human genetics 3 Flashcards
phylogenetic continuity
common ancestry to all lifeforms, so we are just animal
- due to shared evolutionary history we have many characteristics and developmental processes with other living things
- extensive evidence that infants and baby animal= same innate charactersitcs
gametes and conception
- orange thing is the ovalm- ovaries
- ovam released once a month from one of two ovaries, which release a chemical substance if sperm is present.
Meiosis
- special type of cell division necessary for reproduction, meiosis produced gametes containing half the normal amount of chromosomes
- the DNA is replicated, recombined and the cell divides twice
- recombination of the chromosomal material between the homogonous chromosomes. After this the chromosome is no longer identical to the parent cell.
another example of Meiosis
-spermatogenesis produced 4 genetically distinct gamates: sperm determines one is sex because only the father has a Y chromosome to pass on
- ejaculation: 500 mill sperm- only 200 are exposed to ovum
period of Zygote
0-14 days, from conception to implantation in the wall of the uterus.
- penetrates cell when it does this, there is a chemical reaction which seals the membrane, tail of sperm falls off and contents of head gush into the Ovum.
- within hours, the nuclei of two gametes merge, producing the zygote.
- within 12 hours of fertilization, the zygote splits into two equal parts, each containing a full set of genetic material= MITOSIS,.
Mitosis
- The process of cell replication and division, in which the cell separates the chromosomes in the cell nucleus into two identical sets, in two identical nuclei.
- These two daughter cells are genetically identical to each other and their parent cell.
Meiosis (Short version)
DNA replicates and recombines, they undergo a first division with 2 daughter cells completely new, and then they half again.
Mitosis (short)
parent cell (og cell), the DNA is replicated and there is a division resulting in 2 daughter cells with 46 chromosomes identical to each other
Blastocyst
ball-like structure which contains 60-80 cells, within 2 days of conception implantation occurs between 8-14 days from conception.
- rates of success: only half of all fertilized ova are firmly implanted and as many as half of such implants are genetically abnormal or fail to develop,
- 3/4 zygotes fail to survive in the initial phase of devleopment
embryo
cell differentiation: the inner cell mass will become the embryo and the rest of the cell walls will become the amniotic sac and placenta
period of embryo
3-8 weeks, virtually all major organs are formed
period of fetus
9th week-until birth: all major organs begin to function and the developing organism grows
four support structures for the Embryo
- amnion: watertight sac that fills with fluid, acting as a cushion regulating temp and providing a weightless environment
chorion: a membrane surrounding the amnion, which eventually becomes the lining of the placenta
Allantois: forms the ambilocal cord - Yolk sac= supplies nutrients and blood circulation 2nd and 3rd week.
Inner cell mass has three layers
top layer (ecoderm)
becomes the nervous system, nails, teeth, inner ears, lens of eyes, and outer layer of skin
middle layer (Mesoderm)
Becomes the bones, muscles, circulatory system, inner layers of skin and other internal organs.
neural tube
U shape groove will form down the centre of the top layer and these tips of the U will move together and fuse creating a neural tube
identical (monozygotic) twins
same genetic makeup developing in the same system
fraternal (diygotic twins)
two eggs that happen to be release during menstral cycle, and both fertilized by the sperm
the sensory input received by the fetus
- Tactile stimulation: eg. Playing with ambylical cord
- Taste stimulation: can taste fluid
- Smell stimulation
- Hearing stimulation: mothers voice speaking.
Preference for mothers original language and
neonate associative learning
oral motor patterns and altered milk flow, cross-sensory learning, conditioning to tactile and taste stimuli
fetal learning
- habituation studies will let you know what babies prefer. eg. mothers language relative to others because of familiarity.
last 3 months of pregnancy
the central nervous system has developed enough to support fetal learning; fetal learning: habituation studies involve a decrease in response to repeated or continued stimulation until dishabituation occurs with the introduction of a novel/change in stimulus
Teratogens
45% of pregnancies will fail within the first 3 weeks: teratogens are external environmental agents which can cause damage or death during the prenatal period
critical periods of prenatal development
fetal alcohol spectrum diorder: microencephaly (small head) and malformations of heart, and limbs
- alcohol ingested in critical period of development, especially binging can affect baby
Thalidomide
- drugs used as anti morning sickness treatment during the 50s and 60s: major limb deformities if the mother took the drug between the 4th and 6th week after conception.
Rubella
link between babies being born bling and Rubella. 60-85% of babies that have rubella were born with a birth defect, in week 8 the later the mother had Rubella the less likley the baby was to get a birth defect.
effect of Teratogens
- dependent on timing of exposure
- genetics and environment
- same defect can be cause by teratogens.
