3.4.1 DNA, Genes and Chromosomes

Question 1

Describe DNA molecules in prokaryotic cells?

Answer 1

Short
Circular
Not associated with proteins

Question 2

How does protein synthesis differ in prokaryotic and eukaryotic cells?

Answer 2

Transcription occurs in the nucleus in a eukaryotes; transcription occurs in the cytoplasm of a prokaryote
Translation occurs in the cytoplasm of eukaryotes and prokaryotes

Question 3

Where is DNA found in prokaryotic cells?

Answer 3

Loose in the cytoplasm

Question 4

Where is DNA found in eukaryotic cells?

Answer 4

In a membrane bound nucleus

Question 5

In what form is the DNA in a prokaryotic and eukaryotic cell?

Answer 5

Prokaryotic- a single loop (with plasmids)

Eukaryotic- linear chromosomes

Question 6

Is the DNA is prokaryotic and eukaryotic cells associated with proteins?

Answer 6

Prokaryotic- no (not a chromosome)

Eukaryotic- yes, wrapped around histones

Question 7

What is the length of the DNA molecules in a prokaryote and eukaryotes?

Answer 7

Prokaryote- shorter

Eukaryote- longer

Question 8

Where is DNA found in eukaryotic cells?

Answer 8

Nucleus
Mitochondria
Chloroplasts

Question 9

How is DNA thought to have got into mitochondria and chloroplasts?

Answer 9

Endosymbiotic theory

Mitochondria and chloroplasts were once free living prokaryotes that were engulfed by a cell

Question 10

Define chromosome.

Answer 10

Thread like structure found in the nucleus of eukaryotic cells
Consists of a single molecule of DNA
Highly wound around protein molecules called chromatin

Question 11

What is a gene?

Answer 11

A section of DNA that codes for the amino acid sequence of one polypeptide

Question 12

What is a locus?

Answer 12

The position on a particular chromosome where you find a gene

Question 13

What is a homologous pair?

Answer 13

Chromosome pairs
One from each parent
Similar in length, gene position and centromere location

Question 14

How many pairs of chromosomes does a human have?

Answer 14

23

Question 15

What is an allele?

Answer 15

The different forms a gene can take

Question 16

Define diploid.

Answer 16

A cell that contains two sets of chromosomes

Question 17

What is a diploid number?

Answer 17

The number of chromosomes in a cell

Abbreviated to 2n (where n is the number of chromosomes)

Question 18

Define homozygous.

Answer 18

Where both alleles for a gene are the same

Question 19

Define heterozygous.

Answer 19

Where the alleles for a gene are different

Question 20

What does it mean if a cell is haploid?

Answer 20

Contains one complete set of chromosomes

Question 21

Give an example of a haploid cell?

Answer 21

Gametes

Question 22

When are haploid cells produced?

Answer 22

Meiosis

Question 23

What is the haploid number?

Answer 23

Number of chromosomes within the cell that is the set

Question 24

Define genome.

Answer 24

The full set of genes in a cell

Question 25

Define proteome.

Answer 25

The full range of proteins coded for by the genes

Question 26

Define karyotype.

Answer 26

The number and appearance of chromosomes in the nucleus of a eukaryotic cell

Question 27

Why isn’t DNA stored in the nucleus of a prokaryotic cell?

Answer 27

They have no nucleus!

Question 28

What is the purpose for the cooling of DNA in a chromosome?

Answer 28

So it is easy to separate/ unravel DNA without damaging it | For DNA replication

Question 29

Describe the structure of a chromosome.

Answer 29

A DNA double helix strand forms a chromatin fibre This wraps around histone proteins Histone proteins coil to make a chromatin fibre These form loops Loops form rosettes These coil together One chromatid is 10 coils long

Question 30

Define exon.

Answer 30

Sequences of bases in a gene that code for a sequence of a amino acids in a protein

Question 31

Define intron.

Answer 31

Non-coding DNA which can be found between genes in multiple repeats or within genes

Question 32

Why is DNA a ‘universal code’?

Answer 32

DNA is used in virtually all organisms as the material of inheritance

Question 33

What is a codon?

Answer 33

The sequence of three bases that codes for one amino acid

Question 34

What is degenerate code?

Answer 34

Amino acids are coded for by more than 1 codon

Question 35

What makes DNA ‘non-overlapping’?

Answer 35

Each base in the sequence is read only once so the code is non-overlapping

Question 36

Why are three bases needed to core for each amino acid?

Answer 36

There are 4 bases If one base coded for one amino acid there would only be 4 possibilities If they were in pairs there would only be 16 possibilities We need 20 different codes With 3 bases there are 64 possible combinations

Question 37

What is an advantage to a cell of having degenerate code?

Answer 37

If there is a substitution mutation in the third base of a codon, the impact will be small on the amino acid made (eg GGA and GGG codes for the same thing)

Question 38

Which bases are involved in the triplet code table?

Answer 38

ATGC

Question 39

Ow many amino acids would be coded for from AAACACTTGGTC?

Answer 39

4

Question 40

What do polypeptides combine to produce?

Answer 40

Proteins