DNA, genes, alleles and RNA

Question 1

How is DNA stored in eukaryotic cells?

Answer 1

As chromosomes where the polynucleotide chain is wound up around histone proteins to form nucleosome
In the nucleus

Question 2

Where else in a eukaryotic cell is DNA found?

Answer 2

In mitochondria
In chloroplasts (if a plant cell)

Question 3

Features of eukaryotic nucleic DNA

Answer 3

Very long
Linear
Associated with proteins
DNA is only visible when it has condensed in mitosis otherwise exists as chromatin

Question 4

Features of DNA in chloroplasts/ mitochondria

Answer 4

Shorter molecule
Circular: no free ends
Not bound to histone proteins

Question 5

How is DNA stored in prokaryotic cells?

Answer 5

Found freely in the cytoplasm as long loops of DNA (additional plasmid loops)

Question 6

Features of DNA in prokaryotic cells

Answer 6

Shorter molecule
Circular: no free ends
Not bound to histone proteins
+ additional circular loops of plasmids

Question 7

What is a gene?

Answer 7

A base sequence in a section of DNA that codes for either:
-The amino acid sequence of polypeptide
-A functional RNA eg tRNA or rRNA

Question 8

How does the gene determine the protein?

Answer 8

The sequence of bases in a gene determines the transcribed mRNA (complementary base pairings) which in protein synthesis determines the amino acid sequence (primary structure). This determines tertiary structure based on bonds between R groups

Question 9

Genome

Answer 9

Complete set of genes in a cell inc mitochondrial and chloroplast DNA

Question 10

Proteome

Answer 10

Full range of proteins produced by the genome

Question 11

Cell proteome

Answer 11

The set of genes produced by a specific cell as a result of which genes are turned on and off

Question 12

Allele

Answer 12

An alternative version of the same gene
May possess a different nucleotide base sequence which alters the polypeptide encoded for by a gene

Question 13

where are genes/ alleles located on a chromosome?

Answer 13

On the same gene locus in the chromosome

Question 14

Homologous pair of chromosomes

Answer 14

Chromosomes that possess the same genes at the same gene loci: may or may not have the same alleles (therefore could potentially be a difference in nucleotide base pair)

Question 15

What is each chromosome in a homologous pair?

Answer 15

Maternal (from mother’s female gamete)
Paternal (from father’s male gamete)

Question 16

What do alleles at a fixed position encode for in a homologous pair?

Answer 16

The same characteristic or protein (eg hair colour, eye colour etc) but different variations eg black, brown etc

Question 17

2 Types of RNA

Answer 17

Messenger RNA (mRNA)
Transfer RNA (tRNA)

Question 18

Function of messenger RNA

Answer 18

Carries genetic code of DNA, to ribosomes in order to synthesise the polypeptide that the base sequence encodes for

Question 19

Structure of mRNA

Answer 19

Formed from condensation of RNA nucleotides to form phosphodiester bonds between each
Ribose sugar
Nucleotide bases: Adenine, Uracil, Cytosine, Guanine
Single polynucleotide strand = single helix molecule

Question 20

Function of tRNA

Answer 20

Carries the amino acids used to synthesise a polypeptide chain during translation

Question 21

Structure of tRNA

Answer 21

Single polynucleotide strand folded into clover shape: hydrogen bonds between complementary base pairs to hold it together
Has amino acid binding site at one end
Has 3 bases at other end known as anticodon