards to genes

Answer 3

placing one nucleotide before another, frame shift

Question 4

What is deletion with regards to genes

Answer 4

deleting one nucleotide from the polypeptide chain, frame shift

Question 5

What is mutation

Answer 5

A change in a genes or chromosomes structure, rare, spontaneous, random

Question 6

What is a mutagen

Answer 6

A chemical or physical agent that causes mutation (cigarettes, radiation, diseases/viruses)

Question 7

What are the two categories of mutation

Answer 7

Gene mutation - single gene

A chromosome mutation - affects a single chromosome or set of chromosomes

Question 8

Where does silent mutation usually happen?

Answer 8

usually in the non-coding part of the DNA

Question 9

Examples of harmful mutations

Answer 9

70% of cystic fibrosis sufferers, the mutation is a deletion of a triplet of base pairs.

Protooncogenes can be changed into, oncogenes by a point mutation which promote uncontrolled cell division.

Huntington disease is caused by a stutter, this repeating sections of CAG sequences.

Question 10

Sickle cell anemia characteristics.

Answer 10

A mutation in the gene coding for the beta chain, single point mutation.

Pulled out of bi-concave shape due to there being valine instead of glutamate. Less O2.

Question 11

What is the lac operon?

Answer 11

an operon is a group of genes that are under the control of the same regulatory mechnaism and are expressed (or not) at the same time

E.coli can form enzymes that can breakdown lactose, these enzymes do not want to be created if not needed. (B-galactosidase, Lactose permease)

Regulator gene is expressed and produced repressor protein which stops RNA polymerase from binding to operating region, no gene Z or gene Y expressed. (NO LACTOSE PRESENT)

Lactose binds to second binding site of repressor protein, changing tertiary 3d shape, Repressor protein cannot bind to operator region, RNA Binds to operator region expressing Z and Y. (LACTOSE PRESENT)

Question 12

What are the different genes in the lac operon?

Answer 12

I: regulatory gene for lac operon

P: Promoter region RNA polymerase binds here to start transcription of Z+Y

O: Operator region, switches Z+Y off or on

Z: Codes for B-galactosidase

Y: Codes for lactose permease

Question 13

What is a homeobox gene

Answer 13

It determines how an organisms body develops as it grows from a zygote into a complete organism, determining the organisms body plan.

Question 14

How is development mediated by homeobox genes?

Answer 14

Maternal effect genes - determine the embryo’s polarity, anterior and posterior

Segmentation genes - determine polarity of each segment

Homeotic selector genes - identify and direst the development of each segment.

Question 15

What is Antp within a fruit fly?

Answer 15

If Antp is usually turned on in the thoraz, allowing normal legs to develop

If turned on in head, legs will grow instead of antennae.

Question 16

What do homeobox genes do?

Answer 16

Homeobox genes code for the production of transcription factors, these proteins can bind to a particular region of DNA and cause it to be transcribed.

Question 17

What is apoptosis?

Answer 17

Programmed cell death which can act as a mechanism to change body plans. It is a series of biochemical events leading to an orderly and tidy cell death.

Question 18

What is Hayflick’s constant

Answer 18

Cells undergo about 50 mitotic divisions before apoptosis.

Question 19

What is necrosis

Answer 19

Untidy and damaging cell death occurring after trauma

Question 20

What is the sequence of apoptosis?

Answer 20

Enzymes break down cytoplasm
Cytoplasm becomes dense
Organelles are tightly packed
Cell surface membrane changes and blebs form
Chromatin condenses, nuclear envelope breaks
Cell breaks into vesicles
Phagocytosis.

Question 21

How is apo cytosis controlled

Answer 21

Cell signaling, such as cytokines, hormones, growth factors and nitric oxide (makes inner mitochondrial membrane more permeable to hydrogen ions, stopping respiration)

Question 22

The rate of cell death should be equal too…

Answer 22

The rate of mitosis. (if this is not the case tumors can form).

Question 23

What is point mutation?

Answer 23

Where only one nucleotide is affected during a mutation.

Question 24

What is a frameshift mutation?

Answer 24

Occurs during insertion or deletion, changing the reading of every successive codon after the point of mutation

Question 25

What is an example of a physical mutagen?

Answer 25

Ionizing radiations like x rays

Question 26

What is an example of a chemical mutagen?

Answer 26

Deaminating agents

Question 27

What is an example of a physical mutagen?

Answer 27

Viruses

Question 28

What are some examples of changes of a chromosomes structure due to mutation?

Answer 28

Deletion Duplication Translocation - a section of one chromosome breaks of and joins another non-homologous chromosome Inversion- a section of chromosome breaks off, is reversed, and then joins back onto the chromosome/

Question 29

What is translocation with reference to chromosome mutation

Answer 29

Translocation - a section of one chromosome breaks of and joins another non-homologous chromosome

Question 30

What is inversion with reference to chromosome mutation

Answer 30

Inversion- a section of chromosome breaks off, is reversed, and then joins back onto the chromosome