D1.3 Mutations in genes

Question 1

Function of non-coding sequences in genes (4)

Answer 1

regulators of gene expression

introns : found in eukaryotes, removed after transcription

telomeres : found at ends of chromosomes to ensure correct replication

genes for tRNA and rRNA

Question 2

Define a mutagen

Answer 2

chemical or physical agent which can cause a mutation

Question 3

Define a mutation (2)

Answer 3

changes to genetic composition of cell

change in order of bases in DNA strand

Question 4

2 regions of pre-mRNA (2)

Answer 4

exons : protein coding regions

introns : non-protein coding regions

Question 5

region of mRNA

Answer 5

exons : protein regions

Question 6

Define post-transcriptional modification (2)

Answer 6

process where mRNA which is produced needs to be modified before translation

introns are removed using spliceosomes

Question 7

Define spliceosomes

Answer 7

large enzymes found in nucleus

Question 8

Define spontaneous mutation

Answer 8

mistake made when DNA is copied during production of gametes

Question 9

3 Different types of mutation (3)

Answer 9

Substitution

Insertion

Deletion

Question 10

Features of single nucleotide polymorphisms (2)

Answer 10

occur when one nucleotide is replaced by another nucleotide in DNA sequence

effect on protein structure depends on whether substitution is synonymous or non-synonymous

Question 11

Define synonymous SNPs (3)

Answer 11

known as neutral/same-sense mutations

change one codon of amino acid into another codon of same amino acid

do not affect phenotype

Question 12

Define non-synonymous SNPs (3)

Answer 12

change in amino acid sequence causes change in protein function

non-sense - changes codon into stop codon, polypeptide is not complete + resulting protein does not function properly

mis-sense = change codon into codon coding for different amino acid

Question 13

Causes of frameshift mutations (3)

Answer 13

insertion

deletion

duplication

Question 14

Impacts of frameshift mutations (3)

Answer 14

alters amino acid sequence coded by DNA sequence

addition of new nucleotides alters grouping of codons

mRNA transcript produced will have different codon structures

Question 15

Define insertion for gene mutation

Answer 15

one or more nucleotides added to DNA sequence

Question 16

Define deletion for gene mutation

Answer 16

one or more nucleotides are removed from DNA sequence

Question 17

Examples of chemical mutagens (3)

Answer 17

mustard gas

nitrous acid

Formaldehyde

Question 18

Example of physical agent mutagens (3)

Answer 18

UV Radiation

X-Ray

Gamma rays

Question 19

Impact of radiation on gene structure (3)

Answer 19

single-strand breaks - interrupts continuity of template strand –> replication errors

double strand breaks

chemical alterations to bases

Question 20

Base with highest probability of mutation (3)

Answer 20

cytosine

can experience chemical reaction called deamination

can lose an amine group –> becomes uracil

Question 21

Factors that influence mutation rate (3)

Answer 21

exposure to mutagens

DNA repair mechanisms

fidelity of DNA replication - accuracy of DNA copy

Question 22

Where can gene mutations occur (2)

Answer 22

somatic cells - all cells in body except germ cells

germ cells - cells that give rise to eggs + sperms

Question 23

Mutations in somatic cells (2)

Answer 23

can cause diseases in person’s lifetime (e.g cancer)

not passed onto offspring

Question 24

Mutations in germ cells (2)

Answer 24

passed onto offspring - mutations inherited by offspring

can cause genetic disorders, change chromosome number, increase susceptibility to certain disease

Question 25

Define neutral/silent mutations (3)

Answer 25

mutations which do not significantly affect organism neutral mutations - occur in non-coding regions of genome + regions that do not alter function of essential genes silent mutations - occur in coding regions but do not alter amino acid sequence due to degeneracy

Question 26

Define harmful mutations (2)

Answer 26

mutations that cause negative consequences for organism can cause disease, abnormality, reduce organisms survival

Question 27

Define beneficial mutations (2)

Answer 27

mutations that are advantageous to organism improve ability to adapt, reproductive success, resistance to disease

Question 28

Define genetic engineering (2)

Answer 28

process of altering DNA of organisms to introduce new characteristics, modify characterstics, remove undesired characteristics

Question 29

Define gene knockout technique (2)

Answer 29

specific gene is intentionally removed/changed to prevent its expression helps to discover function of specific gene

Question 30

Gene knockout technique in mice (4)

Answer 30

prepared DNA inserted into genome of embryotic mouse cells --> replaces + deletes target gene succesful procedures grown into adult mice males + females with only one copy mated - 25% expected to have no copies of target gene (knockout mice) phenotype of knockout mice investigated to find out traits changed

Question 31

Components of CRISPR-Cas 9 (2)

Answer 31

enzyme Cas9 - cuts DNA at specific target sites on chromosome CRISPR

Question 32

Define CRISPR (2)

Answer 32

short repeated base sequences unique spacer sequences

Question 33

Define the CRISPR Cas-9 system for bacteria (3)

Answer 33

used by bacteria against invading foreign DNA (viruses) incorporate short segments of foreign DNA into their own genome bacteria create molecular record of previous infections

Question 34

Explain the CRISPR Cas-9 procedure for bacteria (4)

Answer 34

foreign DNA matches foreign DNA matches CRISPR spacer --> corresponding RNA identifies + binds to specific viral sequences guides Cas9 to target DNA to make precise cuts in DNA causes double stranded break that can be repaired by cell's DNA repair mechanism

Question 35

CRISPR Cas-9 in gene editing (4)

Answer 35

creating single guide RNAs (sgRNA) to target specific genes for modification or deletion sgRNA molecule specifically targets + bind to a particular DNA sequence of interest guides Cas9 enzyme to location and enables it to make precise cuts in the DNA, resulting in double-strand break. scientists can add, delete or modify the DNA sequences at that point

Question 36

Application of CRISPR Cas-9 system (4)

Answer 36

gene therapy agriculture disease modelling genetic engineering of microorganisms

Question 37

Gene therapy in CRISPR Cas-9 system (3)

Answer 37

treats genetic disorders correcting disease-causing mutations in a patient’s cells e.g sickle cell anaemia.

Question 38

Agriculture in CRISPR Cas-9 system (3)

Answer 38

ability to transform crop breeding practices introducing precise genetic modifications to enhance desirable traits improve crop yield + nutritional content and disease resistance

Question 39

Disease modelling in CRISPR Cas-9 system (3)

Answer 39

creates animal models to simulate human diseases introduces mutations or deleting genes in animals researchers gain info into disease progression + potential treatment

Question 40

Genetic engineering of microorganisms (3)

Answer 40

make modifications to genetic material of bacteria, yeast or other microorganisms. enhance microorganisms' ability to produce valuable compounds such as pharmaceuticals, biofuels and enzymes. creation of efficient microbial factories to contribute to sustainable production

Question 41

Define conserved sequences

Answer 41

sequences remain identical or similar across species or group of species

Question 42

Define highly conserved sequences

Answer 42

sequences that remain similar over long periods of evolution

Question 43

Role of conserved and highly conserved sequences (2)

Answer 43

provide clues about function/importance sequences for evolution of species functional constraints - selective pressures prevent mutations in these genes as they are vital for life