epigenetics

Question 1

what are transcription factors?

Answer 1

proteins

Question 2

where do transcription factors move from and to

Answer 2

move in from the cytoplasm into the nucleus

Question 3

where do transcription factors bind

Answer 3

promoter regions at the start of a gene/DNA

Question 4

what happens when transcription factors bind to dna

Answer 4

enable RNA polymerase to attach to the start of the gene and begin transcription

Question 5

what happens when a gene is not being expressed

Answer 5

the attachment sits on the transcription factor is unable to to bind to the promoter region

Question 6

what are activators?

Answer 6

transcription factors that help RNA polymerase bind to the DNA and activate transcription

Question 7

what are repressors?

Answer 7

transcription factors that decrease the rate of transcription by preventing the binding of RNA polymerase to DNA

Question 8

how are transcription factors important in the synthesis of proteins

Answer 8

• bind to the DNA at specific base sequences and can stimulate/prevent transcription by turning the gene on/off

Question 9

how does an activated oestrogen receptor affect a target cell

Answer 9

• diffuses into the nucleus and binds with a transcription factor so that it can bind to the promoter region of a gene
• this stimulates RNA polymerase which increases transcription

Question 10

what is siRNA

Answer 10

small interfering RNA

Question 11

what is RNAi

Answer 11

the process of siRNA cutting up mRNA

Question 12

what are the 2 types of RNA

Answer 12

• siRNA

* miRNA

Question 13

explain the whole process of RNAi

Answer 13

1) a double stranded RNA is hydrolysed into siRNA
2) the siRNA becomes separated into single strands which then associated with enzymes/proteins
3) single strand of siRNA will complementary bind to mRNA
4) associates enzymes will cut mRNA into fragments and consequently no transcription happens(/no protein formed)

Question 14

how is oestrogen an activator/how does it increase transcription

Answer 14

• diffuses through the plasma membrane of cells through the cytoplasm and into the nucleus
• binds to a complementary oestrogen receptor (transcription factor)
• this binding changes the shape of the oestrogen receptor forming an oestrogen-receptor complex
• this complex can now bind to the promoter region of a gene
• consequently acting as an activator, RNA polymerase binds and transcription begins

Question 15

what are the 5 types of stem cells

Answer 15

totipotent, pluripotent, induced pluripotent, multipotent, unipotent

Question 16

source and characteristic of totipotent stem cells

Answer 16

SOURCE:

• fertilised egg
• zygot

CHARACTERISTICS:
- can mature into any body cell