Module 6.1.1 - Genetics of living systems

Question 1

What are the 4 types of DNA mutations that can happen?

Answer 1

• substitution
• insertion
• deletion
• frame shift

Question 2

What is substitution?

Answer 2

• changes nucleotide/base for another
• could code for another amino acid
• structure/bonds could change
• could change function

Question 3

What are the 3 types of substitution and what do they do?

Answer 3

Nonsense - mutation results in 1 of the 3 stop codons, protein is shorter, wont fully be effective, stop working

Missense - different amino acid sequence being coded for

Silent - change to base makes no difference, no effect had on amino acid and protein

Question 4

What is insertion?

Answer 4

• extra nucleotide added in
• changes all codons after it
• could change all amino acid

Question 5

What is deletion?

Answer 5

• nucleotide is removed
• could change all amino acids
• changes all codons after it

Question 6

What is frame shift?

Answer 6

• caused by deletion and insertion
• cause all further amino acids to be changed
• some change shape/shorter

Question 7

What is an example of a substitution mutation?

Answer 7

Sickle cell anaemia
- swapping A for T in a gene for haemoglobin
- structure of red blood cells change

Question 8

What are the effects of mutations?

Answer 8

Neutral - normal functioning proteins still synthesised, phenotype of organism is unchanged

Harmful - proteins not synthesised or are non functional, phenotype of organism is negatively impacted

Beneficial - protein synthesised with a new and useful characteristic and phenotype

Question 9

What are some causes of mutations?

Answer 9

• radiation
• x rays
• chemicals in cigarettes smoke
• chemicals in caffeine
• UV light

Question 10

What is an operon?

Answer 10

Section of DNA that contains cluster of genes that’re all transcribed together as well as control elements and a regulatory gene
- more common in prokaryotes than eukaryotes

Question 11

What is a Lac Operon?

Answer 11

Only produce enzymes needed to respire lactose when present, if not, repressor is present to stop lactose being produced

Question 12

What are the parts of the Lac Operon when its turned off?

Answer 12

• regulatory gene
• promotor
• operator
• structural genes
• RNA polymerase
• active repressor
• mRNA
• DNA

Question 13

What are the parts of the Lac Operon when its turned on?

Answer 13

• regulatory gene
• promotor
• operator
• RNA polymerase
• lactose utilisation
• mRNA
• protein
• lactose
• inactive repressor
• enzyme for lactose utilisation

Question 14

What do structural genes do?

Answer 14

Code for proteins

Question 15

What does the regulatory gene do?

Answer 15

Codes for transcription factor

Question 16

What do the control elements (promotor, operator) do?

Answer 16

Promotor - RNA polymerase binds to it
Operator - transcription factor binds to

Question 17

How does the Lac Operon control protein production?

Answer 17

Changes shape of repressor so doesn’t bind to the operator

Question 18

What are transcription factors?

Answer 18

• proteins that will bind to DNA and move in from cytoplasm
• attach RNA polymerase to DNA
• most are in an inactive form and activated by hormones
• some only in certain cell types
• some only present at particular stages of development

Question 19

What does posttranscriptional level mean?

Answer 19

Editing of mRNA

Question 20

What is an intron?

Answer 20

Section of gene that doesn’t code for an amino acid

Question 21

What is an exon?

Answer 21

Does the code for amino acids

Question 22

What is splicing?

Answer 22

Introns are removed when gene is transcribed, functional exons are joined together, causes introns to form a loop shape

Question 23

What happens during splicing?

Answer 23

• intron removed and form a loop shape due to spliceosomes
• only exons are left and spliced together
• mRNA may leave nucleus into cytoplasm for next stage of protein synthesis

Question 24

What are snRNP’s?

Answer 24

Small nuclear ribonucleoproteins

Question 25

What are homeobox sequences?

Answer 25

- highly conserved regions of DNA - all organisms have them, apart from bacteria - 180 base pairs

Question 25

What are hox genes?

Answer 25

- class of homeobox genes in animals to position body parts - hox genes have homeobox genes that code for homeodomains - every hox gene is a homeobox gene, but not every homeobox gene is a hox gene

Question 25

What are homeodomain proteins?

Answer 25

- hox genes have homeobox genes that code for homeodomains -transcription factors to activate/repress genes that regulate mitosis, apoptosis and cell cycle

Question 26

What is apoptosis?

Answer 26

- programmed cell death in development - series of biochemical events leader to an orderly and tidy death

Question 27

Why should the rate of cells dying balance the rate of cells produced by mitosis?

Answer 27

- not enough apoptosis leads to tumors forming - too much apoptosis leads to cell loss and degeneration

Question 28

How is apoptosis controlled?

Answer 28

- hox genes regulate mitosis and apoptosis - expression of these genes is regulated by stimuli and different stresses

Question 29

What are some internal controls of apoptosis?

Answer 29

- damage to DNA detected in cell cycle - genes are expressed that cause cell to pause/triggers apoptosis - release of hormones - physiological stress

Question 30

What are some external controls of apoptosis?

Answer 30

- change in light intensity, temp - pathogen attack - lack of nutrients - drugs can also have effect

Question 31

What is the process of apoptosis?

Answer 31

- normal cell - cell begins to bleb at the start of apoptosis, nucleus and cytoskeleton starts to disintegrate - cell fragments produced with intact plasma membranes and containing organelles - cell fragments are ingested and digested by phagocytic cells

Question 32

What are the stages of interphase?

Answer 32

- G1 - G1 checkpoint - S - G0 - G2 - G2 checkpoint - M checkpoint

Question 32

What are the stages of the cell cycle?

Answer 32

- interphase - nuclear division - cytoplasmic division

Question 33

What happens in G1?

Answer 33

- cell increases in size - proteins are synthesised - organelles divide and replicate - DNA damage is checked for damage at the checkpoint

Question 34

What happens in G2?

Answer 34

- increases in size - energy stores grow - checkpoint checks for errors

Question 35

What happens in S stage?

Answer 35

- synthesis of DNA

Question 35

What happens in G0?

Answer 35

- errors are picked up - leave cell and undergo differentiation

Question 36

What happens in M checkpoint?

Answer 36

- makes sure chromosomes are attached to spindle fibres - in metaphase