control of gene expression

Question 1

how are cells able to control their metabolic activities

Answer 1

by regulating transcription + translation of a gene

Question 2

define mutation

Answer 2

any change in amount or structure

of DNA of an organism

Question 3

how do mutations occur

Answer 3

spontaneously during DNA replication

Question 4

how can mutations be passed on

Answer 4

if the mutation occurs in the gametes

Question 5

what are the different types of gene mutation

Answer 5

addition, deletion, substitution, inversion, duplication and translocation of bases.

Question 6

how is the mutation rate increased

Answer 6

using mutagenic agents, such as carcinogens

Question 7

what can mutations result in

Answer 7

change in amino acid sequence of the polypeptide

which changes the primary structure, then the secondary then the 3D tertiary structure of the protein

Question 8

why do some mutations not change the amino acid

Answer 8

due to the degenerate nature of the genetic code

more than one triplet can code for the same amino acid

Question 9

what can base additiondo

Answer 9

cause a frame shift to the right

Question 10

what is a base deletion called

Answer 10

point mutation

Question 11

what is the inversion of bases

Answer 11

DNA breaks off + reinserted at same position

but is now inverted

Question 12

what is translocation + its consequences

Answer 12

group of bases break off
+ get reinserted on another chromosome

can also cause cancer + reduced fertility

Question 13

what is totipotency

Answer 13

ability of embryonic stem cells to divide into any type of cell

Question 14

totipotent cells ; where, what

Answer 14

occur for only a limited time in early mammalian embryo
can divide into any type of body cell

can be used to treat disease

Question 15

what causes cell differentiation

Answer 15

during development, totipotent cells translate only part of their DNA

Question 16

pluripotent; where, what

Answer 16

found in embryos, in blastocyst

can divide into almost any type of cell except placenta cell

Question 17

multipotent; where, what

Answer 17

mature mammals

can divide to form a limited no of cell types

Question 18

unipotent; where, what

Answer 18

mature mammals, made in adult tissue

can only differentiate into a single type of cell

Question 19

what are iPS (induced pluripotent stem) cells for and how are they produced

Answer 19

can be produced from adult somatic cells using appropriate protein transcription factors

Question 20

how can a gene be expressed

Answer 20

transcription the gene can be stimulated
when specific transcriptional factors move
from cytoplasm into nucleus

Question 21

structure of a transcription factor

Answer 21

has a DNA binding site

and a receptor

Question 22

how does the transcription factor stimulate transcription

Answer 22

transcription factor binds to DNA
at DNA binding site which is specific to a certain gene
to the correct, complementary gene

Question 23

what happens when the gene isn’t being expressed

Answer 23

inhibitor molecule binds to transcriptional factor at
DNA binding site
blocking it, preventing it from binding to DNA + starting transcription

Question 24

explain and describe the role of oestrogen in gene expression

Answer 24

can influence transcriptional factors

• diffuses across membrane as its lipid soluble
• combines with transcriptional factor at receptor site
• hormone changes shape of transcriptional factor causing inhibitor molecule to be released
• so DNA binding site is exposed, factor can go into nucleus + bind to DNA

Question 25

what is epigenetics

Answer 25

heritable changes in gene function

without changes to base sequence of DNA

Question 26

what causes these heritable changes

Answer 26

changes in the environment by inhibiting transcription

Question 27

how do changes in the environment inhibit transcription

Answer 27

increased methylation of DNA
or
decreased acetylation of associated histones