DNA And Chromosomes

Question 1

Define locus

Answer 1

The specific position of a gene on a chromosome

Question 2

Define histone

Answer 2

A protein that DNA wraps tightly around to form a chromosome

Question 3

Define telomere

Answer 3

Region of repetitive nucleotide sequences at each end of a chromosome which protect the ends of a chromosome from deterioration or from fusion with neighbouring chromosomes

Question 4

Define homologous chromosomes

Answer 4

Two chromosomes that determine the same genetic characteristics

Question 5

Define allele

Answer 5

A version of a gene

Question 6

Define chromatids

Answer 6

One of the identical halves of a chromosome that has been replicated in preparation for cell division

Question 7

Which type of DNA contains non coding DNA/molecules? Why?

Answer 7

In the majority of eukaryotes, lots of the nuclear DNA does not code for polypeptides
Prokaryotic doesn’t contain it as it is too short

Question 8

What are non coding base sequences? Where are they found

Answer 8

DNA which is not useful for coding amino acid sequences/polypeptides
They are found between genes (eg example non coding multiple repeats) and found within genes (introns)

Question 9

What is transcription

Answer 9

The process of turning DNA in to mRNA
It is the first step of proteinsynthesis

Question 10

Describe mRNA

Answer 10

Single stranded
Contains a ribose sugar
Contains uracil

Question 11

What does mRNA stand for

Answer 11

Messenger RNA

Question 12

What does tRNA stand for

Answer 12

Transfer RNA

Question 13

What does every tRNA have? What are they complementary to

Answer 13

3 bases called an anticodon
They are complementary to codons on an mRNA molecule

Question 14

Is tRNA single or double stranded

Answer 14

Single stranded, but is folded

Question 15

What type of bonds hold together the 5’ and 3’ end on a tRNA molecule? What shape does this make?

Answer 15

Hydrogen
Clover leaf shape

Question 16

How many polynucleotides do DNA, mRNA and tRNA have

Answer 16

DNA - 2
mRNA - 1
tRNA - 1

Question 17

Which out of DNA, mRNA and tRNA have hydrogen bonds

Answer 17

DNA - yes, between strands
mRNA - no, single stranded
tRNA - yes, between folds of the single strand

Question 18

Which out of DNA, mRNA and tRNA is the largest

Answer 18

DNA - largest
mRNA - middle
tRNA - smallest

Question 19

Where is DNA, mRNA, tRNA found in the cell

Answer 19

DNA - nucleus
mRNA - made in the nucleus, found throughout the cell
tRNA - cytoplasm

Question 20

What type of pentose sugar does DNA, mRNA and tRNA have

Answer 20

DNA - dioxyribose
mRNA - ribose
tRNA - ribose

Question 21

What shape is DNA, mRNA and tRNA

Answer 21

DNA - double helix
mRNA - single strand
tRNA - single strand folded into a clover leaf shape

Question 22

How does the quantity of DNA, mRNA and tRNA in a cell differ

Answer 22

DNA - it is all constant for all cells
mRNA and tRNA - varies from cell to cell and with metabolic activity

Question 23

What is the chemical stability like in DNA, mRNA and tRNA

Answer 23

DNA - very stable
mRNA - chemically unstable
tRNA - unstable, but more stable than mRNA

Question 24

What are the similarities between DNA in eukaryotes and prokaryotes

Answer 24

Nucleotide structure is identical in both with a deoxyribose attached to a phosphate and a base
In both, adjacent nucleotides are joined by phosphodiester bonds and complementary bases are joined by hydrogen bonds
DNA in the mitochondria/chloroplasts have a similar structure to DNA in prokaryotes which is short, circular and isn’t just associated with proteins

Question 25

What are the differences between DNA in eukaryotes and prokaryotes

Answer 25

Eukaryotic DNA is longer than prokaryotic Eukaryotic DNA is linear, prokaryotic is circular Eukaryotic DNA is associated with histone proteins, prokaryotic isn’t Eukaryotic DNA contains introns, prokaryotic doesn’t

Question 26

What is a chromosome? Where does it appear

Answer 26

A long, linear DNA and its associated histone proteins It appears in the nucleus of eukaryotic cells

Question 27

What is a gene?

Answer 27

A sequence of DNA (nucleotide) bases that codes for the amino acid sequence of a polypeptide or a functional RNA

Question 28

What are introns? Where are they found

Answer 28

Base sequence of a gene that doesn’t code for amino acids, found in eukaryotic cells

Question 29

What are exons?

Answer 29

Base sequence of a gene coding for amino acid sequences in a polypeptide

Question 30

Describe the nature of the genetic code

Answer 30

Triplet code - a sequence of 3 DNA bases called a triplet, which codes for a specific amino acid Universal - the same base triplets code for the same amino acids in all organisms Non overlapping - each base is a part of only one triplet so each triplet is read as a discrete unit Degenerate - an amino acid can be coded for by more than one base triplet