Gene expression

Question 1

Inversion mutation

Answer 1

short sequence of nucleotides detach and rejoin the wrong way around

Question 2

Duplication mutation

Answer 2

nucleotide is repeated causing frame shift to right

Question 3

Translocation mutation

Answer 3

short section of nucleotides detaches + reinserted on a different gene (possibly chromosome), significantly impact gen expression -> phenotype

Question 4

Key properties of stem cells

Answer 4

Self-renewal (divided whilst remaining undifferentiated), potency (can diferentiate)

Question 5

Name 4 types of stem cells

Answer 5

Totipotent: early embryo, into any cell (limited time)

Pluripotent: fetal, almost any type of cell (not placenta)

Multipotent: adult/umbilical blood, limited no. of cells

Unipotent: derived from multipotent/adult tissue, one type of cell

Question 6

Induced pluripotent stem cells

Answer 6

Unipotent stem cells genetically altered to have characteristics of pluripotent s. cells/embryonic stage
- induce genes + transcriptional factors in cell to express themselves

capable of self-renewal, could replace embryonic stem cells in research (overcome ethical issue)

Question 7

Role of transcriptional factor

Answer 7

Binds to specific base sequence of DNA in nucleus, begins transcription of this sequence -> expressing gene

Question 8

Effect of oestrogen on transcription

Answer 8

• Oes. lipid soluble so diffuses across cell membrane
• binds to receptor site on TF as complementary
• shape of DNA binding site changes on TF
• TP diffuses into nucleus + binds w/ DNA beginning process of transcription

Question 9

Effect of siRNA on translation

Answer 9

• double stranded RNA is hydrolysed by enzyme into siRNA
• one of the two strands of single siRNA combines w/ enzyme
• siRNA strand pairs w/ complementary bases on mRNA strand
• enzyme cuts mRNA into smaller sections

Question 10

What is the epigenome?

Answer 10

multitude of compounds that can instruct the genome, flexible + so responds to env. changes activating or inhibiting genes

Question 11

Effect of methyl

Answer 11

Increase inhibits transcription

binds to cytosine base, attracts proteins that condense DNA histone complex so TF cannot bind

Question 12

Effect of acetyl

Answer 12

Decrease inhibits transcription

increasing + charge on histones which increases attraction of phosphate groups in DNA so stronger association (tighter)
-> TF cannot bind

Question 13

What are the two types of chromatin?

Answer 13

heterochromatin: tightly packed so inaccessible to promoters + enzymes

euchromatin: loosely packed so readily accessed by enzymes

Question 14

What is cancer?

Answer 14

Group of diseases caused by damage to genes regulating mitosis which can lead to a tumour

Question 15

How do primary tumours spread?

Answer 15

• early tumour enlarges + develops blood + lymphatic vessels
• tumour cells enter blood + lymphatic vessels
• circulating tumour cells adhere to blood vessel walls, squeeze through to form distant metastases
  OR
  metastasis in lymph node

Question 16

2 ways oncogene can cause excessive cell division

Answer 16

• receptor protein on cell surface overexpressed so permanently activated
• oncogene may code for growth factor which is produced excessively stimulating division
• hypomethylation

Question 17

How can tumour suppressor genes be involved in causing cancer?

Answer 17

hypermethylation in promoter region inhibits transcription so tumour suppressor gene switched off
-> inactivated so uncontrolled cell division

Question 18

Role of oestrogen in development of some breast cancers

Answer 18

post menopause fat cells of breast produce more oestrogen, tumour cells increase oest., w.b cells drawn in also increase oest

oest. activates gene by binding to a gene which promotes transcription

so can cause proto-oncogenes in breast cells to develop into oncogenes

Question 19

How many genes are in human genome?

Answer 19

20,000, over 3 billion base pairs

Question 20

What is WGS?

Answer 20

Whole Genome Shotgun
cutting DNA into smaller easily sequenced sections then using computer algorithm to align overlapping segments, assembling entire genome

*methods constantly being updated

Question 21

What is SNP and why is it important?

Answer 21

single nucleotide polymorphism, single base variations in genome that are associated w/ disease

allows quick identification of potential medical problems for early intervention, can est. evol. relationships

Question 22

Why is determining proteome of simpler organisms easier?

Answer 22

• prokaryotes don’t have introns so genome can directly sequence proteins derived from their genetic code
• most have just one piece of circular DNA not associated w/ histones

Question 23

Why might knowledge of a proteome pathogen help control disease it causes?

Answer 23

Helps identify antigens so that they can be used to create a vaccine which provides immunity