Chapter 15: Chromosomal Basis of Inheritance Flashcards
Hemophilia
A sex-linked recessive trait defined by the absence of one or more clotting factors
Home it’s more likely for men to have hemophilia that women?
It’s on the X chromosome. Since women have 2 X chromosomes, they can be carriers of hemophilia, but not have it. Women require both mother and father to provide the recessive hemophilia to gain it. Men however only get when X from mom, and are hemizygous. So, if there mom passes on the X with the hemophilia they will gain hemophilia.
X - inactivation
Female mammals inherit 2 X chromosomes. 1 X chromosome becomes inactive during embryonic development
Barr Body
The inactive X condense into compact object. During embryonic development of x- inactivation
How does the egg chose which X becomes the Barr Body?
The X that becomes the Barr body is random
Where are genes found?
On sex chromosomes discovered by T.H. Morgan
How many sex chromosomes are there in humans and mammals?
2 for humans X & Y
XX: develops female, gene redundancy, like autosomal chromosomes
XY: develops male, no redundancy
What is on the Y chromosome
Few genes other than SRY
SRY
It is the sex determining region on the Y it turns on the genes for the male hormones
many effect= pleiotropy
What is on the X chromosomes?
other gene/traits beyond sex determination
mutations on X
- hemophilia
-Color blindness
Sex- Linked
Usually means X-linked, any diseases on Y is called Y-linked
more than 60 diseases on the X chromosomes
Autosomal Traits are influenced by what hormones?
Sex hormones
Gene Imprinting
the process by which only one copy of a gene in an individual (either mother or father) is expressed, while the other copy is suppressed.
X Imprinting
one of the X chromosomes “shut down” for females
Are most genes biallelic or monoallelic
Biallelic
Mom Gene –> protein Dad gene –> protein
Are some gene monoallelic or biallelic
Monoallelic
Mom Gene –> imprint Dad gene –> protein
What happens if imprinting doesn’t occur at all?
Child receives both copy of a gene from mother and father..
Recombination Data Map
Sequence of genes related to their frequency of occurrence.
The farther apart genes are located from each other on the same chromosomes the more likely…
to be separated during recombination
The closer genes are located from each other on the same chromosomes the more likely…
Greater chance their chance being inherited together.
Centimorgan
a map unit defined as 1% recombinant frequency
Linkage Map
genetic map based on genetic frequencies
When are genes considered linked?
When genes are close together on the same chromosome
