Modern Genetics

Question 1

What is a genome?

Answer 1

All of an organism’s DNA

Question 2

What are transcription factors?

Answer 2

Proteins which bind to DNA.

They bind to specific base sequences

Question 3

What are promoter sequences?

Answer 3

Found upstream of the gene they act on

Enable the binding of RNA polymerase and therefore promote transcription

Question 4

What are enhancer sequences?

Answer 4

Regulate DNA activity by changing chromatin structure (make it more or less open to RNA polymerase)
Open = active gene expression | Closed = gene inactivity - transcription factors either stimulate or prevent transcription of the gene

Question 5

What is DNA methylation?

Answer 5

Addition of a methyl group to CpG on DNA

Prevents transcription and affects histone structure to make more/less DNA accessible to RNA polymerase

Question 6

What is RNA splicing?

Answer 6

Post-transcriptional modification of mRNA

RNA splicing explains how eukaryotes produce more proteins than they have genes

Question 7

Describe the process of RNA splicing.

Answer 7

Gene is transcribed which results in pre-mRNA
All introns and some exons are removed
Remaining genes are joined by spliceosomes

Question 8

What can gene expression be changed by?

Answer 8

Epigenetic modification

; non-coding RNA, histone modification and DNA methylation

Question 9

What is the importance of epigenetic modification?

Answer 9

To ensure cell differentiation

Question 10

Define epigenetics.

Answer 10

Heritable and reversible modifications to the DNA that do not involve changes to the nucleotide sequence

Question 11

Describe the first part of histone modification.

Answer 11

Acetylation - addition of an acetyl group which activates chromatin and allows transcription

Question 12

Describe the second part of histone modification.

Answer 12

Methylation - addition of a methyl group, causes activation/inactivation of chromatin based on position of the lysine

Question 13

How does RNA splicing result in different products from a single gene?

Answer 13

The same exons can be joined a variety of ways to produce several different versions of mature functional RNA.

Question 14

What are stem cells?

Answer 14

Undifferentiated cells which have the ability to differentiate into many different cell types

Question 15

What are the different types of stem cells?

Answer 15

Multipotent
Pluripotent
Totipotent

Question 16

What are multipotent cells?

Answer 16

Cells which can give rise to multiple types of cells

Question 17

What are pluripotent cells?

Answer 17

Cells which can give rise to many types of specialised cells but NOT placental cells

Question 18

What are totipotent cells?

Answer 18

Cells which can give rise to all types of specialised cells INCLUDING placental cells

Question 19

Where are totipotent cells found?

Answer 19

For a limited time in a mammalian zygote

Question 20

Where are pluripotent, multi potent and uni potent cells found?

Answer 20

Mature (somatic) mammals

Question 21

What are pluripotent cells used for?

Answer 21

Treating human disorders by replacing damaged tissue

Question 22

What are some examples of stem cells?

Answer 22

Embryonic stem cells, adult stem cells, fused cells

Question 23

What are the benefits for stem cells?

Answer 23

Save many lives

Improve quality of life

Question 24

What are the ethical issues with stem cells?

Answer 24

Embryos are killed in the process of stem cell extraction
Risk of infection when cells are transplanted
They could become cancerous

Question 25

What are induced pluripotent stem cells?

Answer 25

Adult stem cells that have been reprogrammed to become pluripotent again

Question 26

Describe the formation of induced pluripotent stem cells

Answer 26

Fibroblasts taken from skin samples Viruses introduce 4 genes for transcription factors Cells behave like embryonic stem cells

Question 27

How can recombinant DNA be produced?

Answer 27

Isolation of gene Complementary sticky ends Recombinant DNA Reincorporate plasmid

Question 28

Give examples of vectors.

Answer 28

Gene guns Viruses Liposome wrapping Micro injection

Question 29

How do effective vectors behave?

Answer 29

Target right cells Incorporate gene into host genome Have no adverse side effects

Question 30

What do marker genes do?

Answer 30

Used to show where a foreign gene has been inserted

Question 31

How are marker genes used to identify recombinant cells?

Answer 31

Bacteria are transferred from a ‘master plate’ onto plates with antibiotics using sterile block If they don’t grow, gene was inserted successfully and colonies are still on the ‘master plate’

Question 32

What are marker genes?

Answer 32

Fluorescence and antibiotic resistance combined with replica plating

Question 33

What are transgenic plants?

Answer 33

Plants which contain genetic material from an unrelated organism

Question 34

What are the benefits of genetic modification?

Answer 34

Herbicide resistance Increased yield Increased nutrient value

Question 35

Gives examples of GM plants and their benefits.

Answer 35

Soya beans - linoleic acid (polyunsaturated) is replaced by oleic acid (monounsaturated) which oxidises less easily so doesn’t go off as fast - healthier

Question 36

How can PCR samples be used to predict amino acid sequence?

Answer 36

Using gene sequencing | This determines possible links to genetically determined conditions