HD EX 1 DISEASES PRESENTED AT BIRTH (4) Flashcards
3 types of diseases presented at birth:
- Chromosomal Aberrations
- Genetic Defects
- Congenital Defects
CHROMOSOMAL ABERRATIONS:
Each cell has how many chromosomes (except gamate cells)?
23 pairs = 46 chromosomes
How many chromosomes do gamate cells have?
23 chromosomes
Chromosome slide shows:
normal male karyotype.
What are the 22 pairs called? What is the 23rd pair called?
1-22 is autosomes. 23rd is the sex-linked chromosome.
What is trisomy?
Extra chromosome.
Down Syndrome is called…
Trisomy-21. There is an extra 21st chromosome.
What are characteristics of down syndrome?
Slanted eyes with round face.
Short, stocky stature.
Learning deficiency yet extremely good disposition.
Sub-par immune system so tend to be sickly.
Usually develop Alzheimer’s if survive to age 60.
Klinefelter’s Syndrome is called…
Trisomy-23. There is an extra 23rd sex chromosome = XXY.
What are characteristics of Klinefelter’s Syndrome?
Male genitalia at birth.
Secondary female traits during puberty like gynecomastia (breast tissue) and pelvic girdle widens.
Some learning impairment.
Usually are sterile.
Turner’s Syndrome is called…
Monosomy-23. There is only one sex chromosome = Xo. This individual only has 45 total chromosomes.
What are characteristics of Turner’s syndrome?
Female genitalia at birth.
Minimal changes at puberty like lack of breast development, pelvis does not widen, and sterile.
Very bright!
Turner’s responds to hormone therapy if diagnosed early enough and can become fertile again and have kids.
GENETIC DEFECTS:
What is autosomal recessive genetic disease?
Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families. It can happen on any of the 1-22 chromosomes (not the 23rd sex chromosome).
Genes line up in pairs in the…
chromosomes.
Each gene of the pair is referred to as an…
allele.
Alleles can be…
dominant or recessive.
Dominant means…
always manifests no matter what other allele it is paired with.
Recessive means…
has to be paired with another recessive allele to manifest.
What are the 3 possible gene pairing combinations?
- Homozygous Dominant: Both alleles are the same and dominant. Dominant is expressed.
- Homozygous Recessive: Both alleles are the same and recessive. Recessive is expressed.
- Heterozygote: Dominant allele and Recessive allele. The dominant is expressed but the recessive allele is still carried.
BB
Homozygous Dominant
bb
Homozygous Recessive
Bb
Heterozygote
If 2 heterozygotes mate what are the chances of transmission of a recessive disorder to their child, chance of carrier child, chance of a “normal” child?
25% chance of an affected child.
50% chance of a carrier child.
25% chance of a “normal” child.
When do most autosomal recessive disorders occur?
When heterozgotes (carriers) mate. Because carriers don’t express the trait they do not know they have it.