Genetics
February 18, 2021
Genetics: attempt to explain the process of heredity
1 Genes, chromosomes and mutations
• Gene: heritable factor that consists of a section of DNA and influences
a characteristic.
• Locus: specific position in a chromosome occupied by a gene.
• Alleles: different forms of the same gene. Example: the gene coding
for eye color can present itself in different forms, like blue eyes, green
eyes, etc. Each form is an allele of that gene.
in practice: two alleles of the same gene occupy the same locus of two
chromosomes of an homologous pair.
• Mutation: error during DNA transcription that causes a change in
the base sequence.
Example: Sickle Cell Disease: mutation of the gene that makes hemoglobin.
The mutated allele codes for the production of glutamic acid instead of
valine. Results in sickle shaped red blood cells.
• Genome: all base sequences in an organism’s genetic information (all
cells of an organism carry the whole genome)
human genome project: research project with the goal of finding all base
sequences in human DNA. Revealed that a) 99.9% of the human genome is
the same for all humans, and b) 0.1% of the human genome is unique to
each human.
1
, CHROMOSOMES
• In prokaryotes: one circular loop of naked DNA + plasmids(additional
genetic material in small circular units)
Singular chromosomes (asexual reproduction)
• In Eukaryotes: linear DNA wrapped around histone proteins
chromosomes in pairs (sexual reproduction)
Function: organize DNA
in humans: 46 chromosomes (organizes in 23 pairs)
44 autosomal chromosomes (not responsible for sex)
2 sex chromosomes (X or Y, XX = female, XY = male)
• diploid cell: chromosomes in pairs (2n),
eukaryotic somatic cells (reproduce through mitosis)
• haploid cell: singular chromosomes (n)
gametes (reproduce through meiosis)
Chromosomes visualization:
Karyogram: shows chromosome’s size, color, shape.
Karyotype: diagnosis based on karyogram (ex: individual’s sex)
2
February 18, 2021
Genetics: attempt to explain the process of heredity
1 Genes, chromosomes and mutations
• Gene: heritable factor that consists of a section of DNA and influences
a characteristic.
• Locus: specific position in a chromosome occupied by a gene.
• Alleles: different forms of the same gene. Example: the gene coding
for eye color can present itself in different forms, like blue eyes, green
eyes, etc. Each form is an allele of that gene.
in practice: two alleles of the same gene occupy the same locus of two
chromosomes of an homologous pair.
• Mutation: error during DNA transcription that causes a change in
the base sequence.
Example: Sickle Cell Disease: mutation of the gene that makes hemoglobin.
The mutated allele codes for the production of glutamic acid instead of
valine. Results in sickle shaped red blood cells.
• Genome: all base sequences in an organism’s genetic information (all
cells of an organism carry the whole genome)
human genome project: research project with the goal of finding all base
sequences in human DNA. Revealed that a) 99.9% of the human genome is
the same for all humans, and b) 0.1% of the human genome is unique to
each human.
1
, CHROMOSOMES
• In prokaryotes: one circular loop of naked DNA + plasmids(additional
genetic material in small circular units)
Singular chromosomes (asexual reproduction)
• In Eukaryotes: linear DNA wrapped around histone proteins
chromosomes in pairs (sexual reproduction)
Function: organize DNA
in humans: 46 chromosomes (organizes in 23 pairs)
44 autosomal chromosomes (not responsible for sex)
2 sex chromosomes (X or Y, XX = female, XY = male)
• diploid cell: chromosomes in pairs (2n),
eukaryotic somatic cells (reproduce through mitosis)
• haploid cell: singular chromosomes (n)
gametes (reproduce through meiosis)
Chromosomes visualization:
Karyogram: shows chromosome’s size, color, shape.
Karyotype: diagnosis based on karyogram (ex: individual’s sex)
2
