Eukaryotes And Prokaryotes

Question 1

How many genes do prokaryotes have

Answer 1

500 to 4000

Question 2

How many genes do eukaryotes have

Answer 2

6000 to 30,000

Question 3

True or false: Prokaryotes have Introns (non-codon regions)

Answer 3

False, eukaryotes do

Question 4

What are the components of a chromatid (chromosome)

Answer 4

Chromatin (DNA strands) wrapped around histomes, (8) clustered into a nucleosome, nucleosides fold into coils, coil further and further to make the chromatid of a chromosome

Question 5

What is chromatin

Answer 5

Combination of DNA, RNA and proteins that make up eukaryotic chromosomes

Question 6

What is euchromatin

Answer 6

Lightly asked form of chromatin rich in gene conc. usually actively being expressed, loosely packed to allow RNA in to transcribe

Question 7

What is heterochromatin

Answer 7

Tightly packed form of DNA, little or no expression. RNA can’t access it because it’s too tight

Question 8

Why do the number of proteins coded for far exceed the number of genes we have

Answer 8

Because introns can be cut out and different exons can be spliced together, alternative splicing

Question 9

What is epigenetics

Answer 9

Wheh environmental factors change genotype or expression, can be inherited

Question 10

What is DNA transcription

Answer 10

DNA-directed synthesis of RNA

Question 11

What aids mRNA I’m getting from nucleus to ribosome

Answer 11

The addition of a 5’ cap (prevents premature breakdown) and a Poly-A tail (helps with transport out of nucleus)

Question 12

Describe the initiation of RNA polymerase

Answer 12

Polymerase binds to Promoter, DNA strand unwinds and enzyme initiates RNA synthesis at start point on template strand

Question 13

Describe the elongation step of RNA polymerisation

Answer 13

Polymerase runs DOWNstream, unwinding and elongating RNA transcript 5’ to 3’.

Question 14

Describe termination of RNA Polymerase

Answer 14

Eventually polymerase transcribes terminator sequence which signals end of transcription unit. RNA transcription released and polymerase detaches from DNA

Question 15

What processes do eukaryotic genes have to go through that prokaryotic genes don’t

Answer 15

RNA Splicing
RNA capping (5’ capping) 
Poly-A tail (3’ Polyadenylation)
exporting 
miRNA Gene silencing

Question 16

What are snRNAs and Spliceosomes

Answer 16

snRNAs and proteins come together into a spliceosome. SnRNAs then base pair with nucleotides at the end of the introns. RNA transcriptase then cuts to release introns and the Exon’s are spliced back together and released from spliceosome.

Question 17

What is an operon

Answer 17

Clustered genes in a prokaryote (functionally related)

Question 18

What is a repressive protein

Answer 18

Protein activated by specific molecule, then binds to operator and blocks transcription (prokaryote)

Question 19

What is the de-repression of transcription

Answer 19

Molecules bind to depressor and lower DNA binding cap

Question 20

What is “Activation possible” gene control in prokaryotes

Answer 20

When proteins bind to promoter and stimulate RNA polymerase binding

Question 21

How long is a poly-A tail

Answer 21

50-250 base pairs long

Question 22

What is the TATA box

Answer 22

T & A bases ~25bp long in promoter region, transcription factor bonds to it and helps RNA polymerase II find and attach to the DNA strand

Question 23

True or false: RNA synthesis is done by a transcription factor complex rather than just RNA Polymerase

Answer 23

True, RNA polymerase (II), transcription factor, enhancer, activated DNA binding proteins

Question 24

Describe what a phosphorylated protein does in the nucleus

Answer 24

Addition of phosphate to protein, activated enzyme enters through nuclear pore and interacts with TFs. TFs modified (activated) and binds to enhancer region and moves to interact with the rest of the transcription protein. When complex is complete, transcription starts

Question 25

How do chromatin modifications affect gene expression

Answer 25

Affect availability of genes for transcription

Question 26

What is the affect of DNA methylation in humans

Answer 26

Causes DNA to be tightly packed, not allowing mRNA in and causes genes to long term remain unexpressed

Question 27

How does Histone acetylation affect gene expression

Answer 27

When his tones are acetylated, they grip DNA less tightly giving easier access of genes in that region