Gene Structure and Function

Question 1

DNA (deoxyribonucleic acid)

Answer 1

stores genetic information, first nucleic acid in Central Dogma

Question 2

6 different types of RNA

Answer 2

mRNA, rRNA, tRNA, miRNA, siRNA, lncRNA

Question 3

mRNA

Answer 3

transcribed from DNA, undergoes processing before translation

Question 4

rRNA

Answer 4

ribosomal RNA that makes up the subunits of the ribosome

Question 5

tRNA

Answer 5

not discussed at length in class, but tRNA bring the amino acids to the ribosome for protein formation

Question 6

miRNA

Answer 6

clinical uses, “hot” topic of genetics currently due to potential tumor detection
short, only 20 bases long

Question 7

siRNA

Answer 7

helps to inhibit transcription

Question 8

lncRNA

Answer 8

long noncoding RNA

Question 9

Central Dogma

Answer 9

DNA—> RNA—>Protein

with transcription taking place between DNA and RNA and translation occurring from RNA to Protein

Question 10

What is an exception to the Central Dogma?

Answer 10

retroviruses

Question 11

What are some examples of retroviruses?

Answer 11

HIV, FIV, FELV, EIA

***No known retroviruses in canines

Question 12

What 4 elements make up a gene?

Answer 12

promoter, enhancer, exons, introns

Question 13

Promoter

Answer 13

start of transcription where RNA polymerase attaches, precedes the gene about to be transcribed

Question 14

Enhancer

Answer 14

can either increase or decrease rate of transcription, interacts with promoter to do so

Question 15

Exons

Answer 15

coding parts of gene

Question 16

Introns

Answer 16

noncoding parts of genes that are spliced out during processing

Question 17

GT/AG splice sites

Answer 17

occur in introns so spliceosome knows to cut them out

Question 18

GT splice site

Answer 18

occurs at the beginning of an intron or the 5’ splice site, upstream, donor

Question 19

AG splice site

Answer 19

occurs at the end of an intron or the 3’ splice site, downstream, acceptor

Question 20

If a promoter changes direction or position, will transcription take place as usual?

Answer 20

No, because promoters are direction and position dependent

Question 21

If an enhancer changes direction or position, will transcription take place as usual?

Answer 21

Yes, because enhancers are direction and position independent

Question 22

How does transcription stop?

Answer 22

a stem loop is formed by sequences of repeats near the 3’ end and it signals for transcription to stop, “the RNA polymerase gets lazy and falls off”

Question 23

How does transcription start?

Answer 23

The RNA polymerase attaches at the promoter and begins transcription

Question 24

How does translation start?

Answer 24

a start codon: AUG

Side note: translation does not always begin at the first exon.

Question 25

How does translation stop?

Answer 25

There are 3 stop codons, UGA is the one we talked about in class, the other 2 are UAA and UAG

Question 26

Gene arrangement

Answer 26

1. genes can be found in both directions, they’re just commonly written left to right in the western world
2. genes rarely overlap because there’s so much empty space found in genes, overlapping isn’t particularly useful
3. Clusters occur and they’re often similar genes or belong to the same gene family

Question 27

Polycistronic vs. monocistronic

Answer 27

polycistronic genes are a prokaryotic trait where 1 mRNA can make multiple proteins

monocistronic genes are a eukaryotic trait where 1 mRNA can only make 1 protein

Question 28

mRNA processing

Answer 28

1. 5’ 7-meG cap- protects from degradation
2. 3’ poly-A tail- signal near end of transcription prompts polyadenylation
   * **Side note- poly A tail important for nuclear export and stability of mRNA
3. splicing- introns are spliced out by spliceosomes (which follow the RNA polymerase along transcription path)

Question 29

alternative splicing

Answer 29

regulatory process where gene’s splice sites are obstructed by proteins—- this allows for multiple products to be made from same gene!