Download Pedigrees and Chromosomal Abnormalities Notes (Genetics Test 2

PEDIGREES:
Genetic Family Histories
Women are represented with a ________.
Men are represented with a __________.
Affected individuals are shaded.
Discuss with your table partner:
In some cases, the family history can allow you to
determine a person’s genotype (the 2 alleles possessed by
the individual) in situations where you can not determine
this from phenotype alone. Remember that each parent
passes down one of their alleles to each offspring.
On the next slides determine any of the genotypes you
can from the given information. And then try to describe
two situations in which you can determine the genotype
on the following slide.
Pedigree for short eyelashes. Long eyelashes are
dominant (L). Short eyelashes is recessive (l).
What is the genotype of II-3? _____
What is the genotype of II-5? ____
What is the genotype of III-7? ____
You do not need to look at family history for an
individual to determine genotype for a _________
trait. The individual must be _________________.
If an individual has the ___________ phenotype a
family history may tell you the genotype.
They are _________________ if they have
o
______________________________________
______________________________________
o
_____________________________________
____________________________________
Discuss with your table partner:
Try the challenge question on the next slide.
To answer the question, review patterns of
inheritance of X and Y chromosomes from
father and mother to offspring.
Can it be determined from this pedigree if the PTC tasting
gene is sex-linked (X chromosome) or autosomal?
Must be ________________.
• __________________________________________
_________________________________________
• ________________________________________
_______________________________________
Errors in Meiosis
Nondisjunction is a failure of a
chromosome pair to __________
____________________. This
mistake causes the gametes to
have an ___________________
__________________________.
Recall that:
• Homologous pairs separate
during Meiosis I
• Sister chromatids separate during
Meiosis II
Nondisjunction can occur in either meiosis I or
Meiosis II. (The difference is that if it occurs in
Meiosis I all the egg/sperm produced have an
abnormal number.)
Aneuploidy- the condition having an abnormal number of
chromosomes.
When nondisjunction occurs half of the eggs/sperm produced
will have 2 copies of the chromosome and half will not have
the chromosome. (recall that gametes normally have one
copy)
If the egg or sperm with 2 copies is fertilized, the resulting
zygote (fertilized egg) will have __ copies of that
chromosome. This type of aneuploidy is called ___________.
If the egg or sperm with no copies of a chromosome is
fertilized, the resulting zygote will have ________copy. This
type of aneuploidy is called _____________.
_________________ is caused by trisomy 21.
Overview
Nondisjunction- the failure of a chromosome pair
to separate during meiosis.
Leads to
Aneuploidy- an abnormal number of chromosomes
(not a pair).
Two types
Monosomy: only having Trisomy: having three
one copy of a
copies of a chromosome.
chromosome.