DNA, GENES & CHROMOSOMES Key Terms
3.4 GENETIC INFORMATION, VARIATION & RELATIONSHIPS Gene
BETWEEN ORGANISMS
Locus
Gene MISSESTRUCH 2020 Allele
Chromosome
A gene is a section of DNA that contains a code for making
DNA
a polypeptide and functional RNA. The code is a specific
sequence of bases. Polypeptides make proteins and so genes
determine the proteins of an organism.
The location of a particular gene on a chromosome is called the locus.
Allele Chromosome
An allele is one of a number of alternative forms In a eukaryotic cell nucleus, DNA is stored as
of a gene. Most genes occur in two (an allelic chromosomes. Humans have 23 pairs of
pair), but occasionally in more different forms chromosomes and 46 in total.
(multiple alleles).
1
MISSESTRUCH 2020
,DNA, GENES & CHROMOSOMES Key Terms
3.4 GENETIC INFORMATION, VARIATION & RELATIONSHIPS Homologous chromosome
BETWEEN ORGANISMS
Chromosome
Homologous Chromosomes MISSESTRUCH 2020 Histone
Linear
Pairs of matching chromosomes are called homologous pairs
Nucleus
(for example the two copies of chromosome 1 are homologous
pairs). A homologous pair of chromosomes are exactly the
same size, and have exactly the same genes but they might have
different alleles.
Humans have 23 homologous pairs
DNA storage in eukaryotic cells
DNA is stored as chromosomes
inside the nucleus.
Cell
The chromosomes are linear in
shape. The DNA is tightly coiled
and wrapped around proteins
called histones to create the
chromosome.
2 MISSESTRUCH 2020
, DNA, GENES & CHROMOSOMES Key Terms
3.4 GENETIC INFORMATION, VARIATION & RELATIONSHIPS Supercoil
BETWEEN ORGANISMS
Prokaryote
DNA storage in prokaryotes MISSESTRUCH 2020 Mitochondria
Chloroplast
Prokaryotes also carry DNA but the DNA molecules are shorter Circular
and circular. The DNA is not wound around histones. Instead,
it supercoils to fit in the cell.
DNA in mitochondria and
chloroplasts
There is also additional DNA in
mitochondria and chloroplasts found
in eukaryotic cells.
This DNA is similar to prokaryotic
DNA, in that it is short and circular.
3 MISSESTRUCH 2020
3.4 GENETIC INFORMATION, VARIATION & RELATIONSHIPS Gene
BETWEEN ORGANISMS
Locus
Gene MISSESTRUCH 2020 Allele
Chromosome
A gene is a section of DNA that contains a code for making
DNA
a polypeptide and functional RNA. The code is a specific
sequence of bases. Polypeptides make proteins and so genes
determine the proteins of an organism.
The location of a particular gene on a chromosome is called the locus.
Allele Chromosome
An allele is one of a number of alternative forms In a eukaryotic cell nucleus, DNA is stored as
of a gene. Most genes occur in two (an allelic chromosomes. Humans have 23 pairs of
pair), but occasionally in more different forms chromosomes and 46 in total.
(multiple alleles).
1
MISSESTRUCH 2020
,DNA, GENES & CHROMOSOMES Key Terms
3.4 GENETIC INFORMATION, VARIATION & RELATIONSHIPS Homologous chromosome
BETWEEN ORGANISMS
Chromosome
Homologous Chromosomes MISSESTRUCH 2020 Histone
Linear
Pairs of matching chromosomes are called homologous pairs
Nucleus
(for example the two copies of chromosome 1 are homologous
pairs). A homologous pair of chromosomes are exactly the
same size, and have exactly the same genes but they might have
different alleles.
Humans have 23 homologous pairs
DNA storage in eukaryotic cells
DNA is stored as chromosomes
inside the nucleus.
Cell
The chromosomes are linear in
shape. The DNA is tightly coiled
and wrapped around proteins
called histones to create the
chromosome.
2 MISSESTRUCH 2020
, DNA, GENES & CHROMOSOMES Key Terms
3.4 GENETIC INFORMATION, VARIATION & RELATIONSHIPS Supercoil
BETWEEN ORGANISMS
Prokaryote
DNA storage in prokaryotes MISSESTRUCH 2020 Mitochondria
Chloroplast
Prokaryotes also carry DNA but the DNA molecules are shorter Circular
and circular. The DNA is not wound around histones. Instead,
it supercoils to fit in the cell.
DNA in mitochondria and
chloroplasts
There is also additional DNA in
mitochondria and chloroplasts found
in eukaryotic cells.
This DNA is similar to prokaryotic
DNA, in that it is short and circular.
3 MISSESTRUCH 2020
