DNA, RNA and Protein Synthesis

Question 1

What is DNA like in Eukaryotic Cells?

Answer 1

• linear existing in chromosomes

Question 2

The DNA molecule in Eukaryotic cells is long, so what happens?

Answer 2

It has to be wound up so it can fit into the nucleus - it is wound up around proteins called Histones which help to support it.

Then the DNA had protein are coiled up very tightly to make a compact chromosome.

Question 3

Mitochondria and Chloroplasts also have their own DNA, what’s different?

Answer 3

They’re circular and shorter like DNA in Prokaryotes.

Question 4

What is DNA like in Prokaryotic Cells?

Answer 4

Shorter and circular - and the DNA isn’t wound around Histones.
It condenses to fit into the cell by supercoiling.

Question 5

What is a gene?

Answer 5

A sequence of DNA bases that codes for either a polypeptide or functional RNA.

Question 6

Different polypeptides have a different…

Answer 6

Number and order of amino acids - the order of bases in a gene determine the order of amino acids in a particular polypeptide.

Question 7

Each amino acid is coded for by…

Answer 7

A sequence of 3 bases in a gene called a triplet.

DNA triplet = one amino acids.

Question 8

What about genes that don’t code for a polypeptide code?

Answer 8

They code for a functional RNA instead - (molecules other than mRNA)

Question 9

What is a cell’s genome?

Answer 9

The complete set of genes in the cell.

Question 10

What is a cell’s proteome?

Answer 10

The full range of proteins that the cell is able to produce.

Question 11

In Eukaryotic DNA, what can we find?

Answer 11

We can find sections of genes that don’t code for amino acids.

These are called INTRONS.

Question 12

All the bits of a gene that do code for amino acids are called…

Answer 12

EXONS.

Question 13

What happens to Introns during protein synthesis?

Answer 13

They’re removed so they don’t affect the amino acid order.

Question 14

What else do Eukaryotic DNA contain?

Answer 14

Regions of multiple repeats outside of genes.

These don’t code for amino acids either = so they’re called non-coding repeats.

Question 15

What are Alleles?

Answer 15

More than one form of a gene.

Question 16

What is the order of bases in each allele like?

Answer 16

Slightly different so they code for slightly different versions of the same polypeptide.

Question 17

Pairs of matching chromosomes are called…

Answer 17

Homologous pairs.

Question 18

What’s a homologous pair like?

Answer 18

Both chromosomes are the same size and have the same genes although they could have different alleles.

Question 19

Give 2 types of RNA:

Answer 19

mRNA

tRNA

Question 20

Where is mRNA made and what does it do?

Answer 20

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

Question 21

mRNA is…

Answer 21

A single polynucleotide strand.

Question 22

Where is tRNA involved and what does it do?

Answer 22

Translation - carries the amino acids that are used to make proteins to the ribosomes.

Question 23

tRNA is…

Answer 23

A single polynucleotide strand that’s folded into a clover shape - H bonds.

Question 24

Every tRNA molecule has…

Answer 24

A specific sequence of three bases at one end called and anticodon.

Question 25

Every mRNA molecule has…

Answer 25

3 bases are called codons.

Question 26

Transcription: (4)

Answer 26

1) RNA polymerase attaches to the DNA double helix at the beginning of a gene.
2) H bonds between DNA strands break = uncoils, exposing bases = one strand used as a template to make an mRNA copy.
3) RNA polymerase lines up free RNA Nucleotides alongside exposed bases on template strand =specific complimentary base pairing = joined together by RNA polymerase forming mRNA.
4) RNA polymerase moves along the DNA, separating the strands and assembling mRNA = hydrogen bands reform and goes into double helix.

Question 27

What happens when RNA polymerase reaches a stop signal?

Answer 27

It stops making mRNA and detaches from the DNA.

Question 28

What’s the difference between mRNA and pre-mRNA?

In EUKARYOTES

Answer 28

pre-mRNA contains both introns and exons = splicing takes place and introns aré removed and exons aré joined together forming mRNA strands.

SPLICING.

Question 29

Does splicing take place in Prokaryotes?

Answer 29

No because there are no introns in prokaryotic DNA so there’s no need for it.

Question 30

Translation occurs at…

Answer 30

The ribosomes in the cytoplasm.

Question 31

What happens in translation?

Answer 31

Amino acids are joined together to make a polypeptide chain.

Question 32

Translation: (4)

Answer 32

1) the mRNA attaches to a ribosome and tRNA carry amino acids to it - bond between amino acid and tRNA form.
2) a tRNA molecule with an anticodon complementary to the first codon on the mRNA attaches to mRNA = base pairing = happens again to next tRNA molecule.
3) the two amino acids attaches to the tRNA molecules are joined by a peptide bond = first tRNA molecule moves away leaving its amino acid behind.
4) a third tRNA molecule binds to the next codon on the mRNA = it’s amino acid binds to the first two and the second tRNA molecule moves away.

Question 33

When does the process of translation finish?

Answer 33

When there’s a stop signal on the mRNA molecule.

Question 34

Genetic Code is Degenerate:

Answer 34

There are more possible combos of triplets than there are amino acids.

Question 35

Genetic Code is Universal:

Answer 35

The same specific base triplets Code for the same amino acids in all living things.

Question 36

Genetic Code is Non Overlapping:

Answer 36

Each base triplet is read in sequence, separate from the triplet before it and after it.