DNA

Question 1

nucleoside

Answer 1

sugar + base

Question 2

deoxyribose + thymine

Answer 2

=> deoxy-thymidine

Question 3

deoxyribose + adenine

Answer 3

deoxy-adenosine

Question 4

deoxyribose + guanine

Answer 4

deoxy-guanosine

Question 5

deoxyribose + cytosine

Answer 5

deoxy-cytidine

Question 6

telomeres

Answer 6

• highly repetitive DNA…
• that allow chromosomes ends to be replicated
• also protect ends of chromosomes being mistaken as broken

Question 7

origin of replication

Answer 7

• special seq where duplication of DNA begins
• each chromosome has many origins

Question 8

how is dsDNA molecule packaged in eukaryotic cells?

Answer 8

• packaged into chromosomes…
• through interactions with specialised proteins

Question 9

nucleoli

Answer 9

regions where…

• chromosomes carrying RNA cluster
• rRNAs are synthesised
• ribosomes are assembled

Question 10

2 types of chromatin

Answer 10

euchromatin:

• less compact DNA form (“open”)
• contains genes that are frequently expressed

heterochromatin:

• more compact
• contains DNA that is not transcribed

Question 11

genome

Answer 11

complete set of genes of organism

(all DNA in cell)

Question 12

genomics

Answer 12

• genome-wide analysis of…
• gene structure & expression

Question 13

gene

Answer 13

section of DNA that codes for a protein

Question 14

what does notation Tt mean to geneticists?

Answer 14

• 1 dom allele
• 1 recessive allele
• would see phenotype of T

Question 15

explain why RNA is less stable than DNA

Answer 15

• RNA chemically more reactive than DNA -> due to ribose sugar having 2’ OH group (attracts ox.)
• RNA more prone to mutation -> Cytosine deanimation to Uracil cannot be detected & repaired by RNA

Question 16

suggest why transcription may not take place

Answer 16

• RNA polymerase doesn’t bind to DNA without transcription factors present
• transcription factors must bind to control region

^if these things don’t happen => no transcription

Question 17

what types of RNA are transcribed from DNA?

Answer 17

• mRNA -> encodes proteins
• tRNA -> act in protein synthesis as adaptors between specific codon seqs on mRNA & a.a
• rRNA (ribosomal) -> forms part of ribosome & catalyses protein synthesis
• small RNAs (eg. small nuclear RNA snRNA) -> used in…
  -> pre-mRNA processing
  -> transport of proteins to ER
  -> other cellular processes
• miRNAs (micro) -> act in regulation of gene expression, inc. inhibiting translation & cleaving mRNAs

Question 18

the central dogma

Answer 18

DNA ——–> RNA ——-> a.a chain ——-> protein
transcription - translation - folding

Question 19

what do you need to replicate DNA in a test tube?

Answer 19

• DNA polymerase enzyme & Mg²⁺
• dNTPs (dATP, dCTP, dGTP, dTTP)
• single stranded template DNA
• primer 3’-OH

-> DNA synthesis will proceed in 5’ -> 3’ direction

Question 20

lagging strand synthesis in bacteria

Answer 20

1. primase synthesises short RNA oligonucleotides (primer) copied from DNA
2. DNA pol. 3 elongates RNA primers with new DNA
3. DNA pol. 1 removes RNA at 5’ end of neighbouring fragment & fills gap
4. DNA ligase connects adjacent fragments

Question 21

explain why E.coli (bacteria) has a faster bp/s than eukaryotes

Answer 21

E.coli has high processivity because DNA pol. attaches to sliding clamp