Unit 3 Chapter 18: Gene Regulation + Expression in Eukaryotes

Question 1

Which two types of DNA elements that control transcription are unique to eukaryotes

Answer 1

• enhancers

- silencers

Question 2

What distinguishes enhancers and silencers from promoter elements

Answer 2

1. can act at large distances

2. can act in either orientation

Question 3

What do enhancers do

Answer 3

bind activators

• can be more than 100, 000 bps away from promoter
• can be located inside introns or in untranscribed sequence either in the 5’ or 3’ side of the gene
• unique to eukarykotes

Question 4

What do silencers do

Answer 4

bind repressors

• unique to eukaryotes
• stop transcription

Question 5

What determines which proteins are synthesized in what tissues

Answer 5

enhancer and silencer-binding transcription factors

Question 6

What is special about Heat shock genes and eukaryotic genes

Answer 6

each gene having its own promoter/enhancer/silencer combination (like all eukaryotic genes) and euks can mix and match their components for uniq expression

Question 7

What is heterochromatic

Answer 7

super tightly wound DNA and stains darkly

-not transcribed in contrast to euromatin

Question 8

What is euromatin

Answer 8

stains lightly

Question 9

How do females deal with having 2 X chromosomes

Answer 9

condensing it into a state that prevents transcription

- inactivated chromosome = a barr body

Question 10

How are calico cats calico cats (what trait makes them this way)

Answer 10

Calicos are always females that are heterozygous for an X-linked fur color gene; they have one yellow allele and one black allele. Depending on which X chromosome was inactivated in the cell giving rise to a patch of skin, that patch will be yellow (more orange actually) or black

Question 11

What is alternative splicing

Answer 11

Sometimes, when splicing the intron out of an RNA, an exon will be spliced out as well, creating a protein that is missing a chunk. The presence or absence of this chunk can affect how the protein functions

Question 12

Why are tetraploids bigger than diploids

Answer 12

their cells are bigger

Question 13

What is a genome

Answer 13

all of the hereditary info in an organism including not only genes but also other non gene stretches of DNA

Question 14

What is chromatin remodelling

Answer 14

occurs before transcription, the stretch of DNA containing the promoter is released from the chromatin so that RNA polymerase can bind to it

Question 15

Is DNA negatively or positively charged

Answer 15

negatively

Question 16

What are nucelosomes

Answer 16

DNA wrapped around histones

Question 17

What is the TATA bindning protein

Answer 17

TBP

-first step in transcription when promoter interacts with it

Question 18

What are regulatory sequences

Answer 18

sections of DNA (like 5’cap and 3’ tail) that are involved in on controlling activity of genes

Question 19

What are regulatory transcription factors

Answer 19

proteins that bind to enhancers, silencers or promoter proximal elements
-responsible for expression of genes in certain cell types and at certain stages of development

Question 20

What are basal transcription factors

Answer 20

interact with promoter and are not restricted to certain cell types
-must be present for transcription to occur but don’t regulate anything

Question 21

What is the mediator complex

Answer 21

does not bind to DNA, creates physical link between regulatory and basal transcription factors

Question 22

What is alternative splicing

Answer 22

splicing the same primary RNA transcript in different ways to produce different mature mRNAs and diff proteins
-allows a single gene to code for many products

Question 23

What is RNA interference

Answer 23

when the lifespan of mRNA is controlled by tiny single stranded RNAs that bind to complementary sequences in the mRNA which prevent it from being translated into a protein
-don’t want a perfect fit

Question 24

What are the 4 ways that gene expression differs in bacteria and eukaryotes

Answer 24

1. packaging (in euks DNA must be relaxed, default state is coiled)
2. alternative splicing (bacs have 1-1 ratio of gene to protein)
3. complexity
4. coordinated expression-operons in bact, rare in euks; regulatory transcription factors allow this in euks)

Question 25

In multi cellular euks, why are cells different

Answer 25

because they express diff. genes (not because they have diff genes)

Question 26

What is a tumour suppressor gene

Answer 26

a gene associated with tumour formation when its product does not function normally