2. General information
• Genetics Study of what genes are, how they
carry information, how information is
expressed, and how genes are
replicated
• Gene Segment of DNA that encodes a
functional product, usually a protein
3. • The genotype is the part (DNA sequence) of the
genetic makeup of a cell, and therefore of an
organism or individual, which determines a
specific characteristic (phenotype) of that
cell/organism/individual.
4. • The phenotype of an organism is the class to
which that organism belongs as determined by
the description of the physical and behavioral
characteristics of the organism, for example its
size and shape, its metabolic activities and its
pattern of movement.
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6. Dominant and recessive alleles
• A dominant allele produces a dominant
phenotype in individuals who have one copy of
the allele, which can come from just one parent.
For a recessive allele to produce a recessive
phenotype, the individual must have two copies,
one from each parent.
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10. • Suppose that fur color in mice is determined by a single gene.
Brown fur is dominant to white. A mouse homozygous for
brown fur was crossed with a white mouse.
12. Codominance and multiple alleles
• In codominance, both alleles have an affect on
the phenotype.
• The ABO human blood grouping is an example of
both codominance and multiple alleles.There are
three alleles – IA, IB and I. IA and IB are
codominant and both are dominant to I.This
results in four different phenotypes or blood
groups.
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15. Sex chromosomes and the control of
gender
• Humans have one pair of chromosomes that
determine whether
the person is male or female.These
chromosomes are called the sex chromosomes.
16. • Sex linkage the pattern of inheritance that is
characteristic for genes located on the X
chromosome
• The sex chromosomes not only carry the genes
that control gender, the X chromosome also
carries genes called sex linked or X-linked
genes.These genes occur only on the X
chromosome and not on theY chromosome
17. • A female who is heterozygous for a sex-linked
recessive characteristic that does not affect her
phenotype is called a carrier.
18. Hemophilia
• Lack of clotting factors
• Hemophilia A (most common type)
– Lack of clotting factor VIII
• Passed on with X chromosome
• .A female who is XHXh will be a
carrierfor hemophilia.A male who
has the recessive allele XhY will be
a hemophiliac.
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22. • A person with red–green colour blindness has
difficulty distinguishing between red and green.
Red–green colour blindness is inherited in a
similar way to hemophilia.A female who is XBXb
is a carrier for colour blindness and a male with
just one copy of the recessive allele will be colour
blind.
