Exam 1: Chapter 3 Vocab Flashcards
gamete
a reproductive cell, sperm or egg in humans
zygote
the single cell formed from the union of two gametes (a sperm + an ovum)
gene
a small section of a chromosome; the basic unit for the transmission of heredity; consists of a string of chemicals that provide instructions for the cell to manufacture certain proteins
chromosome
one of the 46 molecules of DNA (in 23 pairs) that virtually each cell in the human body contains and that, together, contain all genes
human genome project
an international project to map the complete human genetic code
the twenty third pair
the chromosome pair that, in humans, determines sex. The other 22 pairs are autosomes, inherited equally by males and females
monozygotic twins
twins who originate from 1 zygote that splits early in development. Other monozygotic multiple births can also occur.
dizygotic twins
twin formed when 2 separate ova are fertilized by 2 separate sperm at roughly the same time
genotype
an organisms entire genetic inheritance or genetic potential
phenotype
the obervable characteristics of a person including appearance, personality, intelligence, and all other traits,
polygenetic traits
a trait that is controlled by multiple non allelic genes
include height, skin color, eye color, intelligence, and susceptibility to certain diseases.
x-linked recessive genes
a gene carried on the X chromosome. if a male inherets an x-linked recessive trait from his mother, he expresses that trait because the Y gene from his father has no counteracting gene. Females are more likely to be carriers, but less likely to express
what is a multifactorial trait?
a trait controlled by multiple factors such as genes and environment
ex.) human height: controlled by genetics but also nutrition plays a role
trisomy 21
aka down syndrome
a condition in which a person has 47 chromosomes instead of the usual 46 with 3 rather than 2 on the 21st pair. People with down syndrome typically have distinctive characteristics including facial features, heard abnormalities and language difficulties
autosomes:
22 of the 23 chromosome pairs
mitosis
the process of duplication and division in which each new cell contains 23 chromosome pairs=46 chromosomes just before cell division, the 46 duplicate and then divide to create new cells
read the section in the textbook on “chromosomal and genetic problems”
(page 78 :))
what are the different post conception tests
- preimplantation testing
- testing for pregnancy associated with PAPPA
- alpha-fetoprotein (AFP) assay
- sonogram (ultrasound)
- chorionic villi sampling
- amniocentesis
pre-implantation testing
after in vitro fertilization, one cell is removed from each zygote at the 4 or 8 cell stage and analyzed
risks and concerns:
-not entirely accurate
-requires surgery, IVF, and rapid assessment
-this delays implantation and reduces the likelihood of successful birth
-used only when couples are at high risk of known, testable genetic disorders
tests for Pregnancy Associated with Plasma Protein (PAPPA) and human chronic gonadotropin
blood tests are usually done at 11 weeks to test for those substances
risks and concerns:
-indicate normal pregnancy, but false positive and negatives can sometimes occurinq
Alpha feto-protein assay
the mothers blood is tested for the level of alpha feto-protein, now usually done at mid pregnancy; often combined with other blood tests and repeat sonogram
risks and concerns:
indicate neural tube defects, multiple embryos (both cause AFP) Normal levels change each week; interpretation requires accurate date of conception
sonogram (ultrasound)
high frequency sound waves are used to produce a ‘picture’ of the fetus as early as 8 weeks. More accurate later in pregnancy to detect less apparent problems, to confirm earlier suspicions, and anticipate birth complications
risks and concerns:
reveals problems such as small head or other body malformations, excessive fluid accumulating in the brain, down syndrome, and several other diseases
estimates fetal age and reveals multiple fetuses, placental position, useful in every pregnancy, sometimes sex is apparent
no known risks unlike x-rays
chorionic villi sampling
a sample of the chorion (part of the placenta) in obtained (via sonogram and syringe) at about 10 weeks and analyzed. The cells of the placenta are genetically identical to the cells of the fetus, this can indicate genetic and fetal abnormalities
risks and concerns:
can cause spontaneous abortion (only in 1%)
provides the same information as amniocentesis but can be performed earlier
amniocentesis
about half an ounce of the fluid inside the placenta is withdrawn at about 16 weeks. The cells are cultured and analyzed.
risks and concerns:
-spontaneous abortion cause by the syringe, but is very rare .05%)
-detects chromosomal abnormalities and other prenatal problems
-the amniotic fluid also reveals the sex of the fetus
-done later in pregnancy and takes about a week for results to develop
info on gamete selection
-ova and sperm are screened to select ones that are particularly free of problems
-requires IVF but avoids the rejection of a viable zygote
-every gamete (and every human) carries genes for some harmful conditions, so gamete selection is only useful in particular conditions are likely and genetic tests are accurate.
