Ch 2 Genetics and Prenatal Development

Chromosome

Sausage-shaped structure in the nucleus of cells, containing genes, which are paired, except in reproductive cells

DNA

Stores and transfers genetic info in all life forms

Gene

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

Genome

Entire store of an organism's hereditary info

Genotype

- Info within a gene OR genetic makeup

- Inherited

- Organism's unique genetic

inheritance

ex: Rr (red flower)

Phenotype

- PHYsical expression of genes/characteristics

- Not inherited

- Organism's actual characteristics, derived from its genotype

ex: red flower

Dominant-recessive inheritance

Pattern of inheritance in which a pair of chromosomes contains one dominant and one recessive gene, but only the dominant gene is expressed in the phenotype

Allele

On a pair of chromosomes, each of 2 forms of a gene

Incomplete dominance

Form of dominant-recessive inheritance in which the phenotype is influenced primarily by the dominant gene but also to some extent by the recessive gene

Polygenic inheritance

Expression of phenotypic characteristics due to the interaction of multiple genes

Regulator gene

Gene that directs the activities of other genes

Gene therapy

Method of treating genetic disorders that involves replacing the affected genes with genes that do not have the disorder

Sex chromosomes

Male XY or female XX

X-linked inheritance

Pattern of inheritance in which a recessive characteristic is expressed b/c it's carried on the male's X chromosome

males more vulnerable to recessive disorders carried on X chromosome

Nature-nurture debate

Whether HD is influenced main by genes or environment

Behavior genetics

HOW MUCH GENES INFLUENCE BEHAVIOR

Field in the study of HD that aims to identify extent to which genes influence behavior

Monozygotic (MZ) Twins

Same genotype

One zygote split into 2; identical twins

Dizygotic (DZ) Twins

2 ova are released by a female instead of 1, and both are fertilized by sperm

Fraternal twins

Heritability

Statistical estimate of the extent to which genes are responsible for the differences among persons within a specific population, with values ranging from 0 to 1.00

Concordance rate

Degree of similarity in phenotype among pairs of family members, expressed as a percentage

Epigenesis

GENES + ENVIRONMENT

In development, the continuous bidirectional interactions between genes and environment

Reaction range

Range of possible developmental paths established by genes

Environment determines where development takes place within that range

Theory of genotype ---> Environment effects

Theory proposing that genes influence the kind of environment we experience

Passive genotype

In theory of genotype ---> environment effects, the type that results from the fact that in a biological family,

parents provide both genes and environment to their children

Evocative genotype

In TOG ---> EE, the type that results occur when

children evoke responses from others in the environment

Active genotype

In TOG ---> EE, the type that results when

children seek out environments that correspond to their genotype

Ovum

Mature egg that develops in ovaries, about every 28 days in human females

Meiosis

Gametes are generated, through separation and duplication of chromosome pairs, ending in 4 new gametes from the original cell, each with 1/2 number of chromosomes of original cell

Mitosis

Cell replication, in which chromosomes duplicate themselves and the cell divides into 2 cells, each with same number of chromosomes as original cell

Cytoplasm

In an ovum, fluid that provides nutrients for the first 2 weeks of growth if the ovum is fertilized, until it reaches the uterus and begins drawing nutrients form the mother

Crossing over

At the outset of meiosis, the exchange of genetic material between paired chromosomes

Follicle

During the female reproductive cycle, the ovum plus other cells that surround the ovum and provide nutrients

Zygote

Following fertilization, the new cell formed form union of sperm and ovum

Germinal period

First 2 weeks after conception

Blastocyst

Ball of ~ 100 cells formed by about one week following conception

Trophoblast

In the blastocyst, the outer layer of cells, which will go on to form structures that provide protecting and nourishment to the embryo

Embryonic disk

In the blastocyst, the inner layer of cells, which will go on to form the embryo

Timeline (periods) of Prenatal Development

Germinal (1-2 weeks), embryonic (3-8), fetal (9-38)

Amnion

Fluid-filled membrane that surrounds and protects the developing organism in the womb

Placenta

In the womb, gatekeeper between mother and fetus, protects fetus from bacteria and wastes in the mother's blood, and producing hormones that maintain the blood in the uterine lining and cause the mother's breasts to produce milk

Umbilical cord

Structure connecting the placenta to the mother's uterus

Gestation

In prenatal development, elapsed time since conception

Ectoderm

In embryonic period, the outer layer of cells, which will eventually become the skin, hair, nails, sensory organs, and NS

Mesoderm

In the EP, Middle of 3 cell layers, which will become the muscles, bones, reproductive system, and circulatory system

Endoderm

In the EP, Inner layer of cells, which will become the digestive system and respiratory system

Neural tube

In the EP, the part of the ENDODERM that will become the SC and brain

Neuron

Cell of NS

Trimester

One of the three 3-month periods of prenatal development

Midwife

Someone who assists in pregnant women's prenatal care and the birth process

Down syndrome

Genetic disorder carries an extra chromosome on 21st pair

Teratogens

Behavior, environment, or bodily condition that can disrupt development of fetus

Common ones:

Malnutrition, infectious disease (rubella, AIDS), substances (alcohol leads to FASD, tobacco, other drugs)

AIDS (acquired immune deficiency syndrome)

Sexually transmitted infection caused by HIV, resulting in damage to the immune system

FASD (Fetal alcohol spectrum disorder)

Set of problems that occur as a consequence of high maternal alcohol use during pregnancy, incl. facial deformities, heart problems, misshapen limbs, and a variety of cognitive problems

Secondhand smoke

Smoke from a cigarette inhaled by those near the smoker

Ultrasound

Machine that uses sound waves to produce images of the fetus during pregnancy

Amniocentesis

Prenatal procedure in which a needle is used to withdraw amniotic fluid containing fetal cells from the placenta, allowing possible prenatal problems to be detected

Chorionic Villus Sampling (CVS)

Prenatal technique for diagnosing genetic problems, involving taking a sample of cells at 5-10 weeks gestation by inserting a tube into the uterus

Infertility

Inability to attain pregnancy after at least a year of regular sexual intercourse

Men: low quality sperm

Women: problems in ovulation

Assisted Reproductive Technologies (ART)

Methods for overcoming infertility that include artificial insemination, fertility drugs, and IVF

In vitro fertilization (IVF)

Eggs removed from your ovaries and mixed with sperm in a laboratory culture dish

Use of drugs to stimulate growth

Artificial insemination

Procedure of injecting sperm directly into the uterus

Animalcule

Microscopic human being

Infertility belt

Geographical area in central Africa w/ infertility rates as high as 30%, apparently due to high rates of malnutrition and STIs

Miscarriage

<20 weeks

Stillborn

>20 weeks

Why study twins?

Behavioral genetics (heritability rates and nature vs. nurture)

Epigenetics