conception
- Sperm and ova contain 23 chromosomes each - half of the chromosomes necessary (23 pairs or 46 chromosomes)
- Sperm cells have half x and half y sex chromosomes whereas all ova have on x sex chromosome
what is a zygote
once fertilization has occurred & the ova and sperm cells gave their 23 chromosomes.
what is the zygotic/ germinal phase
after conception the zygote undergoes rapid cell division aka mitosis for 2 weeks and lasts until the embryo is implanted into the uterus
how long does embryonic stage last
2-8 weeks
length of a fetus
from end of 8th week until birth
what is epigenetic
study of how cells control gene activity. it does not change the sequence of the building blocks in DNA but can turn on and off certain genes
ex: determines which function a cell will have ( heart, nerve, skin)
lyonization
also called X-inactivation where in early embryonic development of people with 2 X chromosomes, one of them is randomly and permanently inactivated in cells so they don’t have twice as many X chromosomes as males
x-linked conditions like
- Duchenne muscular dystrophy
- fragile X
pluripotent cells
cells have the potential to develop into many different cell types in the zygotic stage
what do specialized cells do
make different types of proteins causing cells in different tissues to have different shapes, membranes, structures and functions
genomic imprinting
one copy of a gene (from mom or dad) is expressed and the other is suppressed
[genes on maternal allele are expressed bc the male allele is imprinted and turned off vice versa]
inference with genomic imprinting can result in
- prader willi syndrome ( poor muscle tone, feeding, frequently hungry when older)
Angolan syndrome ( diff w/ speech, seizure and balance)
Metabolic and perinatal programming
- Explore the idea that environmental factors can change the way infants brain genes express themselves, way an infant develops, and may result in neurodevelopmental disorders.
ex: inadequate nutrition before conception can lead to child having high BP, heart disease or diabetes later in life
teratogens
- Factors that interfere with normal embryonic and fetal differentiation
- Effects: cleft lip, neural tube defect, septal defects and developmental disability
- Alcohol, cigarettes, cat litter, recreational drugs etc.
Most common complications of pregnancy
- Ectopic pregnancy = not in uterus
- Rh negative dx
- Group B streptococcus infection
- Preterm labour
- Low birth weight
Complications of labour and delivery
- Premature labour and delivery
- Labour that lasts too long
- Abnormal presentation of the infant in the birth canal
- Premature rupture of the membranes around the infant
- Umbilical prolapse
Complications of premature birth (born before the 37th week)
mmature lungs
* Increased risk of acquiring pneumonia
* Infections
* Jaundice
* Intraventricular hemorrhage
* Inability to maintain body temp
* Immature digestive tracks
Ultrasound
- Determine gestational stage
- Physical abnormalities
Amniocentesis
- Analysis of fluid and fetal cells in amniotic fluid
- 15-18 wks from gestation as early as the 12th week, if before 14th wk, risk of miscarriage
- Detect extra/missing chromosomes
Maternal serum screening
- 15-18 wks
- Determines risk of down syndrome/ spina bifida
- Associated w false negatives and positives
Differences between DNA and RNA
- mRNA is a copy of DNA specifically for the use of protein construction
- RNA differs from DNA as there is a ribose group rather than a deoxyribose group; thymine becomes uraceil bases, single stranded.
Percutaneous umbilical blood sampling
- analyze blood from cord
- Proteins, extra, missing or altered chromosomes
- 18 wks or older
- Cant detect neural tube defects
- Can detect hemophilia, anemia, some metabolic disorders and infections
- Miscarriage risk
- Safe but invasive.
Chronic villus sampling
- Between 10th-12th week
- Cells from placenta, looking for proteins, extra or altered chromosomes
- Risk of miscarriage
- Associated with child limb defects
Cell division
- Gametes have 23 chromosomes and somatic cells have 46 (23 pairs)
- Nondisjunction = when not all the chromosomes come apart during meiosis
- Can result in an egg or sperm having an extra chromosome or missing one
- Meiosis = sex cells, 4 daughter cells
- Mitosis = everything else, 2 daughter cells at the end of cell division
Mosaicism
- Mosaicism occurs when a person has two or more genetically different sets of cells in his or her body. These abnormal cells can begin to outnumber the normal ones and cause issues.
- People who carry somatic cells with normal diploid number (23 pairs), but has an extra one or more missing chromosomes or extra chromosomes are said to carry MORE CELL LINES
- Lyonization-mosaicism = occurs in all females (inactivation of the second x chromosome)
Mutations
- Permanent errors in DNA sequence that affect protein expression or function
- Underexpression, overexpression or complete absence of genes
- Caused by:
- small changes in DNA sequencing
-Deletions
-duplications
-Amplification
-translocations = transfer of a genetic segment to an incorrect location
-inversion = DNA gets put in backwards
-Single nucleotid polymorphisms
-Copy number variation
-Improper protein function = can change structure and physiology
