What is pedigree analysis?
pedigree analysis is the study of a
particular trait inherited from one
generation to another It helps to know the
trait of inheritance for a particular feature,
and also, to understand whether the
feature is getting inherited or not.
Thus, it can be used to predict the
characteristics of the future generations of
a particular species, like color, satire,
height, etc.
❖ Common
analysis:
symbols are used in pedigree
Patterns and genetic disorders:
Introduction:
➢ Individuals that have two copies of the same
allele are referred to as homozygous.
➢ individuals that have copies of different alleles
are known as heterozygous.
➢ The inheritance patterns observed will depend
on whether the allele is found on an autosomal
chromosome or a sex chromosome, and on
whether the allele is dominant or recessive
• Autosomal dominant:
➢ One copy of a mutated gene from one parent can cause the genetic condition.
A child who has a parent with the mutated gene has a 50% chance of
inheriting that mutated gene. Men and women are equally likely to have these
mutations and sons and daughters are equally likely to inherit them.
• Autosomal recessive:
➢
A genetic condition can occur when the child inherits one copy of a mutated
gene from each parent. The parents of a child with an autosomal recessive
condition usually do not have the condition. Unaffected parents are called
carriers because they each carry one copy of the mutated gene and can pass
it to their children.
• X-linked dominant
➢ genetic traits or conditions can be passed down from parent to child through
mutations in a gene on a single X chromosome.
➢
In females (who have two X chromosomes), a mutation in a gene on one of
the X chromosomes is enough to cause the condition.
➢ In males (who only have one X chromosome), a mutation in the copy of the
gene on the single X chromosome causes the condition. Fathers cannot pass
X-linked dominant conditions to their sons, but all daughters of affected
fathers will be affected by the condition and can pass it on to their children.
X-linked recessive:
➢ genetic traits or conditions can be passed down from parent to child through
mutations in a gene on the X chromosome.
➢ In males (who only have one X chromosome), a mutation in the copy of the
gene on the single X chromosome causes the condition.
➢ Females (who have two X chromosomes) must have a mutation on both X
chromosomes to be affected by the condition.
➢
If only the father or the mother has the mutated X-linked gene, the daughters
are usually not affected and are called carriers because one of their X
chromosomes has the mutation but the other one is normal. Sons will be
affected if they inherit the mutated X-linked gene from their mother. Fathers
cannot pass X-linked recessive conditions to their sons.
❖Examples of autosomal recessive and
dominant:
➢ Autosomal recessive:
✓ Sickle cell anemia: one of a group of inherited disorders known as sickle cell
disease. It affects the shape of red blood cells, which carry oxygen to all parts
of the body.
✓ Red blood cells are usually round and flexible, so they move easily through
blood vessels. In sickle cell anemia, some red blood cells are shaped like
sickles or crescent moons. These sickle cells also become rigid and sticky,
which can slow or block blood flow.
➢ Autosomal dominant:
✓ Marfan syndrome is an inherited disorder that affects connective tissue — the
fibers that support and anchor your organs and other structures in your body.
Marfan syndrome most commonly affects the heart, eyes, blood vessels, and
skeleton. People with Marfan syndrome are usually tall and thin with unusually
long arms, legs, fingers, and toes
➢ Sex-linked recessive:
✓ Hemophilia is a rare disorder in which the blood doesn't clot in a typical way
because it doesn't have enough blood-clotting proteins (clotting factors)
➢ Sex-linked dominant:
✓ Rett syndrome is a rare genetic neurological and developmental disorder that
affects the way the brain develops. This disorder causes a progressive loss of
motor skills and language. Rett syndrome primarily affects females.
✓ Most babies with Rett syndrome seem to develop as expected for the first six
months of life.
Bibliography:
* https://www.mayoclinic.org/
* https://ncert.nic.in/textbook/pdf/lebo105.pdf
* https://www.cancer.gov/