Chapter 3: Genetics and Heredity,
Principles of Hereditary Transmission
Genotype: Total endowment inherited by an individual
Phenotype: Set of traits a person actually
displays, resulting from a combination of the
person’s genotype (potential) and life
experiences that modify that potentia
A person's characteristics are created
by their genotype and their individual
experiences
Gregor Mendel
Hereditary characteristics
are determined by pairs of
particles called factors
Factors later was termed genes
Genes: the specialized sequences of molecules that form the genotype
Genes are made up of nucleotides
Nucleotides: Repeating basic building block of
DNA consisting of nitrogen-based molecules of
adenine, thymine, cytosine, and guanine
The nucleotides pair together to create DNA
DNA, deoxyribonucleic acid: Blueprint for genetic inheritance
Information provided by genes are not always the same
Alleles: Alternate form of a specific gene, provides a genetic basis for
many individual differences
Genes are transmitted from parents to
children by gametes or sex cells
Gametes: Sperm cell in males,
egg cell in females
Chromosomes were discovered around the same
time Mendel research was published
Chromosomes: Threadlike structure of DNA,
located in the nucleus of cells, which forms a
collection of genes
A karyotype: the pictorial representation of an individual's chromosomes
Looking at a karyotype one can see the autosomes
and the X & Y chromosomes (sex cells)
Autosomes: One of
twenty-two pairs of
homologous chromosomes
X chromosomes: Larger of the two chromosomes, normally
females have two and males only one
Y chromosomes: Smaller of the two chromosomes,
males have one and females have none
Watson and Crick
proposed the way
genes duplicate
and documented
the 46
chromosomes in
the human body
which led to the
mapping of human
genome
Human genome: Entire inventory of
nucleotide base pairs that compose the
genes and chromosomes of humans
Cell division and Chromosome Duplication
We were created by the uniting of the sperm
cell (23 chromosomes) and the egg (23
chromosomes) to create the zygote
Zygote: fertilized egg cell
From then on the cells begin to
divide through mitosis and meiosis
Mitosis: Process of cell
division that takes place in
most cells of the human
body and results in a full
complement of identical
material in the 46
chromosomes in each cell
Meiosis: Process
of cell division
that forms the
gametes;
normally results
in 23
chromosomes in
each human egg
and sperm cell
rather than the
full complement
of 46
Gene Expression
If both parents give the child the same
gene its homozygous but if both are
different then they are heterozygous or
both could be observed leading it to be
codominance
Homozygous: Genotype in which two alleles of a gene are
identical, have the same effect of a trait
Heterozygous: Genotype in which two
alleles of a gene are different
Codominance: Condition in which individual,
unblended characteristics of two alleles are
reflected in the phenotype.
Some genes can affect
others leading it to be
different than detected
Polygenic: Phenotypic characteristic influenced by two
or more genes
Genomic imprinting:Instances of genetic transmission
in which the expression of a gene is determined by
whether the particular allelic form has been inherited
from the mother or the father