✅8 - DNA, Genes and Protein Synthesis

Question 1

What is a gene?

Answer 1

A section of DNA that contains the coded information for making polypeptides and functional RNA

Question 2

What is a locus?

Answer 2

The particular positions of a gene in a section of DNA

Question 3

Why was it suggested that there were a minimum of three bases coding for each amino acid?

Answer 3

Only 20 amino acids occur in proteins
Each amino acid must have its own code
There are only four bases
4^2 is 16, while 4^3 is 64 amino acids

Question 4

Why is the code degenerate?

Answer 4

Because most amino acids are coded for by more than one triplet

Question 5

How is the triplet always read?

Answer 5

In one direction

Question 6

What is always the first triplet in an amino acid sequence?

Answer 6

That coding for the amino acid methionine

Question 7

Why is the code non-overlapping?

Answer 7

Because each base sequence is only read once, as triplets rather than individually

Question 8

Why is the code universal?

Answer 8

Because with a few minor exceptions each triplet codes for the same amino acid in all organisms - indirect evidence for evolution

Question 9

What are introns?

Answer 9

Triplets which do not code for any amino acids

Question 10

What are exons?

Answer 10

Triplets that are expressed

Question 11

What are histones?

Answer 11

Proteins associated with DNA

Question 12

What is a chromatid?

Answer 12

A thread of DNA which makes up a chromosome

Question 13

What are homologus pairs?

Answer 13

One chromosome from each parent in a pair, with the same genes but not necessarily the same alleles

Question 14

What is the human chromosome number?

Answer 14

46

Question 15

What is an allele?

Answer 15

One of a number of alternative forms of a gene

Question 16

What is mRNA?

Answer 16

Messenger RNA

Question 17

What is the relative size of mRNA?

Answer 17

Small enough to leave the nucleus through the nuclear pores and to enter the cytoplasm

Question 18

What is a codon?

Answer 18

A sequence of three bases on mRNA that codes for a single amino acid

Question 19

What is a genome?

Answer 19

The complete set of genes in a cell, including those in mitochondira and/or chloroplasts

Question 20

What is a proteome?

Answer 20

The full range of proteins produced by the genome

Question 21

What is RNA made up of?

Answer 21

Ribose
One organic base
A phosphate group

Question 22

What are the two types of RNA important to protein synthesis?

Answer 22

mRNA

tRNA

Question 23

What is the base sequence of mRNA determined by?

Answer 23

The sequence of bases on DNA

Question 24

What are the complementary base pairings for RNA?

Answer 24

C + G

A + T/U

Question 25

What is transcription?

Answer 25

When a complementary section of part of the DNA sequence is made in the form of a molecule of pre-mRNA

Question 26

What is translation?

Answer 26

The mRNA is used as a template to which complementary tRNA molecules attach and the amino acids they carry are linked to form a polypeptide

Question 27

How is mRNA made from pre-mRNA?

Answer 27

Through splicing

Question 28

Which enzyme builds the pre-mRNA strand?

Answer 28

RNA polymerase

Question 29

Why do mRNA molecules leave the nucleus via nuclear pores?

Answer 29

Because they are too large to diffuse out

Question 30

Where does the ribosome attache to?

Answer 30

The starting codon at the end of the mRNA molecule

Question 31

Where does the tRNA molecule move to?

Answer 31

The ribosome, and attaches to the complementary codon on the mRNA

Question 32

How many tRNA molecules does the ribosome bring together at once?

Answer 32

Two

Question 33

What is used to form peptide bonds between the two amino acids?

Answer 33

An enzyme and ATP

Question 34

What happens as the third amino acid is attached to the sequence?

Answer 34

The first tRNA is released and it is free to collect another amino acid

Question 35

How many ribosomes can pass behind the first?

Answer 35

Up to 50