Module 6: Section 1 - Cellular Control

Question 1

What is a gene mutations

Answer 1

Mutations are changes to the base sequence in the DNA.

Question 2

What causes mutations

Answer 2

Mutations can be caused by insertion, deletion and substitution of bases.

Question 3

Why are mutations harmful

Answer 3

They can interrupt the normal functioning of a protein

Question 4

What are insertion mutation

Answer 4

When one or more bases are added to the DNA sequence

Question 5

What are deletion mutations

Answer 5

When one or more bases are removed from the DNA sequence

Question 6

What are substitution mutations

Answer 6

When one or more bases are changed in the DNA sequence

Question 7

What are mutagenic agents

Answer 7

They increase the rate at which mutations occur

Question 8

What are chromosomal mutations

Answer 8

mutations that affect the whole chromosome/ number of chromosomes in the cell

Question 9

What are the positive effects of mutation

Answer 9

In adults the mutation in the lactase gene allows it to breakdown lactose

Question 10

What are the negative effects of mutations

Answer 10

Mutations in the gene coding for haemoglobin causes sickle cell anaemia

Question 11

What are the neutral effects of mutations

Answer 11

Mutations which change the triplet of bases but still codes for the same amino acid

Question 12

What are operons

Answer 12

A cluster of genes under the control of a promoter.

Question 13

What are the types of regulatory molecules that can affect the expression of operons

Answer 13

Repressors: proteins which supress transcription
Activators: proteins that increase transcription
Inducers: activate or repress transcription depending on the needs of the cell and substrate availability

Question 14

What is Lac operon

Answer 14

-the lac operon is an inducible operon which contains the genes necessary to acquire and process lactose from the environment

Question 15

Explain what a lac operon does

Answer 15

-Regulatory gene codes for the repressor protein
-when lactose is present it binds to the repressor protein
-the repressor protein then changes shape which stops it from binding to the operator so RNA polymerase can now bind to the promoter

Question 16

What happens in regulation of gene expression

Answer 16

• Methylation of DNA and histones cause DNA to pack tightly together stopping transcription factors from binding to the DNA
  -Histone acetylation results in loose packing of nucleosomes, allowing transcription factors to bind to DNA and genes to be expressed
  -RNA polymerase and transcription factors bind to the promoter region located upstream of the gene, to initiate transcription

Question 17

What is RNA splicing (post transcriptional level)

Answer 17

-After transcription the RNA has regions which don’t code for proteins (introns) which are removed prior to translation
-activated by cAMP

Question 18

What happens at post translational level

Answer 18

-some proteins need to be activated before they can work by hormones and sugars
-some of these molecules work by binding to cell membrane and stimulating the production of cyclic AMP
-cAMP activates the protein by changing its 3D structure and also by protein kinases which activates proteins by phosphorylation

Question 19

What are Homeobox genes

Answer 19

is a group of regulatory genes(products switch on and off other genes)

Question 20

How long are homeobox gene sequences

Answer 20

180 base pairs in length

Question 21

What allows homeobox genes to bind to DNA

Answer 21

Homeodomain

Question 22

What does conserved mean in terms of homeobox genes

Answer 22

Little variation between animals plants and fungi with little variation in the DNA sequence

Question 23

What are HOX genes

Answer 23

Are particular type of homeobox genes in animals that are responsible for the position of the body parts

Question 24

What is the function of HOX genes

Answer 24

They code for proteins that act as transcriptional factors which can lead to genes being repressed or activated

Question 25

What is apoptosis

Answer 25

Apoptosis is the programmed death of cells

Question 26

why is apoptosis necessary

Answer 26

-Cell death is sometimes required in order for an organism to develop and grow further -Is also crucial in stopping the spread of infection

Question 27

What is a gene

Answer 27

A section of DNA that codes for a polypeptide

Question 28

What is a polypeptide

Answer 28

a chain of amino acids joined together by a peptide bond

Question 29

What is a protein

Answer 29

1 or more polypeptide chains folded

Question 30

What is a genome

Answer 30

all genetic information of an organism includiing genes and non coding DNA

Question 31

What is a histone

Answer 31

protein that DNA wraps around to form chromatin and allows DNA to be more compactly packaged

Question 32

What are the types of mutations

Answer 32

Gene and chromosomal

Question 33

What is a gene mutation

Answer 33

changes to base sequence of genes in DNA

Question 34

what are the types of gene mutation

Answer 34

-insertion, substitution and deletion

Question 35

What are the 3 subtypes of substitution mutation

Answer 35

-mis-sense, nonsense and silent

Question 36

What do insertions and deletions cause

Answer 36

-frameshift which is where the sequence isn't read as it normally would be and every codon after the mutation is affected -protein will have a different sequence of amino acids and so tertiary structure

Question 37

What is a mis sense

Answer 37

where a substitution causes a different amino acid to be coded for

Question 38

What is a nonsense

Answer 38

where one base is substituted with another and this causes a stop codon to be created

Question 39

What is a silent

Answer 39

When a substitution occurs that has no effect on the amino acid coded for due to the degenerate nature of the code

Question 40

What are the types of chromosomal mutations

Answer 40

-Deletion( when a section of chromosome breaks off and is lost within the cell) - duplication (when sections or the whole chromosome are duplicated) -translocation (a section of one chromosome breaks off then joins another non homologous chromosome -inversion (a section of one chromosome breaks off, is revered and joins back to the chromosome

Question 41

what are introns

Answer 41

non coding regions inside genes

Question 42

what are exons

Answer 42

coding regions

Question 43

What does the homeobox code for

Answer 43

Homeodomain which are proteins that bind to DNA or other parts of DNA to switch on and off genes

Question 44

What is the apoptosis mechanism

Answer 44

-cytoskeleton broken down so the cell looses its shape -Blebs form due to changes in the cell surface membrane -blebs form segments which are digested by phagocytosis

Question 45

Why does sometimes apoptosis not occur

Answer 45

hox gene does not produce transcription factor / transcription factor not activated so molecules signalling apoptosis not produced so apoptosis (to separate fingers) does not occur

Question 46

Suggest two reasons why …. are chosen as a suitable species for investigation.

Answer 46

its cheap easy to keep

Question 47

Explain why some regions of DNA can be described as ‘non-coding’

Answer 47

-editing of primary, mRNA / transcript ✓ -not present in mature mRNA ✓ -not translated ✓ -regulatory, sequences / genes ✓

Question 48

What are the types of adaptation

Answer 48

anatomical, behaviour and physiological

Question 49

Explain how it is possible for a mutation to have no effect on the protein produced from that gene.

Answer 49

- some triplets code for the same amino acid (degenerate) -so the amino acid sequence is not altered -some alternative amino acids will not alter the shape of the protein -mutations occurs in introns

Question 50

Explain how a mutation could alter the protein so that it no longer performs its correct function in the cell.

Answer 50

-an insertion/deletion will cause a frame shift -all triplets downstream will be different -the protein will have a different sequence of amino acids -the tertiary structure will be different