DNA,RNA and Protein Synthesis-Topic 4A

Question 1

What are chromosomes?

Answer 1

Thread like structures each made up of one long molecule of DNA

Question 2

Where are chromosomes found?

Answer 2

In the nucleus

Question 3

How do Prokaryotes differ from Eukaryotes when storing DNA? (2 differences + 1 similarity)

Answer 3

Shorter
Circular
However both carry DNA as chromosomes

Question 4

What forms the primary structure of a protein?

Answer 4

The sequence of amino acids in a polypeptide

Question 5

What determines the order of amino acids in a polypeptide?

Answer 5

The order of bases in a gene.

Question 6

What is a gene?

Answer 6

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

Question 7

Each amino acid is coded for by …….. …….

Answer 7

A sequence of three bases called a triplet.

Question 8

What is the first stage of protein synthesis?

Answer 8

DNA is copied into messenger RNA

Question 9

What is functional RNA?

Answer 9

RNA molecules (other than mRNA) which perform special tasks In protein synthesis e.g. tRNA

Question 10

What is a cell’s genome?

Answer 10

The complete set of genes in the cell.

Question 11

What is a cell’s proteome?

Answer 11

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

Question 12

The genetic code is degenerate. What does this mean?

Answer 12

(some) amino acids have more than one coding triplet

Question 13

The genetic code is Universal. What does this mean?

Answer 13

The same codons code for the same amino acids in all organisms.

Question 14

What is a benefit of the genetic code being no-overlapping?

Answer 14

Each base in the sequence is part of only one codon.

Question 15

What are introns?

Answer 15

Sections of non coding DNA within a gene.

Question 16

What are exons?

Answer 16

Coding sections of DNA within a gene.

Question 17

Why are introns removed during protein synthesis?

Answer 17

So they don’t affect the amino acid order.

Question 18

What are Non-coding repeats?

Answer 18

DNA sequences that repeat over and over but don’t code for amino acids either.

Question 19

Genes can exist in different forms called…

Answer 19

Alleles.

Question 20

What do alleles do?

Answer 20

Code for slightly different versions of the same polypeptide. (this is because the order of bases in each allele is slightly different)

Question 21

Humans have …… pairs of chromosomes

Answer 21

23

Question 22

Pairs of matching chromosomes are called….

Answer 22

homologous pairs

Question 23

In a homologous pair both chromosomes are the same size and have the same ……. but may have different …….

Answer 23

In a homologous pair both chromosomes are the same size and have the same genes but may have different alleles.

Question 24

Alleles coding for the same characteristic will be found at the same ………. …… (…….) on each chromosome in a homologous pair.

Answer 24

Alleles coding for the same characteristic will be found at the same fixed position (locus) on each chromosome in a homologous pair

Question 25

Mitochondria and chloroplasts have similar DNA to …….. ……

Answer 25

Mitochondria and chloroplasts have similar DNA to prokaryotic DNA.

Question 26

What is a DNA triplet?

Answer 26

3 bases in a gene coding each amino acid.

Question 27

Name the two types of RNA

Answer 27

mRNA and tRNA

Question 28

What stage is mRNA made?

Answer 28

During transcription

Question 29

What is the role of mRNA?

Answer 29

Carries the genetic code from the DNA to the ribosomes where it’s used to make a protein during translation.

Question 30

What is mRNA?

Answer 30

A single polynucleotide strand

Question 31

What are codons?

Answer 31

3 adjacent bases, in mRNA

Question 32

Name the first stage of protein synthesis?

Answer 32

Transcription

Question 33

Name the second stage of protein synthesis

Answer 33

Translation

Question 34

tRNA is involved in…….

Answer 34

Translation

Question 35

What does tRNA do?

Answer 35

Carries the amino acids that are used to make proteins , to the ribosomes

Question 36

What is tRNA?

Answer 36

Single nucleotide strand folded into a clover shape

Question 37

How is a tRNA molecule held in it’s shape?

Answer 37

Hydrogen bonds between specific base pairs hold the molecule in this shape.

Question 38

What is an anticodon?

Answer 38

A specific sequence of 3 bases on tRNA.

They also have an amino acid binding site on the other end.

Question 39

Why are DNA strands produced in opposite directions?

(use enzyme action knowledge) [4]

Answer 39

Antiparallel strands
The shapes of nucleotides are different
Enzymes have an active site which is a specific shape.
Only substrates with a complementary shape can bind with the active site of enzyme.

Question 40

Why can nucleotides only be added in 5’-3’ direction?

Answer 40

DNA Polymerase
is specific
so only complementary on the 5’ end of the strand.
shapes of 5’ end & 3’ end are different so polymerase cannot work on 3’ end.

Question 41

Describe how the DNA in a eukaryotic cell is arranged so that it can fit into the nucleus?

Answer 41

DNA wound around histone proteins

Tightly coiled into compact chromosomes

Question 42

Describe the structure of tRNA

Answer 42

Single polynucleotide strand folded into a clover shape. Hydrogen bonds between the specific base pairs hold the molecule in this shape.

Question 43

Describe the structure of mRNA

Answer 43

Single polynucleotide strand. 3 adjacent bases on strand = codon

Question 44

mRNA strands contains introns and exons are called….

Answer 44

pre-mRNA

Question 45

What is splicing?

Answer 45

Introns are removed and the exons joined together forming mRNA strands

Question 46

Where does splicing occur?

Answer 46

The nucleus

Question 47

Why does splicing not happen in prokaryotes?

Answer 47

No need for splicing because there aren’t any introns in prokaryotic DNA.