2.3 Genes, DNA, RNA

Question 1

What is a nucleotide?

Answer 1

Building blocks of nucleic acids = a nitrogenous base; a sugar; one or more phosphates

Question 2

Name the types of nitrogenous base are there and how they are grouped?

Answer 2

Purines:
Adenine
Guanine

Pyrimidines:
Cytosine
Thymine
Uracil

Question 3

What are the 2 types of sugar?

Answer 3

Deoxyribose & Ribose

Question 4

What is DNA?

Answer 4

Deoxyribonucelic acid

a double stranded helix of 4 deoxyribonucleotides (A, T, C & G) linked together through phosphodiester bonds

Question 5

What is RNA?

Answer 5

single stranded chains of 4 deoxyribonuleotides (A, U, C & G)

Question 6

What is the tertiary structure of RNA?

Answer 6

It forms a ‘clover leaf’

Question 7

What is Pre-mRNA or heteronuclear RNA (hnRNA)?

Answer 7

the primary transcripts produced from DNA during transcription - processed and shortened to produce mature mRNA

Question 8

What is Messenger RNA (mRNA)?

Answer 8

represents the mature RNA transcripts of the gene as a template during translation

Question 9

What is Transfer RNA (tRNA)?

Answer 9

specific adaptors during translation

at least 20 forms that are specific for each amino acid

Question 10

What is Ribosomal RNA (rRNA)?

Answer 10

large structural or enzymatic (ribozymes) RNA molecules that determine the structure and function of the ribosome - act as a framework for ribosomal protein binding

Question 11

What is Small nuclear RNA (snRNA)?

Answer 11

found in large quantities in the nucleus

many are ribozymes
involved in RNA processing

Question 12

What is Small interfering RNA (siRNA)?

Answer 12

short double stranded RNA molecules which act to suppress gene expression

Question 13

What is the usual start codon in a mammalian gene?

Answer 13

AUG (ATG) which codes for methionine

Question 14

What are the stop codons of a mammalian gene?

Answer 14

UAA, UAG or UGA - these do not encode any amino acid but signal to stop translation

Question 15

How is a nuclosome formed?

Answer 15

DNA is wrapped around nucleosomes through linker DNA - a repeating series of nucleosomes and their connections are referred to as ‘beads on a string’

Question 16

What is a nuclosome?

Answer 16

The fundamental unit of Chromatin - a complex of DNA & proteins that forms chromosomes

Question 17

What is a histone octamer?

Answer 17

the eight protein complex found at there centre of a nucleosome - assembles when a tetramer containing 2 copies of both H3 and H4 joins with a 2 H2A/H2B dimers

Question 18

What are promotors?

Answer 18

regions of DNA upstream of the gene that can activate gene expression and RNA polymerase II binding when activates by transcription factors

Question 19

What are enhancers?

Answer 19

regions of DNA remote from the gene that enhance the efficiency of gene expression - the remote regions are placed in physical proximity to the gene by various activators and co-activators

Question 20

What are exons?

Answer 20

regions that determine mRNA sequence which encode the protein

Question 21

What are introns?

Answer 21

non-coding regions interspersed between the exons

Question 22

What does a spliceosome do?

Answer 22

During transcription the RNA copy that is made (primary transcript) contains both interons and axons = pre-mRNA

The spliceosome splices the primary transcript to eliminate introns = mRNA

This occurs within the nucleus