DNA,Genes & Protein Synthesis

Question 1

Gene definition

Answer 1

Section of dna that contains the coded information for making polypeptides and functional RNA

Question 2

Locus definition

Answer 2

Gene located at a particular position on DNA molecule

Question 3

Explain Degenerate DNA

Answer 3

Most amino acids are coded by more than one triplet of bases - this is useful because some mutations may not affect the polypeptide chain and hence enzyme structure.

Question 4

Non - overlapping DNA

Answer 4

A triplet is always read in one direction hence each base in a sequence is only read once so less likely mutations occur?

Question 5

Universal DNA

Answer 5

same system in most organisms so indirect evidence for evolution

Question 6

In eukarya most DNA are coding/ non - coding - produce mRNA with introns and exons?

Answer 6

Non coding (introns)

Question 7

Differences between prokaryotic and eukaryotic dna MOLECULES

Answer 7

Pro is shorter euk is longer
Pro can firm circular dna and plasmids euk is linear
Pro is not associated with proteins euk is associated with histones

Question 8

Describe how a DNA molecule and it’s associated proteins form a chromosome and benefit

Answer 8

Chromosomes appear as two threads. Each thread is called a chromatid. DNA in chromosomes are held together by histones - looped aroudn histones and tightly coiled so a lot of DNA is condensed into a single histone.

Question 9

Chloroplasts and mitochondria also contain DNA - what type and describe

Answer 9

Prokaryotic dna

Short, circular and not associated with proteins

Question 10

Explain how a sequence of three bases code for a specific amino acid

Answer 10

Three bases are transcribed into a codon, which is specific to an amino acid that is complementary to the anticodon of tRNA

Question 11

Genome definition

Answer 11

The complete set of genes in a cell

Question 12

Proteome definition

Answer 12

The full set of proteins a cell is able to produce.

Question 13

Homologous pairs

Answer 13

Maternal and paternal chromosomes

Question 14

Allele definition

Answer 14

One of a number of alternative forms of a gene.

Question 15

Two types of rna important to protein synthesis are

Answer 15

mRNA

tRNA

Question 16

RNA (both types) are polymers made of mono nucleotides. What is the structure of the nucleotide

Answer 16

Ribose bonded to a phosphate group and organic bases adenine cytosine guanine and uracil

Question 17

mRNA structure

Answer 17

Single long strand arranged in a single helix

Question 18

DNA vs mRNA structure

Answer 18

DNA is double stranded alpha helix, mRNA is a single stranded helix
mRNA has uracil instead of thymine
Ribose vs deoxyribose in dna

Question 19

tRNA structure

Answer 19

80 nucleotides
Single stranded chain folded into clover shape with one strand extending beyond the other
Paired bases inside present so hydrogen bonding
Unpaired based on outside
Specific amino acid binding site
Amino acid is complementary to anticodon at opposite end
Anticodon is complementary to mRNA codon

Question 20

Transcription process

Answer 20

RNA polymerase unzips and unwinds the part of the DNA molecule needed by breaking hydrogen bonds between complementary base pairs. This is a local unwinding of molecule only where needed.
Exposed nucleotides on template strand attract free activated RNA nucleotides from from the cytoplasm/ nucleoplasm?
As RNA polymerase moves along the DNA strands, it catykses the formation of phosphodiester bonds between RNA nucleotides.
Enzyme zips molecule up behind it (reforms hydrogen bonds)
Forms pre - mRNA

Question 21

Splicing in eukaryotes or prokaryotes?

Answer 21

Eukaryotes

Question 22

Splicing

Answer 22

Pre - mRNA strand has introns which are non - coding regions. Before leaving nucleons, introns are cut out and exons are joined together by a mature mRNA, which leaves the nucleus through nuclear pore.

Question 23

In prokaryotes transcription results in the

Answer 23

Direct formation of mRNA

Question 24

How does tRNA become charged?/ use of ATP in translation

Answer 24

Specific enzyme binds to ATP and specific amino acid
ATP loses two phosphate molecules becoming AMP and specific tRNA molecule is recruited.
tRNA covalently bonds to amino acid and AMP is released
ATP provides energy for covalent bond to form

Question 25

Translation

Answer 25

Ribosome attaches to mRNA at start codon.
Charged tRNA molecule contains complementary anticodon and its specific amino acid
Anticodon is attracted to exposed base pairs of mRNA
Charged tRNA with complementary anticodon pairs with next codon on mRNA
Two tRNAs are sitting next to each other in ribosome sites
Enzyme activity within the large ribosome sub unit joins the amino acids using ATP for peptide bond formation
First tRNA molecule is uncharged and leaves ribosome to find specific amino acid againand the next charged tRNA molecule enters ribosome site
Ribosome detaches from polypeptide chain upon reaching stop codon. Ribosome, tRNA and mRNA all separate now.
Polypeptide chain folds into secondary and tertiary structure.

Question 26

Is mRNA a “forever” molecule

Answer 26

No breaks down easily to prevent over synthesis of proteins

Question 27

Ribosomes formed?

Answer 27

Translation but specify two subunits

Question 28

DNA is an info carrying molecule explain

Answer 28

Genetic information and instructions on protein synthesis

Question 29

RNA is an info carrying molecule

Answer 29

Transfer DNA genetic instructions to ribosomes to form polypeptide chains