Gina Brown
Genetics
The study of heredity and variation in living organisms
General Overview:
1. Every characteristic in your body (including functions) are controlled by
genes*
2. Hereditary characteristics are transferred by gametes
- During fertilization, male gamete from father & female gamete from mother
fuse to form a zygote which develops into a new organism
3. Each organism inherits certain general characteristics from its parents
which are unique to a particular species (these characteristics determine
that you are human)
- Each organism also inherits special characteristics from both parents,
making it unique
4. Genome: complete set of genes of a particular organism
- It is a copy of all the essential DNA coding required to synthesize all the
proteins needed by an organism
- Each somatic cell possesses a complete set of genetic instructions
(genes) [NB: Red blood cells are an exception; they do not have nuclei
and thus no chromosomes or genes]
5. Only certain genes are activated/switched on in specific cells (therefore,
only proteins that provide the structure & function of a particular cell, are
synthesized)
6. Each organism has its own unique gene combination that is determined by
the sequence of the nitrogenous bases on the DNA molecule
7. Scientists determine the evolutionary relationships between organisms by
studying the DNA sequences of different organisms
8. Note: 99% of all human DNA is identical – the difference of 0.1% makes
each human unique
Relevant Terminology:
Zygote Formed when two gametes fuse
Read p1: Formation of zygote
Genetics The study of inheritance of characteristics, and the
variations that can occur in them
Gene The smallest part of a chromosome that controls a
characteristic
Homologous pairs Chromosomes in a diploid cell always exist in pairs
Locus (plural: loci) The position of a gene on a chromosome
Alleles Alternative forms of the gene
Homozygous/pure When two alleles of a gene pair on homologous
breeding chromosomes are the same
Heterozygous/ If the alleles for a characteristic is different on a
1
, Gina Brown
hybrid homologous chromosome
Genome The complete set of genes in an organism
Genes Recap:
A segment of a DNA molecule that controls a specific hereditary
characteristic by means of its nitrogenous base sequence
Basic units of heredity in living organisms
Each chromosome is a linear collection of genes
Gene Pool
All the genes of every individual in an interbreeding population
Application to biodiversity:
A large gene pool indicates high genetic diversity, increased chances of
biological fitness, and survival
A small gene indicates low genetic diversity, reduced chances of acquiring
biological fitness, and increased possibility of extinction
Gene pool increases when mutations occur and survive
Gene pool decreases when population size is significantly reduced (e.g.,
famine, genetic disease, etc.)
Consequences of small gene pool: low infertility and increased probability of
acquiring genetic diseases and deformities
Gene pool gives an idea of:
1. the number of genes
2. the variety of genes
3. the type of genes existing in population
Gregor Mendel (1822-1884)
Austrian monk: entered monastery in (what
is now called) Czech Republic at age of 21
Enrolled at University of Vienna – studied
botany. Mathematics & other sciences
Began a series of experiments on garden
peas, which revealed several fundamental
principles of genetics
During Mendel’s time, many scientists
believed that the traits of a child’s parents
were blended in the offspring, producing a
child with intermediate characteristics
2
, Gina Brown
In addition, because the ova of sexually reproductive organisms are much
larger than sperm, some scientists believed that the female had a greater
influence on characteristics of offspring than males
Mendel designed studies to examine these assumptions
Over a 10-year period, he studied the inheritance in pea plants
He used pea plants to study how a particular characteristic was passed
from one generation to the next (Mendel didn’t realize this at the time, but
peas were a good choice as they show clear, observable, contrasting
traits and they are naturally self-pollinating and do not naturally cross-
pollinate)
Pea plants used had opposing characteristics (i.e., long/short stems,
smooth/wrinkled seeds, green or yellow seeds)
He studied 7 contrasting characteristics:
1. Tall and short plants
2. Smooth and wrinkled seeds
3. Yellow and green seeds
4. Inflated and constricted pods
5. Green and yellow pods
6. Purple and white flowers
7. Axial and terminal flowers
First, he tested the plants for 2 years, self-pollinating them by hand to
ensure: Plants were pure breeding (homozygous) & therefore offspring
were identical for several generations
He initially did his experiments with parent plants that were true-breeding for a
specific characteristic
True breeding: self-pollination takes place and all the offspring produced
have the same characteristic as the parent
He then performed his experiments, using forceps to self or cross-pollinate
plants that he wanted to study (he did this by cutting off the anthers,
containing pollen, and then performed cross-pollination himself, using
pollen of his own choice)
- He followed their characteristics from generation to generation
- First set of plants that are crossed in an experiment is called the first
parental generation (P1), and their offspring are called the first filial
generation (F1)
3
Genetics
The study of heredity and variation in living organisms
General Overview:
1. Every characteristic in your body (including functions) are controlled by
genes*
2. Hereditary characteristics are transferred by gametes
- During fertilization, male gamete from father & female gamete from mother
fuse to form a zygote which develops into a new organism
3. Each organism inherits certain general characteristics from its parents
which are unique to a particular species (these characteristics determine
that you are human)
- Each organism also inherits special characteristics from both parents,
making it unique
4. Genome: complete set of genes of a particular organism
- It is a copy of all the essential DNA coding required to synthesize all the
proteins needed by an organism
- Each somatic cell possesses a complete set of genetic instructions
(genes) [NB: Red blood cells are an exception; they do not have nuclei
and thus no chromosomes or genes]
5. Only certain genes are activated/switched on in specific cells (therefore,
only proteins that provide the structure & function of a particular cell, are
synthesized)
6. Each organism has its own unique gene combination that is determined by
the sequence of the nitrogenous bases on the DNA molecule
7. Scientists determine the evolutionary relationships between organisms by
studying the DNA sequences of different organisms
8. Note: 99% of all human DNA is identical – the difference of 0.1% makes
each human unique
Relevant Terminology:
Zygote Formed when two gametes fuse
Read p1: Formation of zygote
Genetics The study of inheritance of characteristics, and the
variations that can occur in them
Gene The smallest part of a chromosome that controls a
characteristic
Homologous pairs Chromosomes in a diploid cell always exist in pairs
Locus (plural: loci) The position of a gene on a chromosome
Alleles Alternative forms of the gene
Homozygous/pure When two alleles of a gene pair on homologous
breeding chromosomes are the same
Heterozygous/ If the alleles for a characteristic is different on a
1
, Gina Brown
hybrid homologous chromosome
Genome The complete set of genes in an organism
Genes Recap:
A segment of a DNA molecule that controls a specific hereditary
characteristic by means of its nitrogenous base sequence
Basic units of heredity in living organisms
Each chromosome is a linear collection of genes
Gene Pool
All the genes of every individual in an interbreeding population
Application to biodiversity:
A large gene pool indicates high genetic diversity, increased chances of
biological fitness, and survival
A small gene indicates low genetic diversity, reduced chances of acquiring
biological fitness, and increased possibility of extinction
Gene pool increases when mutations occur and survive
Gene pool decreases when population size is significantly reduced (e.g.,
famine, genetic disease, etc.)
Consequences of small gene pool: low infertility and increased probability of
acquiring genetic diseases and deformities
Gene pool gives an idea of:
1. the number of genes
2. the variety of genes
3. the type of genes existing in population
Gregor Mendel (1822-1884)
Austrian monk: entered monastery in (what
is now called) Czech Republic at age of 21
Enrolled at University of Vienna – studied
botany. Mathematics & other sciences
Began a series of experiments on garden
peas, which revealed several fundamental
principles of genetics
During Mendel’s time, many scientists
believed that the traits of a child’s parents
were blended in the offspring, producing a
child with intermediate characteristics
2
, Gina Brown
In addition, because the ova of sexually reproductive organisms are much
larger than sperm, some scientists believed that the female had a greater
influence on characteristics of offspring than males
Mendel designed studies to examine these assumptions
Over a 10-year period, he studied the inheritance in pea plants
He used pea plants to study how a particular characteristic was passed
from one generation to the next (Mendel didn’t realize this at the time, but
peas were a good choice as they show clear, observable, contrasting
traits and they are naturally self-pollinating and do not naturally cross-
pollinate)
Pea plants used had opposing characteristics (i.e., long/short stems,
smooth/wrinkled seeds, green or yellow seeds)
He studied 7 contrasting characteristics:
1. Tall and short plants
2. Smooth and wrinkled seeds
3. Yellow and green seeds
4. Inflated and constricted pods
5. Green and yellow pods
6. Purple and white flowers
7. Axial and terminal flowers
First, he tested the plants for 2 years, self-pollinating them by hand to
ensure: Plants were pure breeding (homozygous) & therefore offspring
were identical for several generations
He initially did his experiments with parent plants that were true-breeding for a
specific characteristic
True breeding: self-pollination takes place and all the offspring produced
have the same characteristic as the parent
He then performed his experiments, using forceps to self or cross-pollinate
plants that he wanted to study (he did this by cutting off the anthers,
containing pollen, and then performed cross-pollination himself, using
pollen of his own choice)
- He followed their characteristics from generation to generation
- First set of plants that are crossed in an experiment is called the first
parental generation (P1), and their offspring are called the first filial
generation (F1)
3
