1. genes and pre-natal development Flashcards
- Describe DNA
DNA looks like twister strand and the genes are like letters strung on each string, the letters are used like an instruction booklet. The letter sting on each strand contains information about how to build specific molecules.
Sometimes genes contain a variation, that make a gene not work properly, called mutations and these can cause range of problems.
- Describe how characteristics are inherited from our biological mother and father.
Humans have 46 pairs of chromosomes with about 23,000 genes. The 46 chromosomes in the human call are made up of 22 paired chromosomes. 1-22, 1 being the largest. There is also sex chromosomes X for women and men contribute an X or a Y. women xx men xy
The 23, 000 genes come in pairs, one gene in each pair is inherited from the persons mothers and the other from their father. A sperm and egg contain one cope of each gene needed to make up a person (23 chromosomes). When the sperm and egg are fertilied the two copies of each gene are present (46 chromosomes) new life begins.
Describe dominant and recessive genes
The two copies of genes in each set of chromosomes both send messages to influence the way the cells works. Some genes however are dominant meaning that gene will take precedence over the other, eg. Generally, Brown eye gene is dominant over blue.
if the mother has an A allele and an O allele (AO), her blood group will be A because the A is dominant. The father has two O alleles (OO), so he has the blood group O. Each one of their children has a 50 per cent chance of having blood group A (AO) and a 50 per cent chance of having blood group O (OO), depending on which alleles they inherit.
Describe Co-dominant genes
Not all genes are recessive or dominant, some are co-dominant meaning they carry equal weight, eg blood group A and B are same weight therefore someone with one copy of A also has copy of B will have blood group AB
- Understand the difference between Genotype & Phenotype
A Phenotype is the observable trait of a gene, eg, observable trait curly hair or blue eyes. Or a person with alleles AO will have blood group A.
The Genotype is the genes that produce the observable trait, eg curly hair gene or blood groups, person with phenotype A has Genotype AO. The a being dominant and therefore displaying the observable trait
describe Pre-natal; Germinal period
conception to 2 weeks, is the period of the zygote, rapid cell replication (multiplication). When the zygote reaches he uterus it consists of hundreds of cells called a blastocyst, the outer layer is called the trophoblast and it is responsible for developing tissue to support the embryo and implants to the mothers uturus to connect to maternal blood vessels, and the inner layer is the embryonic disk which contains the cells that become the embryo.
Describe Embryonic period;
from implantation to the end of the eighth week of gestation. This is a period of very rapid development, when all basic organs of the body are formed (organogenesis). The ectoderm will form the nervous system, skin and hair, the mesoderm will form the muscles, bones, circulatory system and other internal organs and the endoderm will form the digestive system, lungs, urinary tract and glands.
the first tissue to form is the ceural tube (primitive sponal cord) and by the end of the first month the brain has begun to develop, heart formed and beating, muscles, ribs, digestive system, limb buds. Then second month the embryo becomes more human like with facual features limbs, sexual development, circulatory system etc.
Describe the foetus stage
the organs take on their final form and begin to function (sometimes referred to as histogenesis). This time the foetus grows and develops by 26 weeks see movement, suck and swallowing reflexes, hear sounds, open close eyes, hair forming, lungs beginning to produce surfactin, substance that enables the lungs to inflate, almost all organs, except the CNS are fully formed and survival outside the womb is possible with exceptional medical care. Third trimester is rapid weight gain, CNS now functioning well enough to functions outside the womb, lungs are about to extract oxygen form the air and eyes have become responsive to light, brain activity indicated sleep and wakefulness
Understand the concept of a teratogen
These are agents during the pre-natal period that raise the incidence of deviations and produce malformations in the foetus, these include maternal diseases, blood disorders, diet, irradiation, drugs, abnormal temperature and oxygen levels. Also maternal characteristics such as age, emotional state and number of children previously born can influence prenatal development
what are synapses
synapses are the connections between neurons, they can be created, strengthened and disregarded. The synapses organise the brain by forming pathways that connect pathways that govern everything we to from eating, sleeping, thinking and feeling. There are very few synapses at birth, they are primarily for bodily functions.
Development of synapses occur very fast in early childhood, healthy toddler may create 2 million synapses per second. Based on the childs experiences some synapses strengthen and remain intact. But many are disregarded in a process of synapse elimination or pruning. By the time a child reaches adolescence about half their synapses have been pruned, leaving the number they will have for most of their lives.
myelination
is the white fatty tissue that forms a sheath to insulate mature brain cells, thus ensure clear transmition of neurotransmitters across synapses. Young children process information slower because their brain cells lack the myelin necessary for fast, clear nerve impulse transmission. The myelination begins in the primary motor and sensory areas and gradually progress to higher order regions thought, memories and feelings.
By age 3 babies brain has reached 90% of adult size, growth in each region depends largely on stimulation in those areas.
the contribution of genetics and environmental factors to brain development.
Plasticity to describe the brains ability to change in response to repeated stimuli. Basic control functions are less flexible then higher order controls such as thoughts and feelings. Brains respond to both genetics and experience. Babies have predisposed connections to develop speech, but if there not exposed to speech then the pathways can be disregarded, the “lose it or use it” principal. Brain adapt to the environment that it is in, if not exposed to different stimulation then the brain will not develop.
brain development in adolescence - which parts of the brain develops last?
Right before puberty, adolescent brains experience a growth spurt that occurs mainly in the frontal lobe, planning reasoning and impulse control. During teenage year the brain goes through another pruning. The myelination occurs last tin the frontal lobe, the major difference between teenage brain and adults is the frontal lobe and the myelination of that area.
