3.4.1 DNA, genes and chromosomes

Where is most eukaryotic DNA found

in the nucleus

where is the minority of eukaryotic DNA found

in the mitochondria and chloroplasts

define chromatin

DNA tightly coiled around histone proteins

define chromosomes

chromatin in linear lengths

Define centromere

The narrow region joining chromatids

What are chromosomes made of

One very long, condensed DNA molecule associated with proteins

What is the role of histone proteins

To organise and condense the DNA so it fits in the nucleus

what do chromosomes contain

A series of genes

Describe a telomere

A protective structure that seals the end of the chromatid

what is the name of the protein involved in eukaryotic DNA

histone proteins

what do genes code for

a polypeptide or a functional RNA molecule

Name the two functional RNA molecules

tRNA or rRNA

define intron

a non-coding region of a gene

What is the name of the process of removing introns

Splicing

what occurs during protein synthesis

the introns are removed leaving mRNA as exons

what does the presence of introns in genes mean

that most of the DNA is non coding

describe structure of prokaryotic DNA

circular, with no introns or histone proteins

give two examples of DNA which is ‘prokaryotic in nature’

mitochondria, chloroplasts

Define a plasmid

Small circular DNA molecules containing a few genes

What specific genes are found in plasmids

Genes for antibiotic resistance

When may plasmids be used and why

When genes are required quickly or in an emergency, as they are more accessible

define genome

all the genes present in a cell or organismefid

define proteome

all the polypeptides a cell is able to produce

what three things is the genetic code described as

universal, degenerate, non-overlapping

define universal

same in all living organisms

define degenerate

many amino acids coded for by more than one triplet codon

define non-overlapping

each nucleotide is only used in one codon

define a codon

3 bases

What is DNA in mitochondria and chloroplasts similar to

DNA of a prokaryote

Define a gene

A base sequence of DNA that codes for the amino acid sequence of a polypeptide or functional RNA molecule

Describe the purpose of mRNA

To code for the polypeptide chain

Describe the purpose of tRNA

To collect the corresponding amino acid

Describe the purpose of rRNA

To form part of the ribosomes structure

Define a locus

The position of a gene on a chromosome

What difference do alleles of genes have

Different nucleotide sequences with the same loci

Describe differences between DNA and mRNA

DNA is longer, ribose/deoxyribose sugar, single/double stranded, uracil/thymine

Describe prokaryotic DNA

Double stranded, single, circular chromosomal DNA molecule not associated with proteins