Chapter 3: Genetics and Prenatal Development

Genetics

• human body contains 46 chromosomes, in 23 pairs

• Composed of DNA, which stores and transfers genetic material

Gene

Segment of DNA containing coded instructions for the growth and functioning of the organism

Genome

Entire store of hereditary info (all the genes)

Genotype

Totality of an individuals genes (underlying genes/genetic makeup)

Phenotype

Actual characteristics (observable or behavior)

Incomplete dominance

When phenotype is influences but not exclusively by dominant gene

Ex. Sickle-cell trait

Polygenic inheritance

Interactions of multiple genes rather than just one

Ex. Physical and non-physical characteristics

Sex chromosomes

• the 23rd pair of chromosomes determines male (XY) or female (XX) sex

• Males more vulnerable to x-linked recessive disorders

Heritability

Estimate of extent to which genes are responsible for differences among persons within a specific population

Passive genotype

In a biological family, parents provide both genes and environment to their children

Ex. Dad is a graphic artist it’s and daughter grows up to be architect

Evocative genotype

When a persons inherited characteristics evoke responses from others in the environment

Ex. Son is an avid reader so mom takes him to bookstore often

Active genotype

When ppl seek out environments that correspond to their genotyping characteristics

Ex. Child who is fast might run track

Ovum

Egg, reproductive cell

Gametes

Reproductive cells

Sperm and ovum

Mitosis

Process of cell replication in which chromosomes duplicate themselves and 1 cell divides into 2 identical cells

Meiosis

Duplication and division in which 4 new, non identical cells are related rom the original cell, each w 23 single chromosomes

Important sex differences

Males- outcome produces 4 viable sperm, meiosis completed before sperm are released

Females- outcome produces 1 viable egg, meiosis NOT completed until egg is fertilized

Fertilization

• for conception to occur, there must be a released ovum and a sperm

• Ovulation releases the ovum into a fallopian tube

Follicle

Ovum plus supporting cells that provide nutrients

The germinal period (First 2 weeks)

• during travel from fallopian tube to uterus, cell division takes place

• 1 week after conception, ball of 100 cells formed, called blastocyst

Amnion

Fluid-filled membrane in the womb

Placenta

The organ that allows nutrients to pass from the mother to the organism and acts as a gatekeeper to protect it from bacteria and waste in the mothers blood

Gestation

Time elapsed since conception

Differentiation in the embryonic disk

Embryonic layers

Ectoderm

Becomes kin, hair, nails, sensory organs, and the nervous system

Mesoderm

Becomes the muscles, bones, reproductive system, and the circulatory system

Endoderm

Becomes the digestive system and respiratory system

Neural tube

Forms the spinal cord and brain, develops by week 3

The fetal period

• end of 3rd trimester

• Gain 5 pounds

• Maternal stress can impact fetus

Malnutrition

• most common teratogen worldwide

• Two key vitamins are iron and iodine

Alcohol

• widespread issues in development countries

• Can lead to fetal alcohol spectrum disorder

Chromosomal disorders

• occurs because of an issue during meiosis → chromosomes fail to provide properly

• Results in too many of too few chromosomes in each cell of the zygote

• Two main types: sex chromosomes disorders and Down syndrome