Mutations and Gene Expression

Question 1

define stem cells?

Answer 1

cells that can divide and differentiate to become diff types of cell

Question 2

totipotent stem cells

Answer 2

can divide and differentiate into any type of specialised cell

• very early mammalian embryos
• can form placenta cells

Question 3

pluripotent stem cells

Answer 3

can differentiate into MANY types of specialised cell

• embryo and adult cells
• cant make placenta cells

Question 4

multipotent stem cells

Answer 4

can differentiate into FEW types of specialised cell

Question 5

unipotent stem cells

Answer 5

can differentiate into ONE type of specialised cell

Question 6

what can a change in the internal enviro do?

Answer 6

affect expression of genes

cells = specialised (cant be reversed)

Question 7

conditions within cells control what?

Answer 7

which genes expressed (transcribed and translated)

into proteins

Question 8

what does RNAi do?

Answer 8

control gene expression by preventing translation

Question 9

what is siRNA?

Answer 9

• small interfering RNA
• short stranded RNA
• combines with proteins to = siRNA-protein complex

Question 10

what does siRNA do?

Answer 10

• siRNA = single stranded
• has complementary base sequence to target mRNA
• siRNA-protein complex breaks down mRNA into pieces
• prevents translation
• mRNA pieces recycled

Question 11

what does microRNA do?

Answer 11

• combines with protein = microRNA-protein complex
• binds to mRNA by comp base pairing
• less specific than siRNA - works on more than one mRNA
• prevents translation - prevents ribosome attaching
• mRNA stored / recycled

Question 12

what are transcription factors

Answer 12

proteins that control the rate of protein synthesis by switching some genes on and other genes off

Question 13

what are promoter regions

Answer 13

short sequence of DNA at start of gene

Question 14

how transcription factors work?

Answer 14

• TF move from cytoplasm to nucleus
• binds to promoter region
• activators - help RNA polymerase bind to gene (TRANSCRIBED)
• repressors - prevent RNA polymerase binding to gene (NOT TRANSCRIBED)

Question 15

what can transcription factors also be turned on / off by?

Answer 15

second messenger

cAMP

Question 16

controlling TF

oestrogen example

Answer 16

• oestrogen = steroid hormone
• binds to receptor called oestrogen complex
• forms oestrogen-oestrogen complex

Question 17

define epigenetics?

Answer 17

changes to gene expression caused by enviro factors ( without changing base sequence of DNA)

Question 18

what does epigenetics do?

Answer 18

• controls gene expression by preventing transcription
• can be inherited between gen
• helps organisms respond to changes in enviro

Question 19

More Methylation =

Answer 19

Terminates Transcription

Question 20

what are CpG sites

Answer 20

where C and G next to each other in DNA

Question 21

what do methylated CpG sites prevent?

Answer 21

transcription enzymes attaching (RNA polym)

transcription prevented

Question 22

less acetylation of histones =

Answer 22

Terminates Transcription

Question 23

what are histones

Answer 23

proteins that supercoil DNA into chromatin

Question 24

what does acetylation do?

Answer 24

• acetyl groups make histones space out
• allows transcriptional enzymes (RNA polym) attach
• gene expressed
• enzymes remove acetyl groups
• prevent transcription

Question 25

bone marrow transplant

Answer 25

- contains multipotent stem cells - can differentiate into RBC and WBC - replace faulty bone marrow with new bone marrow = forms new healthy cells

Question 26

growing new organs

Answer 26

- no donor needed - induced pluripotent stem cells - iPS have same antibodies - no organ rejection

Question 27

advantages of growing new organs and transplants

Answer 27

- saves lives - improves quality of life - prevents suffering

Question 28

ethical issues to growing new organs and transplants

Answer 28

- stem cells taken from IVF embroys which could develop into embryos if implanted - from fertilisation zygote has right to life (as you use unfertilised eggs which are triggered to divide) - adult stem cells not pluripotent iPS may be future sol

Question 29

what can transcription be controlled by

Answer 29

methylation

Question 30

hypermethylation

Answer 30

- TSG - protein not transcribed - uncontrolled cell division

Question 31

hypomethylation

Answer 31

- proto-oncogenes - more proteins transcribed - uncontrolled cell division

Question 32

describe benign tumours

Answer 32

- non-cancerous - grow slowly - harmless - can become malignant

Question 33

describe malignant tumours

Answer 33

- grow quickly - destroy tissue - can break up and spread to blood / lymphatic system

Question 34

describe what tumour cells look like

Answer 34

- mitosis - more cells dividing - nuclei - large and odd shaped - more than 1 - cell shape = irregular - function - loss of normal function - arrangement - disorganised

Question 35

how can high levels of oestrogen cause some types of breast cancer

Answer 35

- binds to proteins = transcription factor - called oestrogen-oestrogen receptor complex - increases rate of cell division - inc rate of dna rep - inc chance of mutations - inc chance of cancer

Question 36

define mutation

Answer 36

change to base sequence of DNA

Question 37

no change to amino acid sequence

Answer 37

- amino acid coded for by more than triplet - DNA = degenerate

Question 38

change to single amino acid

Answer 38

- changes one DNA triplet - changes translation of amino acid - changes primary structure - changes hydrogen/ionic bonding - changes tertiary structure of protein

Question 39

change to many sequence of amino acids

Answer 39

- frame shift changes sequence of all following dna triplets - changes all following amino acid sequence - changes primary structure - changes hydrogen/ionic bonding - changes tertiary structure

Question 40

mutations that change sequence of DNA

Answer 40

- addition - duplication - deletion

Question 41

define induced pluripotent stem cells

Answer 41

treating unipotent stem cells with transcription factors that make them pluripotent

Question 42

iPS

Answer 42

- use modified virus as vector - virus inserts TF genes from pluripotent stem cells into DNA of unipotent stem cells - TF expressed - make totipotent stem cells this way

Question 43

embryonic stem cells

Answer 43

- embryos made in lab by IVF - pluripotent stem cells removed after few days - embryo destroyed - pluripotent stem cells differentiate into all types of body cells

Question 44

adult stem cells

Answer 44

- taken from adults in operation - adult stem cells = multipotent - less useful for medicine as cant form every type of cell

Question 45

how do mutations occur

Answer 45

spontaneous mistakes during dna rep

Question 46

what do mutagenic agents do

Answer 46

increase rate of mutations

Question 47

base analogs

Answer 47

chemical that can substitute for normal nucleotide base SUBSTITUTION MUTATION

Question 48

radiation

Answer 48

change structure of dna UV, IONISING

Question 49

change dna bases

Answer 49

chemicals that react with dna to change its structure SUB / DELETION

Question 50

define substitution

Answer 50

one base swapped for another | (no change, dna = degenerate)

Question 51

define addition

Answer 51

extra base added

Question 52

define deletion

Answer 52

base removed - causes frame shift - all following triplets in sequence affected

Question 53

define inversion

Answer 53

sequence of bases reversed - no change - change few AA - no frame shift

Question 54

define duplication

Answer 54

one / more bases repeated

Question 55

define translocation

Answer 55

sequence of DNA moved from one part of genome to another part of genome (in same chromosome / to diff chromosome)