T1 - Biological and Genetic Dev.

Question 1

Describe DNA

Chromosomes

Answer 1

• Genes are part of chromosomes, (long strands of chemical substance called DNA) - therefore genes are made up of DNA.
• The letter sequence of each gene contains information on building specific molecules (such as proteins/hormones etc.)
• We have 46 chromosomes which typically group into pairs
• 23 pairs
• two sets of genes for making our characteristics
• one from mum and one from dad
• the two copies of genes in each set of chromosomes both send coded messages to influence the way the cell works
• chromosomes numbered 1-22 are autosomes

Question 2

Dominant and Recessive Genes

Co-dominant Genes

Difference between Genotype and Phenotype

Answer 2

• Dominant - when one gene is dominant in the pair
  Recessive - opposite
• Co-dominant - Sometimes each allele in the gene pair can carry the same weight and will still show up as combined physical characteristics
• A person who has an A and O gene will have the blood A - this blood group (A) is known as the phenotype.
  The genotype is the genes that produce the observable traits. (Having AO is a genotype)

Question 3

The Three Prenatal Periods:

• Germinal
• Embryonic
• Foetal

Answer 3

Germinal:

• conception until implantation of the zygote in the uterus wall (end of second week)
• rapid cell division and creation of blastocyst (when the zygote reaches the uterus, it consists of 100 cells, this balls of cells is the blastocyst)
• Creation of embryonic disc

Embryonic:

• implantation until end of 8th week
• three layers of cells created from the embryonic disc
• structural development

Foetal:

• organism takes final form and begins to function
• maturation of body parts and organs
• 8 weeks - birth
• nervous system now functions.

Question 4

Teratogens;
- what is a teratogen

Thalidomide

Maternal diseases

Characteristics of Teratogenesis

Answer 4

Teratogen = Any agent that causes a birth defect

• anti-nausea medicine that caused deformities

Maternal diseases:
- Rubella – viral infection that can cause severe defects in babies born to mothers who contract the disease in the first months of pregnancy

• Rhesus - Rh - the most frequent and destructive of a number of blood incompatibilities. It occurs when a negative mother gives birth to a positive child

Characteristics:

• cognitive impairment
• mental retardation
• impaired motor coordination
• attention
• memory
• language deficits
• physical abnormalities
• facial abnormalities

Question 5

What are Synapses

What is Myelination

Brain development in adolescence

Answer 5

Synapses are the point between two neurons that allow information to travel between different parts of the brain

• synapses organise the brain by forming pathways that connect the parts of the brain governing everything we do - from breathing and sleeping to thinking and feeling.
• we have very few at birth

Myelination - process whereby an axon is covered by a fatty substance acting as insulation.
- Myelin is the fatty tissue that forms a sheath to insulate mature brain cells, ensuring clear transmission of neurotransmitters across synapses.

• Right before puberty, brains experience a growth spurt that occurs mainly in the frontal love, which is the area that governs planning, impulse control and reasoning