6.1 Cellular Control

Question 1

what is a mutation

Answer 1

random change to the genetic material

Question 2

when can mutations occur

Answer 2

during DNA replication before cell division

Question 3

what things can cause mutations

Answer 3

certain chemicals like tar in tobacco smoke, ionising radiation like UV, X Ray, gamma rays

Question 4

what does mutagenic mean

Answer 4

causing permanent DNA changes or mutation in the cell

Question 5

what is a mutation called that happens with mitotic divisions

Answer 5

somatic mutations - they are not passed to offsprings

Question 6

what mutations can be inherited by offspring

Answer 6

mutation associated with meiosis and gamete formation

Question 7

what are the 2 main classes of DNA mutation

Answer 7

point mutation and insertion/deletion (indel) mutation

Question 8

what is a point mutation

Answer 8

one base pair is substituted for another

Question 9

what is an insertion or deletion mutation

Answer 9

1 or more nucleotides are inserted or deleted from a length of DNA (this could cause a frameshift)

Question 10

how many types of point mutations are there and what are they called

Answer 10

3 types - silent, missense and nonsense

Question 11

what is a mutagen

Answer 11

a substance causing mutation and can increase mutation rate

Question 12

how is the effect of point mutations reduced and what is this called

Answer 12

the amino acids involved in protein synthesis have more than 1 base triplet code - called redundancy or degeneracy

Question 13

what is a silent mutation (in point mutations)

Answer 13

changes to the base triplet where the triplet still codes for the same amino acid

Question 14

does the primary structure of the protein change in a silent mutation

Answer 14

no - because remember there are more than 1 triplet codes for the amino acids and therefore the secondary and tertiary structure is not altered

Question 15

what is a missense mutation

Answer 15

change to the base triplet sequence that leads to a change in the amino acid sequence in a protein

Question 16

does the structure of a protein change in missense mutations

Answer 16

yes - because the primary structure of the protein is changed and this leads to changes in the tertiary structure

Question 17

what type of anaemia results from a missense mutation

Answer 17

sickle cell anaemia - causes changes to the B-polypeptide chains of haemoglobin therefore causing sickle shaped, blocking capillaries and depriving tissues of oxygen

Question 18

what is a nonsense mutation

Answer 18

there could be a termination after a base triplet so it becomes a termination triplet - results in a truncated protein that will not function and the abnormal protein will most likely be degraded within the cell

Question 19

what do indel mutations cause

Answer 19

frameshifts

Question 20

what is a frameshift

Answer 20

nucleotide bases pairs are inserted or deleted from the gene - because the code is non-overlapping and read in 3 base groups, all the subsequent base triplets are altered

Question 21

what happens to the protein in an indel mutation

Answer 21

the amino acid after the frameshift is severely disrupted and so the primary, secondary and tertiary structure is altered therefore the protein is abnormal and cannot carry out its normal function

Question 22

what type of haemoglobin disorder results from frameshifts due to deletion and insertion of bases

Answer 22

thalassaemia

Question 23

what is an expanding triplet nucleotide repeat

Answer 23

the number of triplets increases at meiosis again and again from generation to generation - huntington’s disease results from this

Question 24

are all mutations harmful?

Answer 24

no - some are good and have driven evolution through natural selection

Question 25

what is an exon

Answer 25

coding or expressed region of DNA

Question 26

what is an intron

Answer 26

non-coding region of DNA

Question 27

what is an operon

Answer 27

group of genes that function as a single transcription unit - first identified in prokaryotic cells

Question 28

what is a transcription factor

Answer 28

protein or short non-coding RNA that can combine with a specific site on a length of DNA and that can inhibit or activate transcription of the gene

Question 29

what does E Coli do when there is no available glucose for respiration

Answer 29

if lactose is present, then it will induce the production of 2 enzymes lactose permeate - allows lactose to enter bacterial cell Beta-galactosidase - hydrolyses lactose to glucose and galactose

Question 30

how are the 2 enzymes actually coded for in the DNA

Answer 30

the lac operon has an operating region lacO next to the structural genes lacZ and lacY that code for both the enzymes

Question 31

what is next to lacO

Answer 31

the promoter region P - which enzyme RNA polymerase binds to to begin transcription of the structural genes lacX and lacY

Question 32

what is the homeobox gene sequence

Answer 32

sequence of 180 base Pais (excluding introns) found within genes that are involved in regulating patterns of anatomical development within animals, plants and fungi

Question 33

what are hox genes

Answer 33

subset of homeobox genes specifically controlling anatomical development in animals only (like which body part grows wear)

Question 34

what is colinearity

Answer 34

sequential and temporal order of gene expression corresponds to sequential and temporal development of various body parts

Question 35

how are Hox genes regulated

Answer 35

gap genes and pair-rule genes that are further regulated by maternally supplied mRNA from the egg cytoplasm

Question 36

what can Hox genes help regulate

Answer 36

mitosis (part of the cell cycle) - ensuring that each daughter cell contains the full genome and is a clone of the parent cell

Question 37

what is apoptosis

Answer 37

programmed cell death

Question 38

sequence of events during apoptosis

Answer 38

1. enzymes break down cell cytoskeleton 2. cytoplasm becomes dense with organelles 3. cell surface membrane changes and small protrusions called blebs form 3. chromatin condenses, nuclear envelope breaks and DNA breaks into fragments 5. Cell breaks into vesicles that are ingested by phagocytes so cell debris does not damage any other cells or tissues

Question 39

how is apoptosis controlled

Answer 39

through veery good cell signalling and response to internal and external stimuli such as stress signalling molecules also include cytokines from the immune system, hormones, growth factors and nitric oxide

Question 40

how is apoptosis an integral part of animal and plant tissue development

Answer 40

during limb development, apoptosis separates the digits (like toes) removes harmful T-lymphocytes during formation of the immune system rate of cells dying = rate of cells produced by mitosis otherwise tumours (too little apoptosis) or cell loss and degeneration (too much apoptosis)