Topic 4A: DNA, RNA and Protein Synthesis

Question 1

How does Eurkaryotic cells store DNA?

Answer 1

As linear DNA molecules that are threadlike structures each made up of one long molecule of DNA and associated with histone proteins

Question 2

What do histone proteins do

Answer 2

Helps support the DNA the DNA is then coiled up very tightly to make a compact compound

Question 3

In eukaryotes what has its own DNA

Answer 3

mitochondria and chloroplasts, similar to prokaryotes DNA (circular and shorted)

Question 4

What is DNA like it prokaryotes

Answer 4

Shorter and circular, not wound around proteins condenses a to fit into the cells by super coiling

Question 5

What does DNA contain

Answer 5

Genes

Question 6

What is a gene

Answer 6

Sequence of DNA bases that codes for either a polypeptide or functional RNA

Question 7

What determines order of amino acids of a polypeptide

Answer 7

Order of bases in a gene, different polypeptides have different number and order of amino acids

Question 8

What is each amino acids coded by

Answer 8

For by 3 bases in a gene called triplet or codon

Question 9

How do you make polypeptide

Answer 9

DNA if first copied into messenger RNA, this is the first stage of protein synthesis

Question 10

Genes that don’t code for polypeptide codes for what?

Answer 10

Functional RNA

Question 11

What is functional RNA

Answer 11

RNA molecules other than mRNA which preform special tasks during protein synthesis

Question 12

Give 2 examples of functional RNA

Answer 12

tRNA and rRNA

Question 13

What is a genome

Answer 13

Full set of genes in a cell

Question 14

What is proteome

Answer 14

Full range of proteins that the cell is able to produce

Question 15

What are introns

Answer 15

Non-coding regions of DNA

Question 16

When are introns removed

Answer 16

During protein synthesis

Question 17

Why are introns removed during protein synthesis

Answer 17

So they don’t affect amino acid order

Question 18

What type of DNA doesn’t contain introns

Answer 18

Prokaryotic

Question 19

What are introns

Answer 19

Coding regions of DNA

Question 20

What are regions of multiple repeats

Answer 20

Sequence that repeats over and over again, they don’t code for AA either they are called non-coding multiple repeats

Question 21

What’s an allele

Answer 21

A different version of a gene

Question 22

How do chromosomes pair

Answer 22

In homologous pairs

Question 23

What are chromosomes like in homologous pairs

Answer 23

Same size and have the same genes, however they can have different alleles although alleles coding for the same will be found at the same fixed position (locus) on each chromosome

Question 24

What is protein synthesis

Answer 24

Production of proteins from the information contained within a cells DNA

Question 25

What’s the 2 stages of protein synthesis

Answer 25

Transcription and Translation

Question 26

What’s the structure of mRNA

Answer 26

Single polynucleotide strand

Question 27

Where is mRNA made and what does it do

Answer 27

Made during transcription it carries the genetic code from the DNA to ribosomes where it’s used to make a protein during translation

Question 28

What is tRNA involved in

Answer 28

Translation

Question 29

What does tRNA do

Answer 29

Carries AA that are used to make proteins to the ribosomes

Question 30

What’s the structure of tRNA

Answer 30

Single polynucleotide strand that’s folded into a clover shape, hydrogen bonds between specific base pairs hold the molecule in this shape Every tRNA has a specific sequence of three bases at one end called an anticodon It has an AA binding site at the other end

Question 31

What is step 1 of transcription

Answer 31

RNA polymerase attaches to the DNA, transcription starts when RNA polymerase attaches to the DNA double helix at the beginning of a gene The hydrogen bonds between the two DNA strands break separating the strands and the DNA molecule uncoils exposing some of the bases One is used to make a template

Question 32

What is step 2 of transcription

Answer 32

The RNA polymerase lines up free RNA nucleotides alongside exposes bases on the template stand The free bases are attracted to the exposed bases, specific complementary base pairing means that mRNA strand is a complementary copy Except T is replaced by U Once paired RNA polymerase joins them up forming mRNA molecule

Question 33

What is step 3 of transcription

Answer 33

RNA polymerase moves along the DNA, separating the stands and assembling the mRNA stand Hydrogen bonds between uncoiled strands reform once RNA polymerase has passed over them Coiling back into a double-helix

Question 34

What is step 4 of transcription

Answer 34

When RNA polymerase reaches a particular sequence of DNA called stop signal it stops making the mRNA and detaches from DNA mRNA moves out of the nucleus through a nuclear pore and attaches to a ribosome in cytoplasm where translation occurs

Question 35

What is meant by editing mRNA

Answer 35

In eukaryotes introns and exons are copied into the DNA mRNA containing both is called pre-mRNA, a process called splicing occurs where introns are removed and exons are joined together forming mRNA Taking place in nucleus, RNA leaves nucleus for translation

Question 36

What’s step 1 of translation

Answer 36

mRNA attaches itself to a ribosomes and tRNA molecules carry AA to it, ATP provides the energy needed for the bond between AA and tRNA molecule to form

Question 37

What is step 2 of translation

Answer 37

A tRNA molecule (carrying AA) with an anti-codon that’s complementary to the first codon on the mRNA attaches itself to the mRNA by complementary base pairing A second tRNA molecule attaches itself to the next codon on the mRNA in the same way

Question 38

What is step 3 of translation

Answer 38

The two AA attaches to the tRNA molecules are joined by a peptide bond The first tRNA molecule moves away, leaving its AA behind

Question 39

What is step 4 of translation

Answer 39

Third tRNA molecule binds to the next codon on the mRNA It’s AA binds to the first two and the second tRNA molecule moves away This process continues producing a chain of linked AA until there’s a stop signal on the mRNA molecule Polypeptide chain then moves away from the ribosomes and translation is complete

Question 40

What is the genetic code

Answer 40

Sequence of base triplets in mRNA which code for specific AA In the genetic code each base is read in sequence, separate from triplet before it and after it

Question 41

What are the 3 main features of the genetic code (explained)

Answer 41

Non-overlapping: Base triplets don’t share their bases Degenerate: there’s more possible combinations of triplets than there are AA meaning some AA are coded for by different combinations Universal: same specific base triplets code for the same AA in all living things