gene expression

Question 1

name the 3 compnents of a nucleotide

Answer 1

• phosphate group
• deoxyribose
• nitrogenous base

Question 2

what is transcription?

Answer 2

the formation of pre mrna with a complementary sequence of bases to the dna , occurs in the nucleus

Question 3

what is the process of splicing?

Answer 3

removing non coding introns and leave only the coding exons

Question 4

what bases are found in DNA?

Answer 4

A,T,C,G

Question 5

what bases are found in mRNA?

Answer 5

A,U,C,G

Question 6

where is DNSA found?

Answer 6

in the nucleus

Question 7

where is mRNA found?

Answer 7

in the cytoplasm

Question 8

describe the process involved in stimulation of gene transcription

Answer 8

• each transcription factor has a site that bind to a specific base sequence of the DNA in the nucleus
• binding og the transcriptional factor to thew promoter region allows the attatchment of RNA polymerase to the dna and transcription is stimulated
• messenger rna is produced and the genetic code it carries is then translated into a polypeptide

Question 9

define the promoter region

Answer 9

the site of a transcriptional factor that binds to a specific base sequence in the nucleus

Question 10

describe oestrogen

Answer 10

lipid soluble
steroid hormone
transported in the blood stream

Question 11

describe how oestrogen can bind

Answer 11

like a substrate and an enzyme

they have complemetary shape

Question 12

how does oestrogen initiate transcription?

Answer 12

• combines with receptor site on transcription factor
• this removes an inhibitor molecule that normally blocks the DNA binding site
• allowing the transcriptional factors to bind to the DNA promoter region

Question 13

what does RNAi stand for?

Answer 13

small interfering RNA

Question 14

define RNA interference

Answer 14

the inhibition of gene expression at the translation stage

Question 15

suggest why RNA interference is important in a cell

Answer 15

• linit or stop the production of a specific protein potentially
• to prevent mRNA containing a mutation from being translated
• to prevent mRNA from a virus being translated

Question 16

what makes RNAi?

Answer 16

special regulatory genes

Question 17

what cuts mRNA in two?

Answer 17

RNAi binding to specidic mRNA molecules with a complementary base sequence by complementary base pairing

Question 18

when mRNA is cut in two , what does that mean?

Answer 18

mRNA can no longer be translated so protein synthesis stops

Question 19

what are the two main functions of stem cells?

Answer 19

• they are undifferentiated but can differentiate into specialised cells
• they can replace themselves

Question 20

name the 4 types of stem cells

Answer 20

• totipotent
• pluripotent
• multipotent
• unipotent

Question 21

describe the difference between pluripotent and unipotent

Answer 21

pluripotent cells can differentiate into almost alll cells of the adult body (except placental cells) while unipotent stem cells can only form a single type of cell in the adult body

Question 22

describe totipotent cells

Answer 22

cells that can divdie to produce any cell in the body

-in mamals they are found in embryos

Question 23

describe pluripotent cells

Answer 23

cells that can divide in unlimited numbers and can differentiate into almost any specialised cell
-in mammals they are found in the embriys

Question 24

describe multipotent cells

Answer 24

cells that can divide to form only a limited number of different cell types
- foudn in mature mammals

Question 25

describe unipotent cells

Answer 25

have the lowest differential potential, only one type of cell or tissue -found in mature mammals

Question 26

why are stem cells good for treating human disorders

Answer 26

they can be extracted and then grown in culture in the labatory and then used to replace damaged cells or tissues in a patient

Question 27

other than ethical issues, give an advantage of using multipotent rather than embryonic stem cells for this process

Answer 27

no transplant rejection if stem cells is obtained from patients own tissue

Question 28

other than ethical issues, give an disadvantage of using multipotent rather than embryonic stem cells for this process

Answer 28

the stem cells can only develop into a limited number of cell types, depending on which tissue they were obtained from.

Question 29

give a defintion for the term methylation

Answer 29

methylation is the addition of a methyl group to a molecule

Question 30

who does increased methylation inhibit transcription?

Answer 30

-preventing transcription factors from binding to the DNA -attracting proteins that decrease acetylation of histones therefore resulting in condensation of the chromatin. genes become inaccessible to transcription factors

Question 31

summarise the effects of acetylalation of methylation on transcription

Answer 31

acetylation activates transcription | methylation messes with transcription