Chapter 15: Foundations of Genetics: Chromosomes and Human Genetics Flashcards
what type is dominant
wild represented by a superscript +
what type is recessive
mutant
Genes located on a sex chromosome
Sex-linked Genes
Genes located on the same chromosome
Linked genes
Inherited together as a unit
linked genes
was the first person to associate a specific gene with a specific chromosome, early in the
1900s.
Thomas Hunt Morgan
what did Morgan discover?
Mendel’s heritable units
were chromosomes
Morgan studied heredity in what?
fruit flies
what chromosomes do males have?
XY
what chromosomes do females have
XX
which chromosome is longer X or Y
X
how many genes do X chromosomes have?
1,100 genes
what kind of traits do X chromosomes carry?
sexual traits as well as non-sexual traits
such as blood-clotting functions.
what kind of traits do Y chromosomes carry?
sexual traits
how many genes do Y chromosomes carry?
78 genes
This genetic disorder impairs the blood’s ability to
clot and causes prolonged bleeding.
Hemophilia
determined by genes found only on
the X chromosome
(sex linked)
A person who is what for the hemophilia
gene has the disease
homozygous
example of sex linked genes
Hemophilia
and
Color blindness
one of the 2 X chromosomes in
each cell randomly what?
condenses
what happens when one of the 2 X chromosomes in each cell condenses?
it becomes inactive
condensed X chromosome
Barr Body
when can the Barr Body be seen in nucleus?
during interphase
Genes that are located on the
same chromosome tend to be
inherited together and are called what?
linked genes
Offspring with a phenotype matching one of the
parental (P) phenotypes are called
parental types
new combinations of traits
nonparental phenotypes
Offspring with nonparental phenotypes (new
combinations of traits) are called what?
recombinant types, or recombinants
a what percent frequency of recombination is observed for any two genes on different chromosomes
50% frequency
break the physical connection between genes on the same chromosome
crossing over of homologous chromosomes
who constructed the genetic map?
Alfred Sturtevant
an ordered list of the genetic loci along a particular chromosome
genetic map
predicted that the farther apart two genes
are, the higher the probability that a crossover will
occur between them and therefore the higher the
recombination frequency
Alfred Sturtevantis
is a genetic map of a chromosome
based on recombination frequencies
linkage map
Distances between genes can be expressed as
map units
one map unit represents what?
1% recombination frequency
Map units indicate what?
relative distance and order,not precise locations of genes
Genes that are far apart on the same chromosome can have a recombination frequency near what
50%
Changes in an organisms chromosome
structure and genetic material. They
may have a positive, neutral or negative
effect on the life of the organism.
mutations
types of mutation
Deletion
Duplication
Inversion
Translocation
A fragment of the chromosome breaks off and
can be lost when the cell divides.
Deletion
The chromosome fragment attaches to its
homologous chromosome which will then carry
two copies of a certain set of genes.
Duplication
Fragment reattaches to the original
chromosome in the reverse orientation.
Inversion
Fragment of an original chromosome
joins a non-homologous chromosome.
Translocation
where individuals have one
extra or one fewer chromosome
Aneuploidy
what causes Aneuploidy
nondisjunction
most miscarriages are what?
Aneuploids
individuals have three or more
of each type of chromosome
Polyploidy
polyploidy could occur when?
if diploid zygote failed to divide
after DNA/Chromosomes were replicated = 4n,
tetraploidy
These individuals have an extra chromosome
21 (trisomy-21), but only two of all the other
chromosome types.
Down Syndrome
symptoms of Down Syndrome
- moderate to several mental impairment
- 40% develop heart defects
- abnormal development of the skeleton
- weak muscles
- speech and motor skills develop slowly
Frequency of Trisomy 21 (Down Syndrome) correlates with what?
Age of the mother
what is believed to
contribute to increased frequency on non-
disjunction.
long period of inactivity
All the eggs that a female will ever have are
present in her body when?
at the time of her birth!!!
